0001628280-21-003349 | 10-K | XBRL Viewer | EOS Energy Enterprises INC

Cover Page - USD ($) $ in Millions	12 Months Ended
Cover Page - USD ($) $ in Millions	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	EOS ENERGY ENTERPRISES, INC.
Entity Incorporation, State or Country Code	DE
Entity File Number	001-39291
Entity Tax Identification Number	84-4290188
Entity Address, Address Line One	3920 Park Avenue
Entity Address, City or Town	Edison
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08820
City Area Code	732
Local Phone Number	225-8400
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Public Float			$ 187
Entity Common Stock, Shares Outstanding		51,801,259
Entity Central Index Key	0001805077
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common stock, par value $0.0001 per share
Trading Symbol	EOSE
Security Exchange Name	NASDAQ
Warrants
Entity Information [Line Items]
Title of 12(b) Security	Warrants, each exercisable for one share of common stock
Trading Symbol	EOSEW
Security Exchange Name	NASDAQ

CONSOLIDATED BALANCE SHEETS - USD ($)

Dec. 31, 2020

Dec. 31, 2019

Current assets

Cash and cash equivalents

$ 121,853,000

$ 862,000

Grants receivable

131,000

326,000

Inventory

214,000

Receivable on sale of state tax attributes

4,060,000

Vendor deposits

2,390,000

252,000

Prepaid and other current assets

2,779,000

484,000

Total current assets

127,367,000

5,984,000

Property and equipment, net

5,653,000

5,316,000

Intangible assets, net

320,000

360,000

Investment in joint venture

3,736,000

589,000

Security deposit

825,000

808,000

Other assets

363,000

Total assets

138,264,000

13,057,000

Current liabilities

Accounts payable and accrued expenses

8,861,000

6,987,000

Accounts payable and accrued expenses - related parties

2,517,000

1,194,000

Provision for firm purchase commitments

1,585,000

Capital lease, current portion

11,000

13,000

Embedded derivative liability

1,681,000

Long term debt, current portion

1,071,000

76,559,000

Contract liabilities, current portion

77,000

300,000

Total current liabilities

14,122,000

86,734,000

Long term liabilities

Deferred rent

762,000

663,000

Capital lease

4,000

17,000

Long-term debt

280,000

Total long term liabilities

1,046,000

680,000

Total liabilities

15,168,000

87,414,000

COMMITMENTS AND CONTINGENCIES

CONTINGENTLY REDEEMABLE PREFERRED UNITS

109,365,000

SHAREHOLDERS' EQUITY

Common Stock, $0.0001 par value, 200,000,000 shares authorized, 48,943,082 and 3,930,336 shares outstanding at December 31, 2020 and 2019, respectively

^[1]

5,000

Contingently Issuable Common Stock

^[1]

17,944,000

Preferred stock, $0.0001 par value, 1,000,000 shares authorized, no shares outstanding at December 31, 2020 and 2019

^[1]

Additional paid in capital

^[1]

395,913,000

20,346,000

Accumulated deficit

^[1]

(290,766,000)

(204,068,000)

Total shareholders' equity (deficit)

^[1]

123,096,000

(183,722,000)

Total liabilities, contingently redeemable preferred units, and shareholders’ equity (deficit)

$ 138,264,000

$ 13,057,000

[1]	See Note 1 for discussion of reverse capitalization given effect herein

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Liquidation preference	$ 0	$ 136,816
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	48,943,082	3,930,336
Common stock, shares outstanding (in shares)	48,943,082	3,930,336
Preferred stock issued per unit (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Revenue

Revenues

$ 219

$ 496

Costs and expenses

Cost of sales

5,509

8,332

Research and development expenses

13,983

11,755

General and administrative expenses

18,883

7,710

Grant expense (income), net

913

(469)

Total costs and expenses

39,288

27,328

Operating loss

(39,069)

(26,832)

Other income (expense)

Sale of state tax attributes

4,060

Interest income (expense), net

(115)

Interest expense – related party

(23,706)

(49,708)

Loss on extinguishment of convertible notes

(6,111)

Change in fair value, embedded derivative

2,092

(716)

Change in fair value, Sponsor Earnout Shares

(8,083)

Income (loss) from equity in unconsolidated joint venture

127

(178)

Net loss

$ (68,754)

$ (79,483)

Basic and diluted loss per share attributable to common shareholders

Basic (in usd per share)

^[1]

$ (7.31)

$ (20.22)

Diluted (in usd per share)

^[1]

$ (7.31)

$ (20.22)

Weighted average shares of Common Stock

Basic (in shares)

^[2]

9,408,841

3,930,336

Diluted (in shares)

^[2]

9,408,841

3,930,336

[1]	See Note 1 for discussion of reverse capitalization given effect herein
[2]	See Note 1 for discussion of reverse capitalization given effect herein

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (DEFICIT) - USD ($)
$ in Thousands

Total

Block A Sponsor Earnout Shares

^[3]

Block B Sponsor Earnout Shares

^[4]

Common Stock

Block A Sponsor Earnout Shares

Additional Paid in capital

Block A Sponsor Earnout Shares

^[3]

Additional Paid in capital

Block B Sponsor Earnout Shares

^[4]

Contingently Issuable Common Stock

Accumulated Deficit

Beginning balance (in shares) at Dec. 31, 2018

^[1]

3,930,336

Beginning balance at Dec. 31, 2018

$ (104,374)

$ 0

^[1]

$ 20,211

$ 0

$ (124,585)

Shares issued to Restricted Units holders (in shares)

Stock-based compensation

$ 135

135

Net loss

(79,483)

Ending balance (in shares) at Dec. 31, 2019

^[1]

3,930,336

Ending balance at Dec. 31, 2019

(183,722)

^[2]

$ 0

^[1]

20,346

(204,068)

Conversion of contingently redeemable preferred units (in shares)

^[1]

14,727,844

Conversion of contingently redeemable preferred units

121,125

$ 2

^[1]

121,123

Conversion of convertible notes payable (in shares)

^[1]

10,886,336

Conversion of convertible notes payable

108,863

$ 1

^[1]

108,862

Net equity infusion from the Merger (in shares)

^[1]

18,364,805

Net equity infusion from the Merger

126,026

$ 2

^[1]

126,024

Contingently Issuable Common Stock

17,944

(17,944)

Transaction cost incurred in the Merger

(10,274)

Capital contribution - disgorgement of short swing profits

$ 432

432

Shares issued to Restricted Units holders (in shares)

174,761,000

174,761

^[1]

Stock-based compensation

$ 5,081

5,081

Release of Block A Sponsor earnout shares from restriction (in shares)

^[1],[3]

859,000

Release/Reclassification of Sponsor Earnout shares

$ 12,559

$ 11,760

$ 12,559

$ 11,760

Net loss

(68,754)

Ending balance (in shares) at Dec. 31, 2020

^[1]

48,943,082

Ending balance at Dec. 31, 2020

$ 123,096

^[2]

$ 5

^[1]

$ 395,913

$ 17,944

$ (290,766)

[1]	See Note 1 for discussion of reverse capitalization given effect herein
[2]	See Note 1 for discussion of reverse capitalization given effect herein
[3]	See Note 2 for discussion of Sponsor Earnout Shares
[4]	See Note 2 for discussion of Sponsor Earnout Shares

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (68,754)	$ (79,483)
Adjustment to reconcile net loss to net cash used in operating activities
Stock-based compensation	5,081	135
Depreciation and amortization	1,558	2,123
Impairment loss charged	0	1,590
Loss from disposal of property and equipment	31	0
(Income) Loss from equity in unconsolidated joint venture	(127)	178
Interest expense of convertible notes recognized	23,706	49,708
Loss on extinguishment of convertible notes	0	6,111
Provision for firm purchase commitment	1,585	0
Change in fair value, embedded derivative	(2,092)	716
Change in fair value, Sponsor Earnout Shares	8,083	0
Other	0	(52)
Changes in operating assets and liabilities:
Receivable on sale of state tax attributes	4,060	(4,060)
Prepaid and other assets	(1,607)	(462)
Inventory	(214)	634
Grants receivable	195	352
Vendor deposits	(593)	109
Security deposit	(17)	(64)
Accounts payable and accrued expenses	1,709	(2,210)
Accounts payable and accrued expenses-related parties	1,323	1,140
Contract liabilities	(223)	(468)
Deferred rent	99	169
Other assets	(362)	0
Net cash used in operating activities	(26,559)	(23,834)
Cash flows from investing activities
Investment in joint venture	(3,020)	(601)
Purchases of property and equipment	(3,605)	(2,299)
Net cash used in investing activities	(6,625)	(2,900)
Cash flows from financing activities
Capital lease payments	(15)	(72)
Proceeds from issuance of convertible notes payable – related party	9,009	19,346
Proceeds of short term notes payable	191	0
Repayment of short term notes payable	(97)	(1,000)
Proceeds from Paycheck Protection Program loan	1,257	0
Proceeds attributable to beneficial conversion features of convertible notes payable – related party	0	1,793
Proceeds from capital infusion in reverse recapitalization	142,345	0
Transaction cost for the reverse recapitalization	(10,274)	0
Issuance of contingently redeemable preferred units	11,759	2,031
Net cash provided by financing activities	154,175	22,098
Net increase (decrease) in cash and cash equivalents	120,991	(4,636)
Cash and cash equivalents, beginning of year	862	5,498
Cash and cash equivalents, end of year	121,853	862
Non-cash Investing and Financing Activities
Contribution of inventory to joint venture	0	167
Accrued and unpaid capital expenditures	374	93
Conversion of convertible notes to common stock in connection with merger	108,863	0
Conversion of contingently redeemable preferred stock to common stock in connection with merger	121,125	0
Receivable from disgorgement of short swing profits	432	0
Supplemental disclosures
Cash paid for interest	$ 118	$ 6

Nature of Operations and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Nature of Operations and Summary of Significant Accounting Policies

Nature of Operations and Summary of Significant Accounting PoliciesNature of Operations

Eos Energy Enterprises, Inc. (f/k/a B. Riley Merger Corp. II) (the “Company” or "Eos") designs, develops, manufactures, and sells innovative energy storage solutions for the electric utilities, and commercial and industrial end users. Eos has developed and has received patents on an innovative battery design relying on a unique zinc oxidation/reduction cycle to generate output current and to recharge. The Battery Management System (“BMS”) software uses proprietary Eos-developed algorithms and includes ambient and battery temperature sensors, as well as voltage and current sensors for the strings and the system. Eos and their partners focus on a collaborative approach to jointly develop and sell safe, reliable, long-lasting low-cost turn-key alternating current (“AC”) integrated systems using Eos’s direct current (“DC”) Battery System. The Company is also an investor in an unconsolidated joint venture (“JV”) which has the exclusive rights to manufacture the DC Battery Systems integrated with the BMS for DC Battery Systems that are sold and delivered in North America, subject to meeting certain performance targets. The Company’s major markets are integration of battery storage with solar that is connected to the utility power grid or the customer’s solar system that is not connected to the utility power grid, battery storage systems to be used by utilities to relieve congestion in the power grids and battery storage systems to assist commercial and industrial customers in reducing their peak energy usage or participating in the utilities ancillary and demand response markets. The location of the Company’s major markets are seen in North America, Europe, Africa, and Asia.

Reverse Recapitalization

The Company was incorporated as a Delaware corporation on June 3, 2019 as a publicly held special purpose acquisition company (“SPAC”) in order to acquire, through a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or similar business combination one or more businesses. On November 16, 2020 (the" Merger Date"), the Company consummated a reverse recapitalization (the "Merger") pursuant to which B. Riley Merger Corp. II ("BMRG") acquired Eos Energy Storage LLC pursuant to an agreement and plan for merger (the “Merger Agreement”) between the Company, BMRG Merger Sub, LLC, our wholly-owned subsidiary and a Delaware limited liability company (“Merger Sub I”), BMRG Merger Sub II, LLC, our wholly-owned subsidiary and a Delaware limited liability company (“Merger Sub II”), Eos Energy Storage LLC, a Delaware limited liability company (“EES”), New Eos Energy LLC, a wholly-owned subsidiary of EES and a Delaware limited liability company (“Newco”) and AltEnergy Storage VI, LLC, a Delaware limited liability company (“AltEnergy”).

In connection with the Merger, (1) Merger Sub I merged with and into Newco (the “First Merger”), whereupon the separate existence of Merger Sub I ceased, and Newco continued as the surviving company (such company, in its capacity as the surviving company of the First Merger, is sometimes referred to as the “First Surviving Company”) and became our wholly owned subsidiary; and (2) immediately following the First Merger and as part of the same overall transaction as the First Merger, the First Surviving Company merged with and into Merger Sub II, whereupon the separate existence of the First Surviving Company ceased, and Merger Sub II continued as the surviving company and our wholly owned subsidiary. Upon the closing of the business combination (the “Closing”), the Company changed its name to “Eos Energy Enterprises, Inc.”

Since BMRG was a non-operating public shell company, the current shareholders of EES have a relative majority of the voting power of the combined entity, the operations of EES prior to the acquisition comprises the only ongoing operations of the combined entity, and senior management of EES comprises the majority of the senior management of the combined entity, the Mergers have been accounted for as a capital transaction rather than a business combination. According to ASC 805 Business combination, the transaction was accounted for as a reverse recapitalization consisting of the issuance of Common Stock by Eos for the net monetary assets of BMRG accompanied by a recapitalization. Accordingly, the net monetary assets received by EES as a result of the Mergers with B. Riley have been treated as a capital infusion on the closing date. No goodwill or other intangible assets were recorded during the Merger. The consolidated assets, liabilities and results of operations of the Company are the historical financial statements of EES and the BMRG assets, liabilities and results of operations are consolidated with the Company beginning on the acquisition date. In order to reflect the change in capitalization, the historical capitalization related to EES common units have been retroactively restated based on the exchange ratio as if shares of B. Riley Common Stock had been issued as of the later of (i) the issuance date of the shares, or (ii) the earliest period presented in the accompanying consolidated financial statements.

Upon consummation of the Mergers, the former EES convertible notes and redeemable preferred units were converted to common stock of the Company. Refer to Note 12 and Note 14 for further discussion.

Unless the context otherwise requires, the use of the terms “the Company”, “we,” “us,” and “our” in these notes to the consolidated financial statements refers to Eos Energy Enterprises, Inc. and its consolidated subsidiaries.

Basis of Presentation

The financial statements include the accounts of the Company and its 100% owned direct and indirect subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). All significant intercompany transactions and balances have been eliminated in the preparation of the consolidated financial statements.

Reclassification of Prior Year Presentation

Certain prior year amounts have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the reported results of operations. Adjustment has been made to the Consolidated Balance sheets for the year ended December 31, 2019, to reclassify account payable and accrued expense to related parties and vendor deposits from prepaid and other current assets. These changes in classification also affected cash flows from operating activities for the year ended December 31, 2019 in the Consolidated Statements of Cash Flows.

Cash and Cash Equivalents

Cash and cash equivalents include cash and highly liquid investments purchased with original maturities of three months or less.

Concentration of Credit Risk

The Company maintains cash balances at FDIC-insured institutions. However, the FDIC limits may be exceeded at times. The Company has not experienced any losses on such accounts.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimates.

The most significant estimates in the accompanying financial statements include the valuation of Contingently Issuable Common stock , derivatives, the relative fair value allocation of Phase II bridge financing proceeds, the valuation of inventory, and estimated lives used for depreciation and amortization purposes.

Income Taxes and Deferred Taxes

The Company complies with the accounting and reporting requirements of FASB ASC Topic 740, Income Taxes (ASC 740). Income taxes are computed under the asset and liability method reflecting both current and deferred taxes, which reflect the tax impact of all events included in the financial statements. The balance sheet approach (i) reflects a current tax liability or asset recognized for estimated taxes payable or refundable on tax returns for the current and prior years, (ii) reflects a deferred tax liability or asset recognized for the estimated future tax effects attributable to temporary differences and carryforwards, (iii) measures current and deferred tax liabilities and assets using the enacted tax rate of which the effects of future changes in tax laws or rates are not anticipated, and (iv) reduces deferred tax assets, if necessary, by the amount of any tax benefits that, based on available evidence, are not expected to be realized.

ASC 740 prescribes a recognition threshold and a measurement attribute for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. Eos recognizes deferred tax assets only to the extent that management concludes these assets are more-likely-than-not to be realized. Significant judgement is required in assessing and estimating the more-likely-than-not tax consequences of the events included in the financial statements. Management considers all available positive and negative evidence, including future reversals of existing temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations.

The Company recognizes accrued interest and penalties related to unrecognized tax benefits, if any, as income tax expense. Eos records uncertain tax positions in accordance with ASC 740 on the basis of a two-step process in which (i) management determines whether it is more-likely-than-not that the tax position will be sustained on the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company has determined that the uncertain income tax positions at December 31, 2020 and December 31, 2019 that do not meet the more-likely-than-not threshold under ASC 740 are $322 and $— , respectively . See Note 10 for further information.

Impairment of Long — Lived Assets

The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. An assessment is performed to determine whether the depreciation and amortization of long-lived assets over their remaining lives can be recovered through projected undiscounted future cash flows. The amount of any long-lived asset impairment is measured based on fair value and is charged to operations in the period in which a long-lived assets impairment is determined by management.

Intangible Assets

Intangible assets are stated at their historical cost and amortized on a straight-line basis over their expected useful lives.

Property and Equipment, net

Equipment is stated at cost, less accumulated depreciation. Depreciation is computed on a straight-line basis over the estimate useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the improvements or the life of the lease. Maintenance and repair expenditures are expensed as incurred. Expenditures which significantly improve or extend the life of an asset are capitalized.

Revenue from Contracts with Customers

Revenue is earned from the sales, installation, and commissioning of energy storage systems and is derived from customer contracts. Revenue is recognized in an amount that reflects the consideration to which the Company expects to be entitled in exchange for transferring the promised goods and/or services to the customer, when or as the Company’s performance obligations are satisfied. For product sales of energy storage systems, the Company’s performance obligations are satisfied at the point in time when the customer obtains control of the system, which is either upon delivery of the goods at the customer’s designated location or upon the customer’s acceptance of the product after commissioning and testing at the customer’s site, depending on the specific terms of the respective contract with the customer. In addition, the corresponding installation and commissioning services related to the systems are performance obligations satisfied over time as the respective services are performed, based on an input measure of progress as labor costs relating to the installation and commissioning services are incurred. Further, extended warranties are offered by the Company and are identified as performance obligations that are satisfied over time, based on a time-lapsed measure of progress resulting in a ratable recognition of revenue over the respective warranty period. Payment terms generally include advance payments to reserve capacity and/or upon issuance of the

customer’s purchase order, shipment readiness, with the remainder upon delivery and commissioning of the system. Shipping and handling costs are included in cost of sales. Sales tax collected from customers are recorded on a net basis and therefore, not included in revenue. Sales tax is recorded as a liability (payable) until remitted to governmental authorities.

The Company may enter into sales contracts that provide for performance obligations in addition to the sale of the product, including performance guarantees and service obligations. Under these sales contracts, transaction price is allocated to the various performance obligations based on the relative stand-alone selling prices of the promised goods and services. When the stand-alone selling price is not observable, revenue is determined based on a best estimate of selling price using cost plus a reasonable margin and is recognized ratably over the period of performance.

Determination of Transaction Price

The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring products or services to the customer. The Company includes any fixed charges within its contracts as part of the total transaction price. In addition, several contracts include variable consideration such as refunds, penalties, and the customer’s right to return. The Company has concluded that its estimation of variable consideration results in an adjustment to the transaction price such that it is probable that a significant reversal of cumulative revenue would not occur in the future.

Assessment of Estimates of Variable Consideration

Many of the Company’s contracts with customers contain some component of variable consideration. The Company estimates variable consideration, such as refunds, penalties, and the customer’s right to return, using the expected value method, and adjusts transaction price for its estimate of variable consideration. Throughout the year, we update our estimate of variable consideration on a monthly basis, and adjust transaction price accordingly by recording an adjustment to net revenue and refund liability with respect to variable consideration such as penalties, refunds, and credits to customers. Therefore, management applies the constraint in its estimation of variable consideration for inclusion in the transaction price such that it is probable that a significant reversal of cumulative revenue would not occur in the future.

Practical Expedients and Exemptions

As permitted by ASC 606, the Company elected to use certain practical expedients in connection with the implementation of ASC 606. The Company treats costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset the Company would recognize is one year or less. The Company does not adjust the transaction price for significant financing components, as the Company’s contracts typically do not span more than a one year period. The election of these practical expedients results in accounting treatments that the Company believes are consistent with historical accounting policies and, therefore, these elections of practical expedients do not have a material impact on the comparability of the financial statements as no revenue was earned during the year ended December 31, 2020 and December 31, 2019.

Royalty Revenue

The Company receives sales-based royalty payments related to the licensing of intellectual property to the Company’s JV. The Company recognizes royalty revenues when the licensee sells products to third parties.

Product Warranty

Warranty obligations are incurred in connection with the sale of the Company’s products. The Company generally provides a standard warranty for a period of one to two years, commencing upon commissioning. Costs to provide for warranty obligations are estimated and recorded as a liability at the time of recording the sale. Extended warranties are identified as performance obligations in the Company’s contracts with customers, and are discussed

as part of revenue from contracts with customers. Costs incurred in satisfying the Company’s performance obligations with respect to extended warranties are recognized as expense when incurred.

Government Grants

The Company records grants received or receivable from government agencies as an offset to the related costs for which the grants are intended to compensate the Company. The costs of satisfying the Company’s obligations under the respective grant agreements are recognized as expense when incurred. Once the expenses are approved by the government agencies the Company records the grant receivable and related grant income. Grants received from government agencies for which expenses have not been incurred are included within accrued expenses.

Research and Development Expenses

Research and development costs are expensed as incurred, which include materials, supplies, salaries, benefits and other costs related to research, development and testing of products.

Rent Expense

The Company records rent expense on a straight-line basis based on the total minimum lease payments over the term of the lease. Differences between cash paid for lease payments and rent expense are recorded as Deferred rent on the Balance Sheets.

Accounts Receivable

The Company evaluates the creditworthiness of its customers. If the collection of any specific receivable is doubtful, an allowance is recorded in the allowance for doubtful accounts. The Company had $35 and $— of accounts receivable as of December 31, 2020 and 2019, with $35 and $— of allowances for doubtful accounts recorded, respectively.

Inventory

Inventories are stated at the lower of cost, which approximates cost determined on a first-in, first-out basis, or net realizable value. The Company records inventory when it takes delivery and title to the product according to the terms of each supply contract.

The Company evaluates its ending inventories for excess quantities and obsolescence. Inventories that management considers excess or obsolete are reserved. Management considers forecasted demand in relation to the inventory on hand, competitiveness of product offerings, market conditions and product life cycles when determining excess and obsolescence and net realizable value adjustments. Once inventory is written down and a new cost basis is established, it is not written back up if demand increases.

Investment in unconsolidated joint venture

The Company accounts for its investment in its unconsolidated joint venture using the equity method of accounting as it has been determined that the Company has the ability to exercise significant influence and is not otherwise required to consolidate. All significant decisions require unanimous consent of both joint venture members. Under the equity method, the investment is initially recorded at cost and subsequently adjusted for the Company’s share of equity in the joint venture’s income or loss.

The Company reviews its investments for other-than-temporary impairment whenever events or changes in business circumstances indicate that the carrying value of the investment may not be fully recoverable. Investments identified as having an indication of impairment are subject to further analysis to determine if the impairment is other than temporary and to estimate the investment’s fair value.

Stock-Based Compensation

Stock-based compensation is estimated at the grant date based on the fair value of the award and is recognized as expense over the requisite service period of the award. The Company uses the Black-Scholes option pricing model to estimate the fair value of awards, and generally these awards only have service conditions. The Company recognizes compensation cost on a straight-line basis over the requisite service period of the award, which is generally the award vesting term. For awards with performance conditions, we recognize compensation costs using an accelerated attribution method over the vesting period. Compensation costs are recognized only if it is probable that the performance condition will be satisfied. Determining the appropriate fair value model and related assumptions requires judgment, including estimating volatility of the Company’s common stock and expected terms. The expected volatility rates are estimated based on historical and implied volatilities of comparable publicly traded companies. The expected term represents the average time that the options that vest are expected to be outstanding based on the vesting provisions, which is determined through the simplified method, since the Company does not have sufficient historical experience regarding the exercise of options. The Company has elected to recognize forfeitures as incurred.

Earnings (loss) Per Share

In accordance with the provisions of FASB ASC Topic 260, Earnings per Share, basic earnings per share (“EPS”) is computed by dividing earnings available to common shareholders by the weighted average number of shares of common stock outstanding during the period. Other potentially dilutive common shares, and the related impact to earnings, are considered when calculating EPS on a diluted basis.

In computing diluted EPS, only potential common shares that are dilutive, those that reduce EPS or increase loss per share, are included. The effect of contingently issuable shares are not included if the result would be anti-dilutive, such as when a net loss is reported. Therefore, basic and diluted EPS are computed using the same number of weighted average shares for the years ended December 31, 2020 and 2019, as we incurred a net loss for such periods. The following potentially dilutive shares were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented:


	For the year ended December 31
	2020	2019
Stock Options and Restricted Units	2,185,954	392,838
Warrants	9,075,000	—
Block B Sponsor Earnout Shares subject to restrictions	859,000	—
Contingently Issuable Common Stock	2,000,000	—
Convertible Notes (if converted)	—	7,655,908
Contingent redeemable preferred units	—	12,964,231

Segments

The Company’s chief operating decision-maker (“CODM”) is its Chief Executive Officer and President. Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the CODM in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, the Company has determined that it operates in one operating and one reportable segment.

Fair Value of Financial Instruments

The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, and notes payable — related party and long term debt.

Accounting standards establish a hierarchy which prioritizes the inputs to valuation techniques used to measure fair value into three levels. The fair value hierarchy gives the highest priority to quoted market prices (unadjusted) in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.

Accounting standards require financial assets and liabilities to be classified based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the fair value of assets and liabilities and their placement within the fair value hierarchy levels.

The carrying value of cash and cash equivalents, accounts receivable, and accounts payable are considered to be representative of their fair value due to the short maturity of these instruments. The fair value of both the Company’s convertible notes payable — related party (the “Convertible Notes”) and the embedded derivative liability are classified within Level 3 of the fair value hierarchy. The Company’s outstanding long term debt are deemed to be at fair value as the interest rates on these debt obligations are materially consistent with prevailing rates.

The Company estimated the original fair value of the Contingently Issuable Common Stock based on a Monte Carlo simulation option-pricing model considering stock price of the Company, a risk free rate of 0.41% and volatility of 60% utilizing a peer group based on a five year term. This estimate was initially recorded as a distribution to shareholders and was presented as Contingently Issuable Common Stock. Upon the occurrence of a Triggering Event, any issuable shares would be transferred from Contingently Issuable Common Stock to common stock and Additional paid-in capital accounts.

Pursuant to the guidance under ASC 815, Derivatives and Hedging, the Sponsor Earnout Shares was classified as a Level 3 fair value measurement liability, and the increase or decrease in the fair value during the reporting period is recognized as expense or income accordingly. The fair values of the Sponsor Earnout Shares on the Closing date were estimated using a Monte Carlo simulation based on stock price of the Company, a risk free rate of 0.41% and volatility of 60% utilizing a peer group based on a five year term. The fair value of the first tranche of Sponsor Earnout Shares ("Block A") that vested on December 16, 2020 was based on the closing share price of the Company’s publicly traded stock on that date. The fair values of the second tranche of the Sponsor Earnout Shares ("Block B) on December 16, 2020, when the Block B shares were reclassified from liability to equity, were estimated using a Monte Carlo simulation based on stock price of the Company, a risk free rate of 0.36% and volatility of 60% utilizing a peer group based on a five- year term.

The estimated future cash flows of the Convertible Notes were discounted using a discount rate derived from an appropriate risk-free interest rate yield curve and credit spread, and the estimated repayment date. As the Company does not have a market observable credit spread, the Company obtained a range of potential credit spreads available from market observable information on entities with a comparable credit risk. As of December 31, 2019, the estimated fair value of the convertible notes payable — related party is approximately $65,942, as compared to the carrying value of approximately $76,559.

The fair value of the embedded derivatives are determined using valuation techniques that require the use of assumptions concerning the amount and timing of future cash flows, discount rates, probability of future events and redemption dates that are beyond management’s control. As of December 31, 2019, the fair value of the embedded derivative liability was $1,681.

As of December 31, 2020, all convertible notes have been converted to common stock in connection with the Merger. Refer to Note 12 for further discussion of the convertible notes payable — related party and the embedded derivatives.

Recent Accounting Pronouncements

Pursuant to the Jumpstart Our Business Startups Act (“ JOBS Act ”), an emerging growth company is provided the option to adopt new or revised accounting standards that may be issued by the FASB or the SEC either (i) within the same periods as those otherwise applicable to non-emerging growth companies or (ii) within the same time periods as private companies. The Company has elected to use the extended transition period for complying with any new or revised financial accounting standards. As a result, the Company’s financial statements may not be comparable to the financial statements of issuers who are required to comply with the effective date for new or revised accounting standards that are applicable to public companies. We also intend to continue to take advantage of some of the reduced regulatory and reporting requirements of emerging growth companies pursuant to the JOBS Act so long as we qualify as an emerging growth company.

In February 2016, the FASB issued ASU 2016-02, Leases, which will amend current lease accounting to require lessees to recognize (i) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis, and (ii) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model. The Company is an emerging growth company and would not be required to adopt this ASU No. 2016-02 until January 1, 2022. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in ASU 2016-13 will provide more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2019, the FASB issued ASU No. 2019-10 (“ASU 2019-10”), which extends the effective date for adoption of ASU 2016-13 for certain entities. As a result of the provisions in ASU 2019-10, and as the Company was a smaller reporting company as of December 31, 2020, the Company will not be required to adopt ASU 2016-13 until January 1, 2023. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements.

In December 2019, the FASB issued Accounting Standards Update No. 2019-12 – Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes, as part of its initiative to reduce complexity in the accounting standards. The amendments in ASU 2019-12 eliminate certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. This ASU is effective for public business entities for fiscal years and interim periods beginning after December 15, 2020. The adoption of this ASU does not have a material impact on the Company's consolidated financial statements.

Merger Agreement and Reverse Recapitalization

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Merger Agreement and Reverse Recapitalization

Merger Agreement

As discussed in Note 1, on November 16, 2020, BMRG and EES entered into the Merger Agreement, which has been accounted for as a reverse recapitalization. Pursuant to the Merger Agreement, the closing cash shall be no less than $110,000 minus the transaction cost incurred by BMRG and EES.

On a special meeting of the shareholders of BMRG held on November 12, 2020, holders of 6,442,195 shares of BMRG’s common stock exercised their right to redeem those shares for cash at a price of $10.10 per share, for an aggregate of approximately $65,066. The per share redemption price of $10.10 for holders of Public Shares electing redemption was paid out of BMRG’s Trust Account, which, after taking into account the redemption but before

payment of any transaction expenses, had a balance immediately prior to the Closing of approximately $111.6 million.

On November 16, 2020, immediately prior to the Closing, BMRG issued to a number of purchasers (each, a “PIPE Investor”) an aggregate of 4,000,000 shares of BMRG’s common stock (the “PIPE Shares”), for a purchase price of $10.00 per share and an aggregate purchase price of $40,000. In accounting for the reverse recapitalization, the total cash proceeds amounted to $142,345 and resulted in the issuance of 18,364,805 shares of Common Stock, as shown in the table below (dollars in thousands, expect per share amounts).


	Total Shares	Available Cash
Balance, November 15, 2020	22,525,000	$	167,411
Less redemption of BMRG shares prior to the Merger	6,442,195	$	65,066
Less Sponsor Earnout Shares subject to restriction	1,718,000	$	—
Issuance of PIPE Shares	4,000,000	$	40,000
Balance issued upon Merger with BMRG	18,364,805	$	142,345

The aggregate purchase price for EES as set forth in the Merger Agreement was $300 million. The Merger consideration was settled through the conversion of EES’ Common Units into shares of BMRG Common Stock at an issuance price of $10.00 per share. Each issued and outstanding share of the EES’ common units was automatically converted into the applicable portion of the Merger consideration with the number of shares computed based on the exchange ratio, which is one BMRG share issued to 17.35 common units of EES. As per the 2012 plan (as defined in Note 15), outstanding options to purchase shares of EES’s common units granted under the 2012 Plan automatically converted into stock options for shares of BMRG Common Stock upon the same terms and conditions that were in effect with respect to such stock options immediately prior to the Merger, after giving effect to the exchange ratio as defined above. All convertible notes and preferred units have been converted to common stock in connection with the Merger. Refer to Note 12 for further discussion of the convertible notes payable — related party and Note 14 for the discussion of the preferred units.

Contingently Issuable Common Stock

Following the closing of the Merger, and as additional consideration for the transaction, the Company will issue within five years from the closing date to each unitholder of EES its pro-rata proportion of a one-time issuance of an aggregate of 2,000,000 Shares (the “Earnout Shares” or "Contingently Issuable Common Stock"), within five business days after (i) the closing share price of the Company's shares traded equaling or exceeding $16.00 per share for any 20 trading days within any consecutive 30-trading day period during the Earnout Period or (ii) a Change of Control (or a definitive agreement providing for a Change of Control having been entered into) during the Earnout Period (each of clauses (i) and (ii), a “Triggering Event”).

The Company estimated the original fair value of the contingently issuable shares to be $17,944, which remains contingently issuable as of December 31, 2020. This balance was recorded as a distribution to shareholders and was presented as Contingently Issuable Common Stock. Upon the occurrence of a Triggering Event, any issuable shares would be transferred from Contingently Issuable Common Stock to common stock and Additional paid-in capital accounts. Any contingently issuable shares not issued as a result of a Triggering Event not being attained by the end of Earnout period will be cancelled.

On January 22, 2021, the Triggering Event for the issuance of the Earnout Shares occurred as the Company's stock price exceeded $16.00 per share for 20 trading days within a consecutive 30-trading day period during the Earnout Period.

Sponsor Earnout shares

Pursuant to the Sponsor Earnout letter signed in connection with the Merger, 1,718,000 shares of common stock issued and outstanding held by BMRG ("Sponsor Earnout Shares") were subject to certain transfer and other

restrictions, under which (a) 859,000 Sponsor Earnout Shares ("Block A Sponsor Earnout Shares") are restricted from being transferred unless and until either, for a period of five years after the Closing, (i) the share price of our common stock equals or exceeds $12.00 per share for any 20 trading days within any consecutive 30-trading day period or (ii) a change of control occurs for a share price equaling or exceeding $12.00 per share, and (b) the remaining 859,000 Sponsor Earnout Shares ("Block B Sponsor Earnout Shares") are subject to similar restrictions except that the threshold is increased from $12.00 to $16.00. If after the five year period, there are no triggering events, the Sponsor Earnout Shares will be forfeited and canceled for no consideration. If after the five year period, only the triggering event described in clause (a) above has occurred, the remaining 859,000 Sponsor Earnout Shares described in clause (b) will be forfeited and canceled for no consideration.

The Sponsor Earnout Shares were classified as a Level 3 fair value measurement liability and $16,235 was recorded as initial liability on our Balance Sheet on the Merger Date. On December 16, 2020, the Company's stock price exceeded $12.00 per share for 20 trading days within a consecutive 30-trading day period. On that date, the restrictions on all 859,000 shares of Block A Sponsor Earnout Shares were therefore lifted and the holders of these shares were no longer restricted from selling or transferring the shares under the Sponsor Earnout letter. Prior to transferring these Sponsor Earnout Shares to equity on that date, the associated liability was marked to market and the change in fair value was recorded in our Statements of Operations. The fair value of these shares was based on the closing share price of the Company’s publicly traded stock. In addition, Block B Sponsor Earnout Shares were also reclassified as equity instrument on that day due to the release of Block A Sponsor Earnout Shares from restriction. The fair value of the Block B Sponsor Earnout Shares was estimated using a Monte Carlo simulation based on the stock price of the Company, a risk free rate of 0.36% and volatility of 60% utilizing a peer group based on a five year term. For the year ended December 31, 2020, $8,083 was recorded as loss from change in fair value of Sponsor Earnout Shares in our Statements of Operations.

On January 22, 2021, as the Company's stock price exceeded $16.00 per share for 20 trading days within a consecutive 30-trading day period, Block B Sponsor Earnout Shares was released from restriction.

Revenue Recognition

12 Months Ended

Dec. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue Recognition

Contract Balances

The following table provides information about contract liabilities from contracts with customers:


	December 31, 2020		December 31, 2019		December 31, 2018
Contract liabilities	$	77	$	300	$	718

Contract liabilities primarily relate to advance consideration received from customers and deferred revenue for which transfer of control occurs, and therefore revenue is recognized, as products are delivered or services are provided. Contract balances are reported in a net contract asset or liability position on a contract-by-contract basis at the end of each reporting period.

During the year ended December 31, 2020, contract liabilities decreased $223. The Company recognized $184 of revenue during the year ended December 31, 2020 that was included in the contract liability balance at the beginning of the period.

During the year ended December 31, 2019, contract liabilities decreased $418. The Company recognized $58 of revenue during the year ended December 31, 2019 that was included in the contract liability balance at the beginning of the period.

Transaction Price Allocated to Remaining Performance Obligations

The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period:


December 31, 2020	2021		2022		2023		2024		Thereafter
Product Revenue	$	77	$	0	$	0	$	0	$	0

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Inventory	12 Months Ended
Inventory	Dec. 31, 2020
Inventory Disclosure [Abstract]
Inventory	InventoryAs of December 31, 2020 and 2019, we had finished goods of $214 and $—.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

As of December 31, 2020 and 2019, property and equipment, net consisted of the following:


	2020		2019		Useful lives
Equipment	$	7,055	$	5,910	5	—	10 years
Capital lease	201		201		5 years
Furniture	211		125		5	—	10 years
Leasehold Improvements	2,732		2,732		Lesser of useful life/remaining lease

Tooling	523		150		2	—	3 years
Total	10,722		9,118
Less: Accumulated Depreciation and Amortization	(5,069)		(3,802)
	$	5,653	$	5,316

Depreciation and amortization expense related to property and equipment was $1,518 and $2,083, during the years ended December 31, 2020 and 2019, respectively. For the year ended December 31, 2020 and 2019, impairment loss charged to Statement of Operations were $— and $1,590, respectively, primarily related to obsolete equipment relating to its prior generation battery. These expenses are reflected in cost of sales, research and development expenses and general and administrative expenses in the Statements of Operations.

Intangible Assets

12 Months Ended

Dec. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

Intangible assets consisted of various patents valued at $400, which represents the cost to acquire the patents. These patents are determined to have useful lives and are amortized into the results of operations over ten years. During the years ended December 31, 2020 and 2019, the Company recorded amortization expenses of $40 and $40, respectively, related to patents.

Estimated future amortization expense of intangible assets as of December 31, 2020 are as follows:


2021	$	40
2022	40
2023	40
2024	40
2025	40
Thereafter	120
	$	320

Investment in Unconsolidated Joint Venture	12 Months Ended
Investment in Unconsolidated Joint Venture	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Joint Venture	Investment in Unconsolidated Joint Venture In August 2019, the Company entered into an agreement with Holtec Power, Inc (“Holtec”) to form the unconsolidated joint venture HI-POWER LLC (“Hi-Power” or “JV”). The JV was formed in order to manufacture the products for all of the Company’s projects in North America. Accordingly, the Company will purchase battery storage systems and spare parts from the JV. The joint venture is in Turtle Creek, Pennsylvania. The Company’s financial commitment is $4,100 in the form of a combination of cash and special purpose manufacturing equipment. Eos’s initial ownership interest is 49%. Both the Company and Holtec sell the products manufactured by Hi-Power. The Company will earn five percent of the product price for any products manufactured by Hi-Power and sold by Holtec or its affiliates. The joint venture commenced manufacturing activities in the fourth quarter of 2020. For the year ended December 31, 2020 and 2019, contribution made to the JV were $3,020 and $768, respectively. The investment income (loss) recognized from the unconsolidated joint venture under the equity method of accounting was $127 and $(178) for the year ended December 31, 2020 and 2019, respectively. Our investment in the unconsolidated joint venture as of December 31, 2020 and 2019 was $3,736 and $589, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Commitments

On June 24, 2016, Eos entered into a long-term non-cancelable operating lease for 45,000 sq. ft. of space for its current headquarters facility in Edison, New Jersey. On April 26, 2017, Eos entered into a lease for an additional 18,000 sq. ft. of adjoining space. These leases expire in September 2026 with renewal options up to 2036. Further, these leases require monthly rent payments along with executory costs, which include real estate taxes, repairs, maintenance and insurance. In addition, the terms of the leases contain cost escalations of approximately 10% annually. The Company also has certain non-cancelable capital lease agreements for office equipment.

Total rent expense was $914 and $930, for the years ended December 31, 2020 and 2019, respectively, of which, $— and $102 was recorded as Cost of sales; $713 and $430 as Research and development expenses; and $201 and $398 as General and administrative expenses in the Statement of Operations, respectively.

Future minimum lease commitments as of December 31, 2020 are as follows:


	Operating		Capital
2021	$	685	$	14
2022	755		4
2023	825		—
2024	895		—
2025	966		—
Later years	679		—
Total minimum lease payments	$	4,805	$	18
Less amounts representing interest			3
Present value of minimum lease payments			$	15

Firm Purchase Commitments — Related Party

In July 2020, the Company entered into an $8,000 non-cancellable purchase contract with its unconsolidated joint venture partner, Hi-Power LLC, to supply batteries for existing and future sales orders. For the year ended December 31, 2020, the Company has made purchases totaling $5,496, resulting in a remaining purchase commitment of $2,504 as of December 31, 2020 under this contract.

At the end of each reporting period, the Company evaluates its non-cancellable firm purchase commitments and records a loss, if any, using a lower of cost or market approach. In assessing the potential loss provision, we use the stated contract price and expected production volume under the relevant sales contract. The Company records a purchase commitment loss if the market selling price of Gen 2.3 Battery Systems sold to customers is less than the cost to manufacture the product.

As of December 31, 2020 , the Company recorded a provision for firm purchase commitments of $1,585. The related expense has been included as a component of cost of sales in the statement of operations.

Loan commitment

In December 2020, we entered into a secured debt commitment with one of our customers to provide loan for $1,000 which matures on December 30, 2022. $100 were drawn on that commitment and recorded in other assets on the consolidated balance sheet as of December 31, 2020.

Grant Expense, Net	12 Months Ended
Grant Expense, Net	Dec. 31, 2020
Other Income and Expenses [Abstract]
Grant Expense, Net	Grant Expense, NetEos was approved for two grants by the California Energy Commission (CEC) totaling approximately $7,000. In accordance with the grant agreements, Eos is responsible for conducting studies to demonstrate the benefits of certain energy-saving technologies to utility companies and consumers in the State of California, and is entitled to receive portions of the grants based upon expenses incurred. During the years ended December 31, 2020 and 2019, Eos recorded grant expense (income), net of $913 and $(469), respectively, which comprised of grant income of $381 and $984 and grant costs of $1,294 and $515, respectively. For the year ended December 31, 2020 and 2019, the Company has received payments totaling $1,531 and $3,209. As of December 31, 2020 and 2019, the Company had $1,136 and $— deferred grant income, respectively, which was recorded in account payable and accrued expense on the Balance Sheets, as we as a receivable in the amount of $131 and $326, respectively. The expenses incurred by Eos relate to the performance of studies in accordance with the respective grant agreements, and the grants received or receivable from the CEC are recorded as an offset to the related expenses for which the grant is intended to compensate the Company.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Eos is subject to regulation under U.S. federal and U.S. state tax laws, regulations and policies. Changes to these laws or regulations may affect the Company’s tax liability, return on investments and business operations.

Earnings before income taxes

Net loss before income taxes for domestic operations for the years ended December 31, 2020 and 2019 was $(68,754) and $(79,483), respectively.

Income expense (benefit)

Income tax expense (benefit) for the years ended December 31, 2020 and 2019 was as follows:


	2020		2019
Current expense (benefit):
U.S. federal	$	—	$	—
U.S. state and local	—		—
Total current income tax (benefit) provision	—		—
Deferred expense (benefit):
U.S. federal	$	—	$	—
U.S. state and local	—		—
Total deferred income tax (benefit) provision	—		—
Total income tax (benefit) provision	$	—	$	—

Eos has no tax provision (benefit) for the periods ended December 31, 2020 and 2019 due the generation of taxable losses offset by a valuation allowance, discussed below, on the deferred tax assets.

Reconciliation of US Federal Statutory income tax rate to actual income tax rate

The reconciliation from the statutory U.S. federal income tax rate to the effective tax rate is as follows:


	2020	2019
Income (loss) before income taxes	(68,754)	(79,483)
Statutory U.S. federal income tax (21%)	(14,439)	(16,691)
State and local income tax	(3,149)	1,548
Disallowed interest expense	4,564	11,903
Non-deductible transaction cost	66	—
Non-deductible equity cost	1,698	—
Federal R&D credit	3,660	(1,002)
Uncertain tax position	322	—
Valuation allowance	7,360	4,215
Other	(82)	27
Total income tax expense	—	—
Effective tax rate	—	—

The reported income tax provision differs from the amount computed by applying the statutory US federal income tax rate of 21% to the income before income taxes primarily due to pretax losses for which no tax benefit has been provided and nondeductible interest expense for US income tax purposes.

Deferred Income Taxes

Eos records deferred income taxes to reflect the net tax effects of temporary differences, if any, between the carrying amounts of assets and liabilities for financial reporting and the amounts used for income tax purposes. The components of deferred tax assets and liabilities at December 31, 2020 and 2019 were as follows:


	2020		2019
Deferred tax assets:
NOL carryforwards	$	40,386	$	30,540
Tax credit carryforwards	1,204		4,346
Employee compensation	1,478		187
Accruals and reserves	1,743		543
Organizational costs	179		194
Transaction costs	324		—
Deferred tax assets, gross	$	45,314	35,810
Valuation allowance	(43,895)		(34,773)
Total deferred tax assets, net	$	1,419	$	1,037
Deferred tax liabilities:
Fixed assets	(1,358)		(1,010)
Investment in partnership	(61)		(27)
Deferred tax liabilities	(1,419)		(1,037)
Total deferred tax asset (liability)	—		—

Eos’s net deferred tax balances consist primarily of federal and state net operating losses (“NOLs”) available for carry forward, and research and development credits for the years ended December 31, 2020 and 2019. The deferred tax balances and related disclosures above reflect the adjusted attribute carryforwards and associated deferred tax assets post-sale of the prior years’ attributes.

During 2019, the Company participated in a tax certificate transfer program with the state of New Jersey and sold a portion of its available prior year New Jersey state NOLs, in varying amounts from tax years 2016, 2017 and 2018. The deferred tax balances and related disclosures above reflect the adjusted attribute carryforwards and associated deferred tax assets post-sale of the prior years’ attributes. The Company anticipates participating in the program for the tax year 2019, but as of the balance sheet date, no 2019 attributes had been sold.

The Company maintains a valuation allowance where it is more-likely-than-not that all or a portion of a deferred tax asset may not be realized. Changes in the valuation allowance are included in the Company’s income tax provision in the period of change. In determining whether a valuation allowance is required, the Company evaluates factors such as prior earnings history, expected future earnings, reversal of existing taxable temporary differences, carry back and carry forward periods and tax planning strategies that could potentially enhance the likelihood of the realization of a deferred tax asset. Management has determined that it is more-likely-than not that Eos will not be able to utilize its deferred tax assets at December 31, 2020 and 2019 due to a history of cumulative losses. As such, Eos has a valuation allowance against its net deferred tax assets.

The valuation allowance increased by $9,122 between December 31, 2020 and 2019. The increase was primarily attributable to an increase in NOL and tax credit carryforwards. At December 31, 2020, the valuation allowance is $43,895, of which $1,762 will be allocated to additional paid-in capital when released. The remaining valuation allowance of $42,133 will be released through continuing operations.

Net Operating Losses & Tax Credits

As of December 31, 2020 and 2019, Eos has federal research and development tax credits (“R&D credit”) of approximately $4,603 and $3,733, which begin to expire in varying amounts from 2031 – 2040 and 2032 – 2039, respectively, subject to the annual limitation described below. In addition, Eos has state R&D credits of approximately $1,131 and $613, which will expire in varying amounts from 2024 – 2027 and 2025 – 2026 for the years ended December 31, 2020 and 2019, respectively.

The Company has NOL carryforwards for tax purposes and other deferred tax assets that are available to offset future taxable income, subject to the annual limitation described below.

As of December 31, 2020 and 2019, Eos has gross federal NOL carryforwards of approximately $174,258 and $137,909. As of December 31, 2020, Eos has state NOL carryforwards of $60,206. Regarding the federal NOL for the year ended December 31, 2020, $89,051 begins to expire in varying amounts from 2032 through 2036, while $85,207 has an indefinite carryforward period. The state NOL carryforwards begin to expire in varying amounts from 2035 through 2040. The US (federal and state) operating loss carryforwards and credits may be subject to an annual limitation due to the “change in ownership” provisions of the Internal Revenue Code, and similar state provisions. The Company determined that the merger transaction (described further in Note 2 ), constitutes a change of ownership as defined under Internal Revenue Code Section 382 and Section 383. Based on management’s Section 382 Limitation Analysis, it is expected that all NOL carryforwards that existed as of the transaction date will be allowable under Section 382, however, the deferred tax asset on the Company’s NOL carryforward is offset by a full valuation allowance at December 31, 2020. Based on management’s Section 383 Limitation Analysis, it is expected that $4,530 of federal R&D credits will expire unused. As such, these credits have been written off as of December 31, 2020.

In March and December, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) and the Consolidated Appropriations Act of 2021 (the “CAA”) were signed into law in response to the Covid-19 pandemic. The CARES Act and the CAA provided several forms of tax law changes, though Eos does not anticipate that any will have a material impact on the financial statements.

Unrecognized Tax Benefits

The Company is subject to income taxes in the United States (federal and state). Significant judgment is required in evaluating the Company’s tax positions and determining Eos’s provision for income taxes. During the ordinary course of business, there are transactions and calculations for which the ultimate tax determination is uncertain. The Company records a liability for uncertain tax positions on the basis of a two-step process in which (i) management determines whether it is more-likely-than-not that the tax position will be sustained on the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority.

Eos has unrecognized tax benefits associated with uncertain tax positions as of December 31, 2020 and 2019 as follows:


	2020	2019
Gross unrecognized tax benefits as of January 1	—	—
Additions:
Current year tax positions	722
Prior year tax positions	—	—
Reduction of prior year tax positions	—	—
Settlements	—	—
Lapse of statute of limitations	—	—
Gross unrecognized tax benefits as of December 31	722	—

Included in the balance of unrecognized tax benefits at December 31, 2020 are potential benefits of nil that, if recognized, would affect the effective tax rate on income from continuing operations. The open tax years for federal and state tax returns are generally 2017 and forward. Net operating losses and R&D credits generated in closed years and utilized in open years are subject to adjustment by the tax authorities. Eos is not currently under examination by any taxing jurisdiction.

The Company regularly assesses the adequacy of its provision for income tax contingencies in accordance with ASC 740. As a result, the Company may adjust the reserves for unrecognized tax benefits for the impact of new facts and developments, such as changes to interpretation of relevant tax law, assessments from taxing authorities, settlements with tax authorities and lapses of statute of limitations.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Convertible Notes Payable During the years ended December 31, 2020 and 2019, Eos issued convertible notes payable to certain members. Refer to Note 12 for further discussion. Management fee arrangement During the years ended December 31, 2020 and 2019, the Company incurred monthly management fees to an entity owned by a board member in relation to the use of a New York City office. Total costs incurred during the year amounted to $69 and $19, respectively, which are included in General and administrative expense in the Statements of Operations. Unpaid management fees of $— and $73 are included in Accounts payable and accrued expenses-related parties as of December 31, 2020 and 2019, respectively. Accounts Payable and Accrued Expenses Accounts payable and accrued expense-related parties as of December 31, 2020 contains $138 consultant fee payable to affiliate. This line further includes $2,382 and $1,121 accruals as of December 31, 2020 and December 31, 2019 for payments under the Joint Venture agreement. Receivable from disgorgement of short swing profits As of December 31, 2020, the Company had a receivable of $432 from its affiliated company B.Riley Securities, Inc resulting from disgorgement of short swing profits, which is included in Prepaid and other current assets. See Note 16 for a detailed discussion. Vendor deposits As of December 31, 2020, vendor deposits include a balance of $278 deposits made to Hi-Power.

Convertible Notes Payable

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Convertible Notes Payable

Convertible Notes Payable -Related party

During the year ended December 31, 2020 and December 31, 2019, the Company issued Convertible notes payable with aggregate principals of $5,469 and $19,524, respectively (the “Convertible Notes”). The Convertible Notes are secured by all assets and intellectual property of the Company. AltEnergy Storage Bridge, LLC (“AltEnergy”) and its affiliates have combined beneficial ownership in the Company exceeding 10% and therefore constitute a related party of the Company, pursuant to ASC 850, Related Parties. As of December 31, 2020, AltEnergy owned approximately 14% of the Company's Common Stock and as of December 31, 2019 AltEnergy owned approximately 20% of the EES Common and Preferred Units.

The remaining note holders do not meet the definition of a related party under ASC 850. However, the Convertible Notes were issued to each of the note holders under identical terms, and AltEnergy serves as the administrative agent of all note holders under the Convertible Note agreements. Therefore, the disclosures within Note 12 encompass all of the Convertible Notes.

Phase I Convertible Notes Payable -related party

The Convertible Notes were issued on various dates through two phases. The first phase with aggregate principal of $13,529 was issued from February 2019 to May 2019 (the “Phase I Notes”), of which $4,137 was issued to AltEnergy.

The terms of the Phase I Notes are summarized as follows:

•Maturity: On or after June 30, 2019.

•Conversion Option: At any time, the Holder may elect to convert 1.15 times the outstanding principal balance into the preferred units of the Company at $1.75 per unit.

•Liquidation Amount: Repayment shall be made at the applicable liquidation amount. The Liquidation Amount applies to all repayments, with the exception of early repayments made at the Company’s option. The Liquidation Amount applicable to repayments occurring prior to June 1, 2019 is 1.5 times the outstanding principal balance. At June 1, 2019 and August 1, 2019, the multiple increases to 2.0 and 3.0 times the outstanding principal balance, respectively.

•Optional Prepayment: The Company may prepay the Phase I Notes prior to maturity at 3.0 times the outstanding principal balance.

•Conversion upon Qualified Financing: In the event that the Company issues and sells any units to investors through a Qualified Financing, on or before the date the Phase I Notes are repaid in full, resulting in aggregate gross equity proceeds of at least $25,000, the Company may at its sole option, force the Holders to convert the Liquidation Amount into the class of equity issued in the Qualified Financing. The number of units issued at conversion are variable and shall be based upon the price per unit paid in the financing. Alternatively, the Company may also elect to settle the 2019 Convertible Notes in cash.

•Holders’ put options: If an Event of Default occurs, and at the direction of 25% of the holders, repayment at the applicable Liquidation Amount becomes immediately due on demand. Any time prior to September 30, 2019, if Event of Default has not occurred, and at the direction of a majority of holders, the Liquidation Amount becomes due on demand.

In conjunction with the Phase II Note issuance, the Phase I maturity date was extended to October 31, 2019. The term extension was considered a troubled debt restructuring and did not result in a substantial modification and was accounted for as a continuation of the existing Phase I Notes. An extinguishment charge was not recognized.

2019 Phase II Convertible Notes Payable -Related party

Convertible Notes with aggregate principal of $5,995 were issued from June 2019 to December 2019 (the “2019 Phase II Notes”), of which $2,017 was issued to AltEnergy.

The terms of the Phase II Notes are identical to the Phase I Notes, except as follows:

•Maturity: On or after October 31, 2019.

•At any time, the holder may elect to convert 1.15 times the outstanding principal balance into the Preferred Unites of the Company at $0.50 per unit.

•The Liquidation Amount is 6.0 times the outstanding principal balance, regardless of the repayment date.

•Holders’ put option: If an Event of Default occurs, and at the direction of 25% of the holders, repayment at the applicable Liquidation Amount becomes immediately due on demand. If Event of Default has not occurred, Holders cannot accelerate repayment.

•2019 Phase II Notes are Senior to Phase I Notes: In the event that the Company is obligated, or elects, to repay the Convertible Notes and does not have sufficient funds to repay all Notes in full, payments shall be made in the following order: first, to the holders of Phase II Notes until each holder has received a repayment equal to 2.0 times (2.0x) the then outstanding principal balance of holder’s Phase II Notes; second, to the holders of Phase I Notes until each holder has received a repayment equal to 1.0 times (1.0x) the then outstanding principal balance of those holder’s Phase I Notes; and third, to all holders of the 2019 Convertible Notes, pro rata based on the remaining amount due to each holder pursuant to the terms and provisions of each 2019 Convertible Note held by that holder.

Concurrent to issuance of the Phase II Notes, the Company entered into subscription agreements to sell Preferred Units to the Holders equal to the principal balance of the 2019 Phase II Notes at a price of $0.50 per unit. Phase II cash proceeds totaled $11,991. The proceeds were allocated to the Phase II Notes and EES Preferred Units based on their relative fair values at the date of issuance. The Company recognized $2,031 attributable to the 2019 Phase II Preferred Units, which was recorded as a discount against the 2019 Phase II Notes. Refer to Note 14 for further discussion regarding the EES Preferred Units.

2020 Phase II Convertible Notes Payable - Related party

During the year up to the Closing date, the Company issued Convertible Notes (the “2020 Phase II Notes”) concurrently with EES Preferred Units to certain investors for aggregate cash proceeds of $10,768, including 2020 Phase II Notes of $10,598 with terms identical to the 2019 Phase II Notes, and $170 of Phase I Notes.

The proceeds were allocated to the 2020 Phase II Notes and EES Preferred Units based on their relative fair values at the date of issuance. The Company recognized $1,759 attributable to the 2020 Phase II EES Preferred Units, which was recorded as a discount against the 2020 Phase II Notes. $1,075 of the 2020 Phase II Notes were issued to AltEnergy. Refer to Note 14 for further discussion regarding the EES Preferred Units.

Beneficial Conversion Features

The conversion option on the Phase I Notes generated a beneficial conversion feature (BCF). A BCF arises when a debt or equity security is issued with an embedded conversion option that is in the money at inception

because the conversion option has an effective strike price that is less than the fair value of the underlying equity security at the commitment date. The Company recognized this BCF by allocating the intrinsic value of the conversion option to the Preferred Units, which resulted in a discount on the Phase I Notes. The Company amortized the discount into interest expense on the commitment date, as the Convertible Notes are immediately puttable by investors.

Embedded Derivatives

Both the occurrence of a Qualified Financing and the exercise of the holders’ put options represent events that can accelerate repayment of the 2019 Convertible Notes and involve a significant discount. Therefore, these features constitute embedded derivatives that require bifurcation pursuant to ASC 815-15, Embedded Derivatives.

In the event of a Qualified Financing occurring prior to July 31, 2019, the Phase I notes can be repaid at a 1.5x or 2.0x Liquidation Amount, thereby resulting in an embedded derivative at issuance. For the year ended December 31, 2020, embedded derivative assets with initial fair value of $411 was recognized. Embedded derivative assets with initial fair value of $181 and embedded derivative liabilities with initial fair value of $1,145 were recognized during 2019. These amounts were recorded as discounts on the Convertible Notes. As of December 31, 2019, the embedded derivatives were classified as current liabilities on the consolidated balance sheet and had fair values of $1,681. The embedded derivatives were fair valued through the Merger date. During the year ended December 31, 2020 and 2019, a change in fair value of embedded derivative gain of $2,092 and a loss of $716 has been recognized, respectively. The fair value of the embedded derivative was zero as of December 31, 2020 as a result of the conversion of the notes in connection of the Merger.

The Company accounted for the 2019 Convertible Notes as deeply discounted zero coupon debt instruments. The balances payable at maturity reflect liquidation multiples of 3.0 and 6.0 times the stated face value of the Phase I and 2019 Phase II Notes, respectively. The following balances were recognized upon issuance of the Convertible Notes during the years ended December 31, 2020 and 2019:


	For the year ended December 31
	2019				2020
	Phase I		Phase II		Phase I		Phase II		Total
Convertible notes payable	$	40,587	$	35,973	$	510	$	31,793	$	108,863
Discount, original issuance	(20,946)		(23,982)		(340)		(21,196)		$	(66,464)
Premium (Discount), embedded derivative	181		(1,145)		—		(411)		$	(1,375)
Discount, fair value of preferred units	—		(2,031)		—		(1,759)		$	(3,790)
Discount, beneficial conversion features	(1,799)		—		—		—		$	(1,799)
Convertible notes payable, net	$	18,023	$	8,815	$	170	$	8,427	$	35,435

Subsequent Measurement

With respect to the Phase I Notes, the holders’ put option is immediately exercisable at the 1.5 times the principal amount of the Notes. Pursuant to ASC 470-10, which states that notes with demand features should be stated at or near the amount of cash that could be required to satisfy, a corresponding portion of the discount was amortized into interest expense immediately following issuance. Additionally, the discount attributable to the BCF was immediately amortized into interest expense at issuance. The remaining discount on the Phase I Notes was amortized into interest expense using the effective interest method through July 31, 2019, the date at which the note becomes payable at 3.0 times the outstanding principal amount.

Discounts on the Phase II Notes were amortized into interest expense using the effective interest method through the stated maturity date of October 31, 2019. On October 31, 2019, the Company defaulted under the Phase

II note agreements, at which time the note holders’ put option became exercisable. Accordingly, discounts on Phase II Notes issued subsequent to October 31, 2019 were immediately amortized into interest expense upon issuance.

At issuance, the annual effective interest rates on the Phase I Notes were in excess of 400%. The Phase II Notes were issued with annual effective interest rates in excess of 1,200%. During the year ended December 31, 2020 and 2019, the Company recognized interest expense of $23,706 and $49,708 related to the Convertible Notes, respectively.

In connection with the business combination, the convertible notes were then exchanged for the common stock of the Company per the “Conversion upon Qualified Financing” term discussed above. 10,886,300 shares of common stock were issued to the notes holders based on the liquidation amount of $108.9 million as of the Merger date and purchase price of $10 per shares agreed upon in the Merger agreement. The balances attributable to the Convertible Notes immediately prior to the Merger were as follows:


	Phase 1		Phase 2		Pre-Merger balance
Convertible notes payable	$	41,097	$	67,766	$	108,863
Discount, original issuance	(21,286)		(45,178)		(66,464)
Discount, embedded derivative	181		(1,556)		(1,375)
Discount, fair value of preferred units	—		(3,790)		(3,790)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,904		50,524		73,428
Convertible notes payable, net	$	41,097	$	67,766	$	108,863

As of December 31, 2019, the total principal and accrued interest on the Phase I Notes, 2019 Phase II Notes, and 2020 Phase II Notes is equal to the applicable Liquidation Amount of 3.0, 6.0, and 6.0 times the outstanding principal, respectively. The balances attributable to the 2019 Convertible Notes on December 31, 2019 were as follows:


	Phase 1		Phase 2		December 31, 2019
Convertible notes payable	$	40,587	$	35,973	$	76,560
Discount, original issuance	(20,946)		(23,982)		(44,928)
Discount, embedded derivative	181		(1,145)		(964)
Discount, fair value of preferred units	—		(2,031)		(2,031)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,564		27,158		49,722
Convertible notes payable, net	$	40,587	$	35,973	$	76,560

As of December 31, 2019, aggregate Phase I and Phase II Notes attributable to AltEnergy totaled $24,415.

The following is a summary of the Company’s long-term indebtedness (in thousands):


	December 31, 2020		December 31, 2019
Paycheck Protection Program loan payable	$	1,257	$	—
Other		94		—
Total		1,351		—
Less: long-term debt, current portion		(1,071)		—
Long-term debt	$	280	$	—

Paycheck Protection Program

On April 7, 2020, the Company received $1,257 related to its filing under the Paycheck Protection Program and Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”). The payment terms of the note are as follows:

•No payments during the deferral period, which is defined as the ten-month period beginning on the eight weeks after the cash from the loan was received.

•Commencing one month after the expiration of the deferral period, and continuing on the same day of each month thereafter until the maturity date, the Company shall pay to JPMorgan Chase Bank, N.A. (the “Lender”), monthly payments of principal and interest, each in such equal amount required to fully amortize the principal amount outstanding on the note on the last day of the deferral period by the maturity date (twenty-four months from the date of the note, or April 7, 2022). .

•On the maturity date, the Company shall pay the Lender any and all unpaid principal plus accrued and unpaid interest plus interest accrued during the deferral period.

•The Company may prepay this note at any time without payment of any premium.

The Lender is participating in the Paycheck Protection Program to help businesses impacted by the economic impact from COVID-19. Forgiveness of this loan is only available for principal that is used for the limited purposes that qualify for forgiveness under the Small Business Administration’s (the “SBA”) requirements. To obtain forgiveness, the Company must request it and must provide documentation in accordance with the Small Business Administration (the “SBA”) requirements, and certify that the amounts the Company is requesting to be forgiven qualify under those requirements. Forgiveness of the loan is dependent upon approval of the SBA.

Long-term Debt

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Long-term Debt

Convertible Notes Payable

Convertible Notes Payable -Related party

Phase I Convertible Notes Payable -related party

The terms of the Phase I Notes are summarized as follows:

•Maturity: On or after June 30, 2019.

•Conversion Option: At any time, the Holder may elect to convert 1.15 times the outstanding principal balance into the preferred units of the Company at $1.75 per unit.

•Optional Prepayment: The Company may prepay the Phase I Notes prior to maturity at 3.0 times the outstanding principal balance.

2019 Phase II Convertible Notes Payable -Related party

Convertible Notes with aggregate principal of $5,995 were issued from June 2019 to December 2019 (the “2019 Phase II Notes”), of which $2,017 was issued to AltEnergy.

The terms of the Phase II Notes are identical to the Phase I Notes, except as follows:

•Maturity: On or after October 31, 2019.

•At any time, the holder may elect to convert 1.15 times the outstanding principal balance into the Preferred Unites of the Company at $0.50 per unit.

•The Liquidation Amount is 6.0 times the outstanding principal balance, regardless of the repayment date.

2020 Phase II Convertible Notes Payable - Related party

Beneficial Conversion Features

Embedded Derivatives


	For the year ended December 31
	2019				2020
	Phase I		Phase II		Phase I		Phase II		Total
Convertible notes payable	$	40,587	$	35,973	$	510	$	31,793	$	108,863
Discount, original issuance	(20,946)		(23,982)		(340)		(21,196)		$	(66,464)
Premium (Discount), embedded derivative	181		(1,145)		—		(411)		$	(1,375)
Discount, fair value of preferred units	—		(2,031)		—		(1,759)		$	(3,790)
Discount, beneficial conversion features	(1,799)		—		—		—		$	(1,799)
Convertible notes payable, net	$	18,023	$	8,815	$	170	$	8,427	$	35,435

Subsequent Measurement


	Phase 1		Phase 2		Pre-Merger balance
Convertible notes payable	$	41,097	$	67,766	$	108,863
Discount, original issuance	(21,286)		(45,178)		(66,464)
Discount, embedded derivative	181		(1,556)		(1,375)
Discount, fair value of preferred units	—		(3,790)		(3,790)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,904		50,524		73,428
Convertible notes payable, net	$	41,097	$	67,766	$	108,863


	Phase 1		Phase 2		December 31, 2019
Convertible notes payable	$	40,587	$	35,973	$	76,560
Discount, original issuance	(20,946)		(23,982)		(44,928)
Discount, embedded derivative	181		(1,145)		(964)
Discount, fair value of preferred units	—		(2,031)		(2,031)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,564		27,158		49,722
Convertible notes payable, net	$	40,587	$	35,973	$	76,560

As of December 31, 2019, aggregate Phase I and Phase II Notes attributable to AltEnergy totaled $24,415.

The following is a summary of the Company’s long-term indebtedness (in thousands):


	December 31, 2020		December 31, 2019
Paycheck Protection Program loan payable	$	1,257	$	—
Other		94		—
Total		1,351		—
Less: long-term debt, current portion		(1,071)		—
Long-term debt	$	280	$	—

Paycheck Protection Program

•No payments during the deferral period, which is defined as the ten-month period beginning on the eight weeks after the cash from the loan was received.

•On the maturity date, the Company shall pay the Lender any and all unpaid principal plus accrued and unpaid interest plus interest accrued during the deferral period.

•The Company may prepay this note at any time without payment of any premium.

Contingently Redeemable Preferred Units

12 Months Ended

Dec. 31, 2020

Temporary Equity Disclosure [Abstract]

Contingently Redeemable Preferred Units

As of December 31, 2019, the Company had outstanding Series C, Series D, and 2019 Bridge Preferred Units ("EES Preferred Units), which were issued at $1.10, $1.75, and $0.50 per unit, respectively.

Pursuant to the EES LLC Agreement, the rights and privileges of the EES Preferred Members were as follows:

Voting — The EES Preferred Members are entitled to vote together with the holders of EES Common Units on all matters submitted for members’ vote. Additionally, the EES Preferred Members occupy a majority of the seats of the Board of Directors and can therefore control all decisions subject to the Board’s vote.

The following actions require a majority vote of the Preferred Members:

•Pay any dividend on any EES Units

•Agree or enter into a merger, sale of a material portion of the Assets, or other corporate reorganization or acquisition or any other transaction resulting in a change of control of EES.

•Create or authorize the creation of any debt security, guarantee, or instrument with similar effect in excess of $1,000,000, outside the normal course of business.

•Enter new lines of business or exit the current line of business.

•Enter into an exclusive agreement or arrangement to manufacture or sell EES’s technology.

•Sell, assign, transfer, pledge, or encumber material technology or material intellectual property.

•Take any action which deviates from the current budget approved by the Board of Directors by more than 15%.

Preferred Liquidation Preference — In the event of the termination of EES or a Company Sale (as defined within the EES LLC agreement) the holders of the EES Preferred Units are entitled to receive for each outstanding unit an amount equal to the greater of: 1) the original issuance price per unit plus an 8% liquidation preference, accrued from the issuance date and (2) the amount which would have been payable to such EES Preferred Member had the EES Preferred Units been converted into EES Common Units in connection with a termination or Company Sale.

After payment of the Preferred Liquidation Preference, any remaining proceeds are distributed proportionally to the Common Unit holders. A Company Sale is defined as a sale of Units, sale of Assets, merger, recapitalization, reorganization or otherwise, pursuant to which one or more third parties (other than Voting Members) shall own in excess of fifty percent of the Voting Units or assets of the Company. As of December 31, 2019, the EES Preferred Liquidation Preference was $136,816. Because the occurrence of a Company Sale was not probable, the Company concluded the EES Preferred Units were not probable of becoming redeemable. Therefore, the carrying value had not been remeasured to the Preferred Liquidation Preference.

The occurrence of a Company Sale requires the approval of both the Board of Directors and Preferred Members. Therefore, the liquidation provisions are considered contingent redemption provisions as there are certain elements that are not solely within the control of the Company. Accordingly, the Preferred Units have been presented in the mezzanine section of the consolidated balance sheet.

Conversion — The Preferred Units are convertible at any time, at the option of the holder, into EES Common Units of the Company. Upon an optional conversion, distributions payable on such EES Preferred Units that have been declared but remain unpaid, shall be converted into EES Common Units. Upon the closing of a Qualified Public Offering (as defined within the EES LLC Agreement), EES Preferred Units will automatically convert to common units.

The EES Preferred Units are initially convertible on a one-to-one basis into EES Common Units, subject to certain adjustments for unit splits and combinations. The EES Preferred Units are also subject to full-ratchet, anti-dilution price protection (a “down round” provision). Under that provision, if the Company issues EES Common Units at an effective price that is less than the conversion price (the “Dilutive Price”), then the conversion price of the EES Preferred Units is automatically reduced to be equal to the Dilutive Price. The effect of that reduction is that, upon the issuance of either EES Common Units or securities convertible into EES Common Units, at a Dilutive Price, the EES Preferred Units would be convertible into a greater number of EES Common Units.

Bridge Preferred Units

As discussed at Note 12, the Company entered into subscription agreements to sell EES Preferred Units to the Holders at a price of $0.50 per unit concurrently with the issuance of the 2019 Phase II Notes, which resulted in the issuance of approximately 12,000,000 EES Preferred Units (the “2019 EES Bridge Preferred Units”). The Company recognized $2,031 attributable to the 2019 EES Bridge Preferred Units based on the allocated fair value of cash proceeds.

Upon the issuance of 2019 EES Bridge Preferred Units, the down round provision was triggered for the Series C and Series D EES Preferred Units whereby the conversion price was adjusted from $1.10 and $1.75, respectively to $0.50 per EES Common Unit, which resulted in approximately 144,200,000 additional EES Common Units being issuable upon conversion of the Series C and Series D EES Preferred Units. As the fair value a EES Common Unit was determined to be less than $0.50 on both 1) the original issuance date of the Series C and Series D EES Preferred Units and 2) immediately following the issuance of the EES Bridge Preferred Units, the down round did not trigger a BCF. Therefore, a deemed dividend was not recognized.

As of December 31, 2019, the Preferred Units were convertible into approximately 224,900,000 EES common units. Refer to Note 12 for further discussion regarding the fair value allocated to the EES Preferred Units. During the years ended December 31, 2020 and 2019, activities attributable to the EES Preferred Units was as follows:


	Preferred Units
	Units	Amount
Balance, December 31, 2018	68,716	$	105,548
Contributions allocated to EES Preferred Units	11,991	2,031
Discount on convertible notes, beneficial conversion feature	—	1,786
Balance, December 31, 2019	80,707	109,365
Contributions allocated to EES Preferred Units	10,598	1,759
Issuance of EES Preferred Units	20,000	10,000
Balance, November 16, 2020	111,305	$	121,124

In connection with the Merger on November 16, 2020, the Preferred Units were converted to 255,523,120 EES common units. 14,727,844 shares of the Company's common stock were issued to the EES Preferred Units holders.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-Based CompensationSince 2012, Eos has issued stock options to employees and certain service providers under the 2012 Eos Equity Incentive Plan (“2012 Plan”). In addition to stock options, the 2012 Plan provides for the issuance of other forms of stock-based compensation, including profit interests, unit appreciation rights and restricted units. Subsequent to the closing of the Merger, the Company approved the 2020 Equity Incentive Plan (the “2020 Incentive Plan”) and reserved 6,000,000 shares of common stock for issuance thereunder. The Incentive Plan became effective immediately upon the Closing of the Merger and all equity granted under the 2012 Plan were converted into equivalent equity under the 2020 Incentive Plan. As of December 31, 2020, the Company has stock options and restricted units issued under the 2020 Incentive Plan.

The following table summarizes stock option activity during the years ended December 31, 2020 and 2019. All stock option activity was retroactively restated to reflect the converted options. See Note 2 for the conversion in connection with the Merger.


	Shares	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (years)
Options Outstanding at December 31, 2018	303,028	$	26.20	2.8
Granted	254,882	$	9.54
Cancelled/Forfeited	(165,072)	$	27.24
Options Outstanding at December 31, 2019	392,838	$	15.09	5.4
Granted	1,972,679	$	9.07
Cancelled/Forfeited	(221,881)	$	18.57
Options Outstanding at December 31, 2020	2,143,636	$	9.19	9.5
Options Exercisable at December 31, 2020	15,859	$	26.81	1.7

As of December 31, 2020 and 2019, 3,825,176 and 87,906 shares remain for future issuance, respectively. Options vest generally over three to five years and have a term of five to ten years. During the year ended December 31, 2020, the Company granted stock options with both service and performance conditions. Stock compensation is recognized on a straight-line basis over the requisite service period of the award, which is generally the award vesting term. For awards with performance conditions, compensation expense is recognized using an accelerated attribution method over the vesting period. The performance conditions primarily relate to the completion of project milestones, achievement of operational certifications, and the Company’s closing of financing rounds.

The Company’s Restricted Units (RU) represent the right to receive one common share, subject to vesting and transferability restrictions. For the year ended December 31, 2020 and December 31, 2019, 123,478 and — RUs were granted. During the same periods, 174,761 and — common shares were issued for RUs that had fully vested during the current and prior periods. As of December 31, 2020, 42,318 RUs were outstanding and unvested. These unvested RUs include (1) 31,188 units issued to directors of our Board which will vest at the earlier of our next annual shareholders meeting or December 8, 2021 and (2) 11,130 units issued to a member of our senior management which will be vested on December 16, 2021. These RUs were measured at their grant-date fair value of $13.46 per unit and will be fully vested in 2021.

The Company recorded stock compensation expense of $5,081 for the year ended December 31, 2020 which includes $977 from RUs and $4,104 from stock options, respectively. $135 of stock compensation was recorded for the year ended December 31, 2019, including $4 from RUs and $131 from stock options, respectively. The stock compensation has been recorded in cost of sales, R&D expense and general and administrative expenses in the Statements of Operations. Unrecognized stock compensation expenses amount to $7,416 and include $472 attributable to RUs, which is expected to be recognized within one year, and $6,944 attributable to stock option, which is expected to be recognized over the next four years.

The weighted average assumptions used to determine the fair value of options granted in 2020 and 2019 are as follows:


	2020		2019
Volatility	52.99	%	58.20	%
Risk free interest rate	0.39	%	1.89	%
Expected life (years)	5.19		6.25
Dividend yield	0	%	0	%

The weighted average grant date fair value of all options granted was $5.38 and $1.21 per option for the years ended December 31, 2020 and 2019, respectively.

Shareholders' Equity	12 Months Ended
Shareholders' Equity	Dec. 31, 2020
Equity [Abstract]
Shareholders' Equity	Shareholder's Equity Preferred Shares The Company is authorized to issue 1,000,000 shares of preferred stock with such designations, voting and other rights and preferences as may be determined from time to time by the Company’s board of directors. At December 31, 2020 and 2019, there were no shares of preferred stock issued or outstanding. Common Stock The Company is authorized to issue 200,000,000 shares of common stock with $0.0001 par value. Holders of the Company’s common stock are entitled to one vote for each share. At December 31, 2020 and 2019, there were 48,943,082 and 3,930,336 common stocks issued and outstanding. Warrants The Company sold warrants to purchase 9,075,000 shares of the Company's common stock in the public offering and the private placement on May 22, 2020. One warrant entitles the holder to purchase one whole share of common stock at a price of $11.50 per share. At December 31, 2020, there were 9,075,000 warrants outstanding which will become exercisable on May 22, 2021. Disgorgement of short swing profits For the year ended December 31, 2020, the Company recognized $432 increase to Additional Paid in Capital as a capital contribution from a stockholder for the disgorgement of short swing profits under Section 16 (b) of the Exchange Act, from B. Riley Securities, Inc, which is affiliated with B. Riley Financial Inc, a shareholder owning more than 5% of our common stock. The Company received the full payment in January 2021.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsOn January 22, 2021, the Triggering Event for the issuance of the Earnout Shares occurred as the Company's stock price exceeded $16.00 per share for 20 trading days within a consecutive 30-trading day period during the Earnout Period as described in Note 2. This Triggering Event resulted in the issuance of 2,000,000 shares of the Company's common stock. In addition, the Block B Sponsor Earnout Shares (as defined in Note 2) of 859,000 shares were released upon the achievement of the daily milestone of $16.00 per share as discussed in Note 2.

Nature of Operations and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe financial statements include the accounts of the Company and its 100% owned direct and indirect subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). All significant intercompany transactions and balances have been eliminated in the preparation of the consolidated financial statements.
Reclassification of Prior Year Presentation	Reclassification of Prior Year Presentation Certain prior year amounts have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the reported results of operations. Adjustment has been made to the Consolidated Balance sheets for the year ended December 31, 2019, to reclassify account payable and accrued expense to related parties and vendor deposits from prepaid and other current assets. These changes in classification also affected cash flows from operating activities for the year ended December 31, 2019 in the Consolidated Statements of Cash Flows.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash and highly liquid investments purchased with original maturities of three months or less.
Concentration of Credit Risk	Concentration of Credit Risk The Company maintains cash balances at FDIC-insured institutions. However, the FDIC limits may be exceeded at times. The Company has not experienced any losses on such accounts.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimates. The most significant estimates in the accompanying financial statements include the valuation of Contingently Issuable Common stock , derivatives, the relative fair value allocation of Phase II bridge financing proceeds, the valuation of inventory, and estimated lives used for depreciation and amortization purposes.
Income Taxes and Deferred Taxes	Income Taxes and Deferred Taxes The Company complies with the accounting and reporting requirements of FASB ASC Topic 740, Income Taxes (ASC 740). Income taxes are computed under the asset and liability method reflecting both current and deferred taxes, which reflect the tax impact of all events included in the financial statements. The balance sheet approach (i) reflects a current tax liability or asset recognized for estimated taxes payable or refundable on tax returns for the current and prior years, (ii) reflects a deferred tax liability or asset recognized for the estimated future tax effects attributable to temporary differences and carryforwards, (iii) measures current and deferred tax liabilities and assets using the enacted tax rate of which the effects of future changes in tax laws or rates are not anticipated, and (iv) reduces deferred tax assets, if necessary, by the amount of any tax benefits that, based on available evidence, are not expected to be realized. ASC 740 prescribes a recognition threshold and a measurement attribute for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. Eos recognizes deferred tax assets only to the extent that management concludes these assets are more-likely-than-not to be realized. Significant judgement is required in assessing and estimating the more-likely-than-not tax consequences of the events included in the financial statements. Management considers all available positive and negative evidence, including future reversals of existing temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations.The Company recognizes accrued interest and penalties related to unrecognized tax benefits, if any, as income tax expense. Eos records uncertain tax positions in accordance with ASC 740 on the basis of a two-step process in which (i) management determines whether it is more-likely-than-not that the tax position will be sustained on the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority.
Impairment of Long-Lived Assets	Impairment of Long — Lived AssetsThe Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. An assessment is performed to determine whether the depreciation and amortization of long-lived assets over their remaining lives can be recovered through projected undiscounted future cash flows. The amount of any long-lived asset impairment is measured based on fair value and is charged to operations in the period in which a long-lived assets impairment is determined by management.
Intangible Assets	Intangible Assets Intangible assets are stated at their historical cost and amortized on a straight-line basis over their expected useful lives.
Property and Equipment, net	Property and Equipment, net Equipment is stated at cost, less accumulated depreciation. Depreciation is computed on a straight-line basis over the estimate useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the improvements or the life of the lease. Maintenance and repair expenditures are expensed as incurred. Expenditures which significantly improve or extend the life of an asset are capitalized.
Revenue from Contracts with Customers/Royalty Revenue	Revenue from Contracts with Customers Revenue is earned from the sales, installation, and commissioning of energy storage systems and is derived from customer contracts. Revenue is recognized in an amount that reflects the consideration to which the Company expects to be entitled in exchange for transferring the promised goods and/or services to the customer, when or as the Company’s performance obligations are satisfied. For product sales of energy storage systems, the Company’s performance obligations are satisfied at the point in time when the customer obtains control of the system, which is either upon delivery of the goods at the customer’s designated location or upon the customer’s acceptance of the product after commissioning and testing at the customer’s site, depending on the specific terms of the respective contract with the customer. In addition, the corresponding installation and commissioning services related to the systems are performance obligations satisfied over time as the respective services are performed, based on an input measure of progress as labor costs relating to the installation and commissioning services are incurred. Further, extended warranties are offered by the Company and are identified as performance obligations that are satisfied over time, based on a time-lapsed measure of progress resulting in a ratable recognition of revenue over the respective warranty period. Payment terms generally include advance payments to reserve capacity and/or upon issuance of the customer’s purchase order, shipment readiness, with the remainder upon delivery and commissioning of the system. Shipping and handling costs are included in cost of sales. Sales tax collected from customers are recorded on a net basis and therefore, not included in revenue. Sales tax is recorded as a liability (payable) until remitted to governmental authorities. The Company may enter into sales contracts that provide for performance obligations in addition to the sale of the product, including performance guarantees and service obligations. Under these sales contracts, transaction price is allocated to the various performance obligations based on the relative stand-alone selling prices of the promised goods and services. When the stand-alone selling price is not observable, revenue is determined based on a best estimate of selling price using cost plus a reasonable margin and is recognized ratably over the period of performance. Determination of Transaction Price The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring products or services to the customer. The Company includes any fixed charges within its contracts as part of the total transaction price. In addition, several contracts include variable consideration such as refunds, penalties, and the customer’s right to return. The Company has concluded that its estimation of variable consideration results in an adjustment to the transaction price such that it is probable that a significant reversal of cumulative revenue would not occur in the future. Assessment of Estimates of Variable Consideration Many of the Company’s contracts with customers contain some component of variable consideration. The Company estimates variable consideration, such as refunds, penalties, and the customer’s right to return, using the expected value method, and adjusts transaction price for its estimate of variable consideration. Throughout the year, we update our estimate of variable consideration on a monthly basis, and adjust transaction price accordingly by recording an adjustment to net revenue and refund liability with respect to variable consideration such as penalties, refunds, and credits to customers. Therefore, management applies the constraint in its estimation of variable consideration for inclusion in the transaction price such that it is probable that a significant reversal of cumulative revenue would not occur in the future. Practical Expedients and Exemptions As permitted by ASC 606, the Company elected to use certain practical expedients in connection with the implementation of ASC 606. The Company treats costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset the Company would recognize is one year or less. The Company does not adjust the transaction price for significant financing components, as the Company’s contracts typically do not span more than a one year period. The election of these practical expedients results in accounting treatments that the Company believes are consistent with historical accounting policies and, therefore, these elections of practical expedients do not have a material impact on the comparability of the financial statements as no revenue was earned during the year ended December 31, 2020 and December 31, 2019. Royalty Revenue The Company receives sales-based royalty payments related to the licensing of intellectual property to the Company’s JV. The Company recognizes royalty revenues when the licensee sells products to third parties.
Product Warranty	Product Warranty Warranty obligations are incurred in connection with the sale of the Company’s products. The Company generally provides a standard warranty for a period of one to two years, commencing upon commissioning. Costs to provide for warranty obligations are estimated and recorded as a liability at the time of recording the sale. Extended warranties are identified as performance obligations in the Company’s contracts with customers, and are discussed as part of revenue from contracts with customers. Costs incurred in satisfying the Company’s performance obligations with respect to extended warranties are recognized as expense when incurred.
Government Grants	Government Grants The Company records grants received or receivable from government agencies as an offset to the related costs for which the grants are intended to compensate the Company. The costs of satisfying the Company’s obligations under the respective grant agreements are recognized as expense when incurred. Once the expenses are approved by the government agencies the Company records the grant receivable and related grant income. Grants received from government agencies for which expenses have not been incurred are included within accrued expenses.
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as incurred, which include materials, supplies, salaries, benefits and other costs related to research, development and testing of products.
Rent Expense	Rent Expense The Company records rent expense on a straight-line basis based on the total minimum lease payments over the term of the lease. Differences between cash paid for lease payments and rent expense are recorded as Deferred rent on the Balance Sheets.
Accounts Receivable	Accounts ReceivableThe Company evaluates the creditworthiness of its customers. If the collection of any specific receivable is doubtful, an allowance is recorded in the allowance for doubtful accounts.
Inventory	Inventory Inventories are stated at the lower of cost, which approximates cost determined on a first-in, first-out basis, or net realizable value. The Company records inventory when it takes delivery and title to the product according to the terms of each supply contract. The Company evaluates its ending inventories for excess quantities and obsolescence. Inventories that management considers excess or obsolete are reserved. Management considers forecasted demand in relation to the inventory on hand, competitiveness of product offerings, market conditions and product life cycles when determining excess and obsolescence and net realizable value adjustments. Once inventory is written down and a new cost basis is established, it is not written back up if demand increases.
Investment in unconsolidated joint venture	Investment in unconsolidated joint venture The Company accounts for its investment in its unconsolidated joint venture using the equity method of accounting as it has been determined that the Company has the ability to exercise significant influence and is not otherwise required to consolidate. All significant decisions require unanimous consent of both joint venture members. Under the equity method, the investment is initially recorded at cost and subsequently adjusted for the Company’s share of equity in the joint venture’s income or loss. The Company reviews its investments for other-than-temporary impairment whenever events or changes in business circumstances indicate that the carrying value of the investment may not be fully recoverable. Investments identified as having an indication of impairment are subject to further analysis to determine if the impairment is other than temporary and to estimate the investment’s fair value.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation is estimated at the grant date based on the fair value of the award and is recognized as expense over the requisite service period of the award. The Company uses the Black-Scholes option pricing model to estimate the fair value of awards, and generally these awards only have service conditions. The Company recognizes compensation cost on a straight-line basis over the requisite service period of the award, which is generally the award vesting term. For awards with performance conditions, we recognize compensation costs using an accelerated attribution method over the vesting period. Compensation costs are recognized only if it is probable that the performance condition will be satisfied. Determining the appropriate fair value model and related assumptions requires judgment, including estimating volatility of the Company’s common stock and expected terms. The expected volatility rates are estimated based on historical and implied volatilities of comparable publicly traded companies. The expected term represents the average time that the options that vest are expected to be outstanding based on the vesting provisions, which is determined through the simplified method, since the Company does not have sufficient historical experience regarding the exercise of options. The Company has elected to recognize forfeitures as incurred.
Earning (loss) Per Share	Earnings (loss) Per Share In accordance with the provisions of FASB ASC Topic 260, Earnings per Share, basic earnings per share (“EPS”) is computed by dividing earnings available to common shareholders by the weighted average number of shares of common stock outstanding during the period. Other potentially dilutive common shares, and the related impact to earnings, are considered when calculating EPS on a diluted basis. In computing diluted EPS, only potential common shares that are dilutive, those that reduce EPS or increase loss per share, are included. The effect of contingently issuable shares are not included if the result would be anti-dilutive, such as when a net loss is reported.
Segments	Segments The Company’s chief operating decision-maker (“CODM”) is its Chief Executive Officer and President. Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the CODM in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, the Company has determined that it operates in one operating and one reportable segment.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, and notes payable — related party and long term debt. Accounting standards establish a hierarchy which prioritizes the inputs to valuation techniques used to measure fair value into three levels. The fair value hierarchy gives the highest priority to quoted market prices (unadjusted) in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Accounting standards require financial assets and liabilities to be classified based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the fair value of assets and liabilities and their placement within the fair value hierarchy levels. The carrying value of cash and cash equivalents, accounts receivable, and accounts payable are considered to be representative of their fair value due to the short maturity of these instruments. The fair value of both the Company’s convertible notes payable — related party (the “Convertible Notes”) and the embedded derivative liability are classified within Level 3 of the fair value hierarchy. The Company’s outstanding long term debt are deemed to be at fair value as the interest rates on these debt obligations are materially consistent with prevailing rates. The Company estimated the original fair value of the Contingently Issuable Common Stock based on a Monte Carlo simulation option-pricing model considering stock price of the Company, a risk free rate of 0.41% and volatility of 60% utilizing a peer group based on a five year term. This estimate was initially recorded as a distribution to shareholders and was presented as Contingently Issuable Common Stock. Upon the occurrence of a Triggering Event, any issuable shares would be transferred from Contingently Issuable Common Stock to common stock and Additional paid-in capital accounts. Pursuant to the guidance under ASC 815, Derivatives and Hedging, the Sponsor Earnout Shares was classified as a Level 3 fair value measurement liability, and the increase or decrease in the fair value during the reporting period is recognized as expense or income accordingly. The fair values of the Sponsor Earnout Shares on the Closing date were estimated using a Monte Carlo simulation based on stock price of the Company, a risk free rate of 0.41% and volatility of 60% utilizing a peer group based on a five year term. The fair value of the first tranche of Sponsor Earnout Shares ("Block A") that vested on December 16, 2020 was based on the closing share price of the Company’s publicly traded stock on that date. The fair values of the second tranche of the Sponsor Earnout Shares ("Block B) on December 16, 2020, when the Block B shares were reclassified from liability to equity, were estimated using a Monte Carlo simulation based on stock price of the Company, a risk free rate of 0.36% and volatility of 60% utilizing a peer group based on a five- year term. The estimated future cash flows of the Convertible Notes were discounted using a discount rate derived from an appropriate risk-free interest rate yield curve and credit spread, and the estimated repayment date. As the Company does not have a market observable credit spread, the Company obtained a range of potential credit spreads available from market observable information on entities with a comparable credit risk. As of December 31, 2019, the estimated fair value of the convertible notes payable — related party is approximately $65,942, as compared to the carrying value of approximately $76,559. The fair value of the embedded derivatives are determined using valuation techniques that require the use of assumptions concerning the amount and timing of future cash flows, discount rates, probability of future events and redemption dates that are beyond management’s control.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Pursuant to the Jumpstart Our Business Startups Act (“ JOBS Act ”), an emerging growth company is provided the option to adopt new or revised accounting standards that may be issued by the FASB or the SEC either (i) within the same periods as those otherwise applicable to non-emerging growth companies or (ii) within the same time periods as private companies. The Company has elected to use the extended transition period for complying with any new or revised financial accounting standards. As a result, the Company’s financial statements may not be comparable to the financial statements of issuers who are required to comply with the effective date for new or revised accounting standards that are applicable to public companies. We also intend to continue to take advantage of some of the reduced regulatory and reporting requirements of emerging growth companies pursuant to the JOBS Act so long as we qualify as an emerging growth company. In February 2016, the FASB issued ASU 2016-02, Leases, which will amend current lease accounting to require lessees to recognize (i) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis, and (ii) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model. The Company is an emerging growth company and would not be required to adopt this ASU No. 2016-02 until January 1, 2022. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in ASU 2016-13 will provide more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2019, the FASB issued ASU No. 2019-10 (“ASU 2019-10”), which extends the effective date for adoption of ASU 2016-13 for certain entities. As a result of the provisions in ASU 2019-10, and as the Company was a smaller reporting company as of December 31, 2020, the Company will not be required to adopt ASU 2016-13 until January 1, 2023. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In December 2019, the FASB issued Accounting Standards Update No. 2019-12 – Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes, as part of its initiative to reduce complexity in the accounting standards. The amendments in ASU 2019-12 eliminate certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. This ASU is effective for public business entities for fiscal years and interim periods beginning after December 15, 2020. The adoption of this ASU does not have a material impact on the Company's consolidated financial statements.

Nature of Operations and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Antidilutive Shares Excluded from Calculation of Earnings Per Share

The following potentially dilutive shares were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented:


	For the year ended December 31
	2020	2019
Stock Options and Restricted Units	2,185,954	392,838
Warrants	9,075,000	—
Block B Sponsor Earnout Shares subject to restrictions	859,000	—
Contingently Issuable Common Stock	2,000,000	—
Convertible Notes (if converted)	—	7,655,908
Contingent redeemable preferred units	—	12,964,231

Merger Agreement and Reverse Recapitalization (Tables)

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Summary of Reverse Recapitalization

In accounting for the reverse recapitalization, the total cash proceeds amounted to $142,345 and resulted in the issuance of 18,364,805 shares of Common Stock, as shown in the table below (dollars in thousands, expect per share amounts).


	Total Shares	Available Cash
Balance, November 15, 2020	22,525,000	$	167,411
Less redemption of BMRG shares prior to the Merger	6,442,195	$	65,066
Less Sponsor Earnout Shares subject to restriction	1,718,000	$	—
Issuance of PIPE Shares	4,000,000	$	40,000
Balance issued upon Merger with BMRG	18,364,805	$	142,345

Revenue Recognition (Tables)

12 Months Ended

Dec. 31, 2020

Revenue from Contract with Customer [Abstract]

Information about Contract Liabilities from Contracts with Customers

The following table provides information about contract liabilities from contracts with customers:


	December 31, 2020		December 31, 2019		December 31, 2018
Contract liabilities	$	77	$	300	$	718

Revenue Expected to be Recognized for Unsatisfied Performance Obligation


December 31, 2020	2021		2022		2023		2024		Thereafter
Product Revenue	$	77	$	0	$	0	$	0	$	0

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Components of Property and Equipment, Net

As of December 31, 2020 and 2019, property and equipment, net consisted of the following:


	2020		2019		Useful lives
Equipment	$	7,055	$	5,910	5	—	10 years
Capital lease	201		201		5 years
Furniture	211		125		5	—	10 years
Leasehold Improvements	2,732		2,732		Lesser of useful life/remaining lease

Tooling	523		150		2	—	3 years
Total	10,722		9,118
Less: Accumulated Depreciation and Amortization	(5,069)		(3,802)
	$	5,653	$	5,316

Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Estimated Future Amortization Expense of Intangible Assets

Estimated future amortization expense of intangible assets as of December 31, 2020 are as follows:


2021	$	40
2022	40
2023	40
2024	40
2025	40
Thereafter	120
	$	320

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Future Minimum Lease Commitments for Operating Leases

Future minimum lease commitments as of December 31, 2020 are as follows:


	Operating		Capital
2021	$	685	$	14
2022	755		4
2023	825		—
2024	895		—
2025	966		—
Later years	679		—
Total minimum lease payments	$	4,805	$	18
Less amounts representing interest			3
Present value of minimum lease payments			$	15

Future Minimum Lease Commitments for Capital Leases

Future minimum lease commitments as of December 31, 2020 are as follows:


	Operating		Capital
2021	$	685	$	14
2022	755		4
2023	825		—
2024	895		—
2025	966		—
Later years	679		—
Total minimum lease payments	$	4,805	$	18
Less amounts representing interest			3
Present value of minimum lease payments			$	15

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Components of Income Tax Expense (Benefit)

Income tax expense (benefit) for the years ended December 31, 2020 and 2019 was as follows:


	2020		2019
Current expense (benefit):
U.S. federal	$	—	$	—
U.S. state and local	—		—
Total current income tax (benefit) provision	—		—
Deferred expense (benefit):
U.S. federal	$	—	$	—
U.S. state and local	—		—
Total deferred income tax (benefit) provision	—		—
Total income tax (benefit) provision	$	—	$	—

Reconciliation from Statutory U.S. Federal Income Tax Rate to Effective Tax Rate

The reconciliation from the statutory U.S. federal income tax rate to the effective tax rate is as follows:


	2020	2019
Income (loss) before income taxes	(68,754)	(79,483)
Statutory U.S. federal income tax (21%)	(14,439)	(16,691)
State and local income tax	(3,149)	1,548
Disallowed interest expense	4,564	11,903
Non-deductible transaction cost	66	—
Non-deductible equity cost	1,698	—
Federal R&D credit	3,660	(1,002)
Uncertain tax position	322	—
Valuation allowance	7,360	4,215
Other	(82)	27
Total income tax expense	—	—
Effective tax rate	—	—

Components of Deferred Tax Assets and Liabilities

The components of deferred tax assets and liabilities at December 31, 2020 and 2019 were as follows:


	2020		2019
Deferred tax assets:
NOL carryforwards	$	40,386	$	30,540
Tax credit carryforwards	1,204		4,346
Employee compensation	1,478		187
Accruals and reserves	1,743		543
Organizational costs	179		194
Transaction costs	324		—
Deferred tax assets, gross	$	45,314	35,810
Valuation allowance	(43,895)		(34,773)
Total deferred tax assets, net	$	1,419	$	1,037
Deferred tax liabilities:
Fixed assets	(1,358)		(1,010)
Investment in partnership	(61)		(27)
Deferred tax liabilities	(1,419)		(1,037)
Total deferred tax asset (liability)	—		—

Unrecognized Tax Benefits Associated with Uncertain Tax Positions

Eos has unrecognized tax benefits associated with uncertain tax positions as of December 31, 2020 and 2019 as follows:


	2020	2019
Gross unrecognized tax benefits as of January 1	—	—
Additions:
Current year tax positions	722
Prior year tax positions	—	—
Reduction of prior year tax positions	—	—
Settlements	—	—
Lapse of statute of limitations	—	—
Gross unrecognized tax benefits as of December 31	722	—

Convertible Notes Payable (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Summary of Balances Recognized upon Issuance of Convertible Notes

The following balances were recognized upon issuance of the Convertible Notes during the years ended December 31, 2020 and 2019:


	For the year ended December 31
	2019				2020
	Phase I		Phase II		Phase I		Phase II		Total
Convertible notes payable	$	40,587	$	35,973	$	510	$	31,793	$	108,863
Discount, original issuance	(20,946)		(23,982)		(340)		(21,196)		$	(66,464)
Premium (Discount), embedded derivative	181		(1,145)		—		(411)		$	(1,375)
Discount, fair value of preferred units	—		(2,031)		—		(1,759)		$	(3,790)
Discount, beneficial conversion features	(1,799)		—		—		—		$	(1,799)
Convertible notes payable, net	$	18,023	$	8,815	$	170	$	8,427	$	35,435

The balances attributable to the Convertible Notes immediately prior to the Merger were as follows:


	Phase 1		Phase 2		Pre-Merger balance
Convertible notes payable	$	41,097	$	67,766	$	108,863
Discount, original issuance	(21,286)		(45,178)		(66,464)
Discount, embedded derivative	181		(1,556)		(1,375)
Discount, fair value of preferred units	—		(3,790)		(3,790)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,904		50,524		73,428
Convertible notes payable, net	$	41,097	$	67,766	$	108,863

The balances attributable to the 2019 Convertible Notes on December 31, 2019 were as follows:


	Phase 1		Phase 2		December 31, 2019
Convertible notes payable	$	40,587	$	35,973	$	76,560
Discount, original issuance	(20,946)		(23,982)		(44,928)
Discount, embedded derivative	181		(1,145)		(964)
Discount, fair value of preferred units	—		(2,031)		(2,031)
Discount, beneficial conversion features	(1,799)		—		(1,799)
Discount, accumulated amortization	22,564		27,158		49,722
Convertible notes payable, net	$	40,587	$	35,973	$	76,560

Long-term Debt (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Summary of Long-term Indebtedness

The following is a summary of the Company’s long-term indebtedness (in thousands):


	December 31, 2020		December 31, 2019
Paycheck Protection Program loan payable	$	1,257	$	—
Other		94		—
Total		1,351		—
Less: long-term debt, current portion		(1,071)		—
Long-term debt	$	280	$	—

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Contingently Redeemable Preferred Units (Tables)

12 Months Ended

Dec. 31, 2020

Temporary Equity Disclosure [Abstract]

Activities Attributable to Preferred Units

During the years ended December 31, 2020 and 2019, activities attributable to the EES Preferred Units was as follows:


	Preferred Units
	Units	Amount
Balance, December 31, 2018	68,716	$	105,548
Contributions allocated to EES Preferred Units	11,991	2,031
Discount on convertible notes, beneficial conversion feature	—	1,786
Balance, December 31, 2019	80,707	109,365
Contributions allocated to EES Preferred Units	10,598	1,759
Issuance of EES Preferred Units	20,000	10,000
Balance, November 16, 2020	111,305	$	121,124

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Summary of Outstanding Stock Option Activity


	Shares	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (years)
Options Outstanding at December 31, 2018	303,028	$	26.20	2.8
Granted	254,882	$	9.54
Cancelled/Forfeited	(165,072)	$	27.24
Options Outstanding at December 31, 2019	392,838	$	15.09	5.4
Granted	1,972,679	$	9.07
Cancelled/Forfeited	(221,881)	$	18.57
Options Outstanding at December 31, 2020	2,143,636	$	9.19	9.5
Options Exercisable at December 31, 2020	15,859	$	26.81	1.7

Weighted-Average Assumptions Used to Determine the Fair Value of Options Granted

The weighted average assumptions used to determine the fair value of options granted in 2020 and 2019 are as follows:


	2020		2019
Volatility	52.99	%	58.20	%
Risk free interest rate	0.39	%	1.89	%
Expected life (years)	5.19		6.25
Dividend yield	0	%	0	%

Nature of Operations and Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 16, 2020	Nov. 16, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Uncertain tax position	$ 322	$ 0
Accounts receivable, net of allowances	35	0
Allowances for doubtful accounts	$ 35	0
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Fair value of embedded derivative liability		1,145
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of embedded derivative liability		1,681
Estimate of Fair Value Measurement \| Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes payable, related party		65,942
Reported Value Measurement \| Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes payable, related party		$ 76,559
Measurement Input, Risk Free Interest Rate \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of contingently issuable common stock, measurement Input				0.0041
Measurement Input, Price Volatility \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of contingently issuable common stock, measurement Input				0.60
Measurement Input, Expected Term \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of contingently issuable common stock, measurement Input				5
Block A Sponsor Earnout Shares \| Measurement Input, Risk Free Interest Rate \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input				0.0041
Block A Sponsor Earnout Shares \| Measurement Input, Price Volatility \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input				0.60
Block A Sponsor Earnout Shares \| Measurement Input, Expected Term \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input				5
Block B Sponsor Earnout Shares \| Measurement Input, Risk Free Interest Rate \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input			0.0036
Block B Sponsor Earnout Shares \| Measurement Input, Price Volatility \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input			0.60
Block B Sponsor Earnout Shares \| Measurement Input, Expected Term \| Valuation Technique, Option Pricing Model
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of Sponsor earnout shares, measurement input			5
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Standard product warranty term	1 year
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Standard product warranty term	2 years

Nature of Operations and Summary of Significant Accounting Policies - Antidilutive Shares Excluded from Calculation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock Options and Restricted Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,185,954	392,838
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	9,075,000	0
Block B Sponsor Earnout Shares subject to restrictions
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	859,000	0
Contingently Issuable Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,000,000	0
Convertible Notes (if converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	0	7,655,908
Contingent redeemable preferred units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	0	12,964,231

Merger Agreement and Reverse Recapitalization - Narrative (Details)
$ / shares in Units, $ in Thousands

12 Months Ended

Dec. 16, 2020

Nov. 16, 2020

USD ($)

tradingDay

$ / shares

Nov. 12, 2020

$ / shares

Dec. 31, 2020

USD ($)

Dec. 31, 2019

USD ($)

Nov. 15, 2020

USD ($)

$ / shares

Business Acquisition [Line Items]

Minimum threshold for closing cash pursuant to the Merger Agreement

$ 110,000

Aggregate purchase price set forth in the Merger Agreement

$ 300,000

Conversion price (in usd per share) | $ / shares

$ 10.00

Conversion ratio

0.0576

Contingent equity, earnout period

5 years

Contingent equity, earnout period, shares issued (in shares) | shares

2,000,000

Contingent equity, earnout period, threshold business days | tradingDay

Contingent equity, earnout period, threshold price (in usd per share) | $ / shares

$ 16.00

Contingent equity, earnout period, threshold trading days | tradingDay

Contingent equity, earnout period, threshold consecutive trading days | tradingDay

Original fair value of the contingently issuable shares

$ 17,944

Change in fair value, Sponsor Earnout Shares

$ 8,083

$ 0

Fair Value, Inputs, Level 3

Business Acquisition [Line Items]

Fair value measurement of Sponsor earnout shares

$ 16,235

Block A Sponsor Earnout Shares

Business Acquisition [Line Items]

Sponsor earnout shares subject to restriction (in shares) | shares

859,000

Contingent liability, earnout period

5 years

Contingent liability, earnout period, threshold price (in usd per share) | $ / shares

$ 12.00

Contingent liability, earnout period, threshold trading days | tradingDay

Contingent liability, earnout period, threshold consecutive trading days | tradingDay

Block A Sponsor Earnout Shares | Measurement Input, Risk Free Interest Rate | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

0.0041

Block A Sponsor Earnout Shares | Measurement Input, Price Volatility | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

0.60

Block A Sponsor Earnout Shares | Measurement Input, Expected Term | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

Block A Sponsor Earnout Shares | Common Stock

Business Acquisition [Line Items]

Release of Block A Sponsor earnout shares from restriction (in shares) | shares

859,000

^[1],[2]

Block B Sponsor Earnout Shares

Business Acquisition [Line Items]

Sponsor earnout shares subject to restriction (in shares) | shares

859,000

Contingent liability, earnout period

5 years

Contingent liability, earnout period, threshold price (in usd per share) | $ / shares

$ 16.00

Block B Sponsor Earnout Shares | Measurement Input, Risk Free Interest Rate | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

0.0036

Block B Sponsor Earnout Shares | Measurement Input, Price Volatility | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

0.60

Block B Sponsor Earnout Shares | Measurement Input, Expected Term | Valuation Technique, Option Pricing Model

Business Acquisition [Line Items]

Fair value of Sponsor earnout shares, measurement input

BMRG

Business Acquisition [Line Items]

Redemption of BMRG shares prior to the Merger (in shares) | shares

6,442,195

Redemption of BMRG shares prior to the Merger (in usd per share) | $ / shares

$ 10.10

Redemption of BMRG shares prior to the Merger

$ 65,066

Cash balance immediately prior to the Closing

$ 111,600

$ 167,411

Sponsor earnout shares subject to restriction (in shares) | shares

1,718,000

BMRG | Private Placement

Business Acquisition [Line Items]

Issuance of PIPE Shares (in shares) | shares

4,000,000

Issuance of PIPE Shares (in usd per share) | $ / shares

$ 10.00

Issuance of PIPE Shares

$ 40,000

[1]	See Note 1 for discussion of reverse capitalization given effect herein
[2]	See Note 2 for discussion of Sponsor Earnout Shares

Merger Agreement and Reverse Recapitalization - Summary of Reverse Recapitalization (Details) - USD ($)
$ in Thousands

12 Months Ended

Nov. 16, 2020

Nov. 12, 2020

Dec. 31, 2020

Dec. 31, 2019

Nov. 15, 2020

Business Acquisition [Line Items]

Common stock, shares outstanding (in shares)

48,943,082

3,930,336

Proceeds from capital infusion in reverse recapitalization

$ 142,345

$ 0

Common Stock

Business Acquisition [Line Items]

Net equity infusion from the Merger (in shares)

18,364,805

^[1]

BMRG

Business Acquisition [Line Items]

Common stock, shares outstanding (in shares)

22,525,000

Less redemption of BMRG shares prior to the Merger (in shares)

6,442,195

Less Sponsor earnout shares subject to restriction (in shares)

1,718,000

Cash

$ 111,600

$ 167,411

Less redemption of BMRG shares prior to the Merger

$ 65,066

BMRG | Private Placement

Business Acquisition [Line Items]

Issuance of PIPE Shares (in shares)

4,000,000

Issuance of PIPE Shares

$ 40,000

[1]	See Note 1 for discussion of reverse capitalization given effect herein

Revenue Recognition - Information about Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract liabilities	$ 77	$ 300	$ 718

Revenue Recognition - Narratives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Increase (decrease) in contract liabilities	$ (223)	$ (468)
Increase (decrease) in contract liabilities		(418)
Revenue recognized in contract liabilities	$ 184	$ 58

Revenue Recognition - Revenue Expected to be Recognized for Unsatisfied Performance Obligation (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 77
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 0
Revenue, remaining performance obligation, period

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory	$ 214	$ 0

Property and Equipment, Net - Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,722	$ 9,118
Less: Accumulated Depreciation and Amortization	(5,069)	(3,802)
Property and equipment, net	5,653	5,316
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,055	5,910
Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful lives	10 years
Capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 201	201
Useful lives	5 years
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 211	125
Furniture \| Minimum
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Furniture \| Maximum
Property, Plant and Equipment [Line Items]
Useful lives	10 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,732	2,732
Tooling
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 523	$ 150
Tooling \| Minimum
Property, Plant and Equipment [Line Items]
Useful lives	2 years
Tooling \| Maximum
Property, Plant and Equipment [Line Items]
Useful lives	3 years

Property and Equipment, Net - Narratives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 1,518	$ 2,083
Impairment loss charged	$ 0	$ 1,590

Intangible Assets - Narratives (Details) - Patents - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross patents value	$ 400
Patents useful lives	10 years
Patents amortization expenses	$ 40	$ 40

Intangible Assets - Estimated Future Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 40
2022	40
2023	40
2024	40
2025	40
Thereafter	120
Total	$ 320	$ 360

Investment in Unconsolidated Joint Venture (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019
Schedule of Equity Method Investments [Line Items]
Contribution made to the JV	$ 3,020	$ 768
Investment income (loss) from unconsolidated joint venture under the equity method of accounting	127	(178)
Investment in joint venture	$ 3,736	$ 589
Hi-Power
Schedule of Equity Method Investments [Line Items]
Initial estimated financial commitment			$ 4,100
Initial ownership interest			49.00%
Percentage of earning from equity method investment			5.00%

Commitment and Contingencies - Narratives (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($) customer	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 30, 2020 USD ($)	Apr. 26, 2017 ft²	Jun. 24, 2016 ft²
Operating Leased Assets [Line Items]
Additional number of square feet \| ft²					18,000	45,000
Annual cost escalations, percentage	10.00%	10.00%
Rent expense		$ 914	$ 930
Provision for firm purchase commitments	$ 1,585	1,585	0
Number of customers entered into loan commitment \| customer	1
Amount committed to lend	$ 1,000
Loan commitment on the consolidated balance sheet	100	100
Batteries
Operating Leased Assets [Line Items]
Non-cancellable purchase commitment	$ 2,504	2,504		$ 8,000
Purchases made		5,496
Cost of Sales
Operating Leased Assets [Line Items]
Rent expense		0	102
Research and Development Expense
Operating Leased Assets [Line Items]
Rent expense		713	430
General and Administrative Expense
Operating Leased Assets [Line Items]
Rent expense		$ 201	$ 398

Commitments and Contingencies - Future Minimum Lease Commitments (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Operating
2021	$ 685
2022	755
2023	825
2024	895
2025	966
Later years	679
Total minimum lease payments	4,805
Capital
2021	14
2022	4
2023	0
2024	0
2025	0
Later years	0
Total minimum lease payments	18
Less amounts representing interest	3
Present value of minimum lease payments	$ 15

Grant Expense, Net (Details) $ in Thousands	12 Months Ended
Grant Expense, Net (Details) $ in Thousands	Dec. 31, 2020 USD ($) grant	Dec. 31, 2019 USD ($)
Other Income and Expenses [Abstract]
Number of grants approved \| grant	2
Grants approval amount	$ 7,000
Grant expense (income), net	913	$ (469)
Grant income	381	984
Grant costs	1,294	515
Grant payments received	1,531	3,209
Deferred grant income	1,136	0
Grants receivable	$ 131	$ 326

Income Taxes - Narratives (Details) - USD ($)	12 Months Ended
Income Taxes - Narratives (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Net loss before income taxes for domestic operations	$ (68,754,000)	$ (79,483,000)
Tax provision (benefit)	0	0
Increase (decrease) in valuation allowance	(9,122,000)
Valuation allowance	43,895,000	34,773,000
Valuation allowance to be allocated to additional paid-in capital when released	1,762,000
Valuation allowance to be released through continuing operations	42,133,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
NOL carryforwards	174,258,000	137,909,000
NOL subject to expiration	89,051,000
NOL with an indefinite carryforward period	85,207,000
Domestic Tax Authority \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits (“R&D credit”)	4,603,000	3,733,000
Amount federal R&D credits will expire unused	4,530,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
NOL carryforwards	60,206,000
State and Local Jurisdiction \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits (“R&D credit”)	$ 1,131,000	$ 613,000

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current expense (benefit):
U.S. federal	$ 0	$ 0
U.S. state and local	0	0
Total current income tax (benefit) provision	0	0
Deferred expense (benefit):
U.S. federal	0	0
U.S. state and local	0	0
Total deferred income tax (benefit) provision	0	0
Total income tax (benefit) provision	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Reconciliation from Statutory to Effective Tax Rate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income (loss) before income taxes	$ (68,754,000)	$ (79,483,000)
Statutory U.S. federal income tax (21%)	(14,439,000)	(16,691,000)
State and local income tax	(3,149,000)	1,548,000
Disallowed interest expense	4,564,000	11,903,000
Non-deductible transaction cost	66,000	0
Non-deductible equity cost	1,698,000	0
Federal R&D credit	3,660,000	(1,002,000)
Uncertain tax position	322,000	0
Valuation allowance	7,360,000	4,215,000
Other	(82,000)	27,000
Total income tax (benefit) provision	$ 0	$ 0
Effective tax rate	0.00%	0.00%

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
NOL carryforwards	$ 40,386	$ 30,540
Tax credit carryforwards	1,204	4,346
Employee compensation	1,478	187
Accruals and reserves	1,743	543
Organizational costs	179	194
Transaction costs	324	0
Deferred tax assets, gross	45,314	35,810
Valuation allowance	(43,895)	(34,773)
Total deferred tax assets, net	1,419	1,037
Deferred tax liabilities:
Fixed assets	(1,358)	(1,010)
Investment in partnership	(61)	(27)
Deferred tax liabilities	(1,419)	(1,037)
Total deferred tax asset (liability)	$ 0	$ 0

Income Taxes - Unrecognized Tax Benefits Associated with Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Beginning balance	$ 0	$ 0
Additions of current year tax positions	722
Additions of prior year tax positions	0	0
Reduction of prior year tax positions	0	0
Settlements	0	0
Lapse of statute of limitations	0	0
Ending balance	$ 722	$ 0

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties	$ 2,517	$ 1,194
Director
Related Party Transaction [Line Items]
Costs incurred with related parties	69	19
Accounts payable and accrued expenses - related parties	0	73
Equity Method Investee \| Holtec International
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties	2,382	$ 1,121
Affiliated Entity \| Consultant Fees
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties	138
Affiliated Entity \| B.Riley Securities, Inc
Related Party Transaction [Line Items]
Due from related parties, current	432
Corporate Joint Venture \| Hi-Power
Related Party Transaction [Line Items]
Due from related parties, current	$ 278

Convertible Notes Payable - Narratives (Details)

4 Months Ended

7 Months Ended

12 Months Ended

Nov. 16, 2020

USD ($)

$ / shares

May 31, 2019

USD ($)

$ / shares

May 31, 2019

USD ($)

$ / shares

Dec. 31, 2019

USD ($)

$ / shares

Dec. 31, 2020

USD ($)

grant

Dec. 31, 2019

USD ($)

$ / shares

Nov. 15, 2020

USD ($)

Aug. 01, 2019

Jun. 01, 2019

Debt Instrument [Line Items]

Aggregate cash proceeds

$ 9,009,000

$ 19,346,000

Loss on extinguishment of convertible notes

(6,111,000)

Embedded derivative assets, initial fair value

$ 181,000

411,000

181,000

Embedded derivative liability, initial fair value

1,145,000

Embedded derivative liability

$ 1,681,000

1,681,000

Change in fair value, embedded derivative

2,092,000

(716,000)

Interest expense of convertible notes recognized

23,706,000

$ 49,708,000

Conversion of convertible notes payable (in shares) | shares

10,886,300,000

Conversion of convertible notes payable

$ 108,900,000

$ 108,863,000

Conversion price (in usd per share) | $ / shares

$ 10.00

Common Stock

Debt Instrument [Line Items]

Conversion of convertible notes payable (in shares) | shares

^[1]

10,886,336

Conversion of convertible notes payable

^[1]

$ 1,000

2019 Bridge Preferred Units

Debt Instrument [Line Items]

Issuance price of EES Preferred Units to the Holders (in usd per share) | $ / shares

$ 0.50

AltEnergy | Investor

Debt Instrument [Line Items]

Ownership percentage by AltEnergy

20.00%

14.00%

20.00%

Convertible Debt

Debt Instrument [Line Items]

Aggregate principal amount

$ 19,524,000

$ 5,469,000

$ 19,524,000

Number of phases | grant

Aggregate cash proceeds

$ 10,768,000

Discount, fair value of preferred units

$ 3,790,000

Convertible Debt | 2019 Phase I Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 13,529,000

Conversion ratio

1.15

Conversion price per unit (in usd per share) | $ / shares

$ 1.75

Liquidation ratio

1.5

3.0

2.0

Optional prepayment ratio

3.0

Aggregate gross equity proceeds threshold

$ 25,000,000

Percentage of holders for repayment to become due on demand

25.00%

Loss on extinguishment of convertible notes

$ 0

Redemption percentage

100.00%

Discount, fair value of preferred units

$ 0

Annual effective interest rates in excess

400.00%

Convertible Debt | 2019 Phase II Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 5,995,000

Conversion ratio

1.15

Conversion price per unit (in usd per share) | $ / shares

$ 0.50

Liquidation ratio

6.0

Aggregate cash proceeds

$ 11,991,000

Percentage of holders for repayment to become due on demand

25.00%

Redemption percentage

200.00%

Discount, fair value of preferred units

$ 2,031,000

Annual effective interest rates in excess

1200.00%

Convertible Debt | 2020 Phase II Notes

Debt Instrument [Line Items]

Liquidation ratio

6.0

Aggregate cash proceeds

10,598,000

Discount, fair value of preferred units

1,759,000

Convertible Debt | 2020 Phase I Notes

Debt Instrument [Line Items]

Aggregate cash proceeds

$ 170,000

Discount, fair value of preferred units

Convertible Debt | 2019 Convertible Notes

Debt Instrument [Line Items]

Discount, fair value of preferred units

$ 2,031,000

Debt instruments, coupon rate

0.00%

Convertible Debt | AltEnergy | 2019 Convertible Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 24,415,000

Convertible Debt | AltEnergy | Investor | 2019 Phase I Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 4,137,000

Convertible Debt | AltEnergy | Investor | 2019 Phase II Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 2,017,000

Convertible Debt | AltEnergy | Investor | 2020 Phase II Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 1,075,000

[1]	See Note 1 for discussion of reverse capitalization given effect herein

Convertible Notes Payable - Summary of Balances Recognized upon Issuance of Convertible Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Nov. 15, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Convertible notes payable, net	$ 1,351
Convertible Debt
Debt Instrument [Line Items]
Convertible notes payable		$ 108,863
Discount, original issuance		(66,464)
Premium (Discount), embedded derivative		(1,375)
Discount, fair value of preferred units		(3,790)
Discount, beneficial conversion features		(1,799)
Convertible notes payable, net, excluding gross discount		35,435
Discount, accumulated amortization		73,428
Convertible notes payable, net		108,863
Convertible Debt \| 2019 Phase I Notes
Debt Instrument [Line Items]
Convertible notes payable			$ 40,587
Discount, original issuance			(20,946)
Premium (Discount), embedded derivative			181
Discount, fair value of preferred units			0
Discount, beneficial conversion features			(1,799)
Convertible notes payable, net, excluding gross discount			18,023
Discount, accumulated amortization			22,564
Convertible notes payable, net			40,587
Convertible Debt \| 2019 Phase II Notes
Debt Instrument [Line Items]
Convertible notes payable			35,973
Discount, original issuance			(23,982)
Premium (Discount), embedded derivative			(1,145)
Discount, fair value of preferred units			(2,031)
Discount, beneficial conversion features			0
Convertible notes payable, net, excluding gross discount			8,815
Discount, accumulated amortization			27,158
Convertible notes payable, net			35,973
Convertible Debt \| 2020 Phase I Notes
Debt Instrument [Line Items]
Convertible notes payable		510
Discount, original issuance		(340)
Premium (Discount), embedded derivative		0
Discount, fair value of preferred units		0
Discount, beneficial conversion features		0
Convertible notes payable, net, excluding gross discount		170
Convertible Debt \| 2020 Phase II Notes
Debt Instrument [Line Items]
Convertible notes payable		31,793
Discount, original issuance		(21,196)
Premium (Discount), embedded derivative		(411)
Discount, fair value of preferred units	$ (1,759)	(1,759)
Discount, beneficial conversion features		0
Convertible notes payable, net, excluding gross discount		8,427
Convertible Debt \| Phase 1
Debt Instrument [Line Items]
Convertible notes payable		41,097
Discount, original issuance		(21,286)
Premium (Discount), embedded derivative		181
Discount, fair value of preferred units		0
Discount, beneficial conversion features		(1,799)
Discount, accumulated amortization		22,904
Convertible notes payable, net		41,097
Convertible Debt \| Phase 2
Debt Instrument [Line Items]
Convertible notes payable		67,766
Discount, original issuance		(45,178)
Premium (Discount), embedded derivative		(1,556)
Discount, fair value of preferred units		(3,790)
Discount, beneficial conversion features		0
Discount, accumulated amortization		50,524
Convertible notes payable, net		$ 67,766
Convertible Debt \| 2019 Convertible Notes
Debt Instrument [Line Items]
Convertible notes payable			76,560
Discount, original issuance			(44,928)
Premium (Discount), embedded derivative			(964)
Discount, fair value of preferred units			(2,031)
Discount, beneficial conversion features			(1,799)
Discount, accumulated amortization			49,722
Convertible notes payable, net			$ 76,560

Long-term Debt - Summary of Long-term Indebtedness (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt, including current portion	$ 1,351
Less: long-term debt, current portion	(1,071)	$ (76,559)
Long-term debt	280	$ 0
Loans Payable \| Paycheck Protection Program, CARES Act
Debt Instrument [Line Items]
Long-term debt, including current portion	1,257
Other
Debt Instrument [Line Items]
Long-term debt, including current portion	$ 94

Long-term Debt - Narratives (Details)	Apr. 07, 2020 USD ($)
Loans Payable \| Paycheck Protection Program, CARES Act
Debt Instrument [Line Items]
Amount received under the Paycheck Protection Program, CARES Act	$ 1,257,000

Contingently Redeemable Preferred Units - Narratives (Details)			11 Months Ended	12 Months Ended
	Nov. 16, 2020 shares	Dec. 31, 2019 USD ($) $ / shares shares	Nov. 16, 2020 USD ($) shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares
Temporary Equity [Line Items]
Debt threshold requiring Preferred Members majority vote \| $		$ 1,000,000,000			$ 1,000,000,000
Percentage deviated from approved budget requiring Preferred Members majority vote		15.00%			15.00%
Liquidation preference, percentage		8.00%			8.00%
Percentage threshold of voting units owned		50.00%			50.00%
Liquidation preference \| $		$ 136,816,000		$ 0	$ 136,816,000
Preferred units, conversion ratio (in shares)				1
Contributions allocated to EES Preferred Units (in shares) \| shares			10,598		11,991
Contributions allocated to EES Preferred Units \| $			$ 1,759,000		$ 2,031,000
Additional EES common units being issuable upon conversion (in shares) \| shares		144,200,000			144,200,000
EES common units to be issued upon conversion (in shares) \| shares		224,900,000
Unrecognized deemed dividend \| $		$ 0
Series C Preferred Units
Temporary Equity [Line Items]
Preferred units issued (in usd per share)		$ 1.10			$ 1.10
Conversion price per preferred unit (in usd per share)		1.10			1.10
Series D Preferred Units
Temporary Equity [Line Items]
Preferred units issued (in usd per share)		1.75			1.75
Conversion price per preferred unit (in usd per share)		1.75			1.75
2019 Bridge Preferred Units
Temporary Equity [Line Items]
Preferred units issued (in usd per share)		0.50			0.50
Issuance price of EES Preferred Units to the Holders (in usd per share)					$ 0.50
Contributions allocated to EES Preferred Units (in shares) \| shares					12,000,000
Contributions allocated to EES Preferred Units \| $					$ 2,031,000
EES Preferred Unit
Temporary Equity [Line Items]
Issuance price of EES Preferred Units to the Holders (in usd per share)					$ 0.50
Conversion price per preferred unit (in usd per share)		$ 0.50			$ 0.50
EES common units converted (in shares) \| shares	255,523,120
Common Stock
Temporary Equity [Line Items]
Conversion of contingently redeemable preferred units (in shares) \| shares	14,727,844

Contingently Redeemable Preferred Units - Activities Attributable to Preferred Units (Details) - USD ($) $ in Thousands	11 Months Ended	12 Months Ended
	Nov. 16, 2020	Dec. 31, 2019
Units
Beginning balance (in shares)	80,707	68,716
Contributions allocated to EES Preferred Units (in shares)	10,598	11,991
Issuance of EES Preferred Units (in shares)	20,000
Ending balance (in shares)	111,305	80,707
Amount
Beginning balance	$ 109,365	$ 105,548
Contributions allocated to EES Preferred Units	1,759	2,031
Discount on convertible notes, beneficial conversion feature		1,786
Issuance of EES Preferred Units	10,000
Ending balance	$ 121,124	$ 109,365

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Beginning outstanding balance (in shares)	392,838	303,028
Granted (in shares)	1,972,679	254,882
Cancelled/Forfeited (in shares)	(221,881)	(165,072)
Ending outstanding balance (in shares)	2,143,636	392,838	303,028
Exercisable (in shares)	15,859
Weighted-Average Exercise Price
Beginning outstanding balance (in usd per share)	$ 15.09	$ 26.20
Granted (in usd per share)	9.07	9.54
Cancelled/Forfeited (in usd per share)	18.57	27.24
Ending outstanding balance (in usd per share)	9.19	$ 15.09	$ 26.20
Exercisable (in usd per share)	$ 26.81
Weighted-Average Remaining Contractual Term (years)
Options outstanding	9 years 6 months	5 years 4 months 24 days	2 years 9 months 18 days
Options exercisable	1 year 8 months 12 days

Stock-Based Compensation - Narratives (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares remain for future issuance (in shares)	3,825,176	87,906
Shares issued to Restricted Units holders (in shares)	174,761,000	0
Stock compensation expense	$ 5,081	$ 135
Unrecognized stock compensation expense	7,416
Unrecognized stock compensation expense attributable to RUs	$ 6,944
Weighted average grant date fair value of options granted (in usd per share)	$ 5.38	$ 1.21
Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 4,104	$ 131
Period for unrecognized stock compensation expense to be recognized	4 years
Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting term	3 years
Options term	five
Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting term	5 years
Options term	ten years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RUs granted (in shares)	123,478,000	0
RUs outstanding and unvested (in shares)	42,318
RUs grant-date fair value (in usd per share)	$ 13.46
Stock compensation expense	$ 977	$ 4
Unrecognized stock compensation expense attributable to stock option	$ 472
Period for unrecognized stock compensation expense to be recognized	1 year
RSUs \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RUs outstanding and unvested (in shares)	31,188,000
RSUs \| Management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RUs outstanding and unvested (in shares)	11,130,000
2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	6,000,000

Stock-Based Compensation - Weighted-Average Assumptions Used to Determine the Fair Value of Options Granted (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Volatility	52.99%	58.20%
Risk free interest rate	0.39%	1.89%
Expected life (years)	5 years 2 months 8 days	6 years 3 months
Dividend yield	0.00%	0.00%

Shareholders' Equity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) vote $ / shares shares	May 22, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	1,000,000		1,000,000
Preferred stock, shares issued (in shares)	0		0
Preferred stock, shares outstanding (in shares)	0		0
Common stock, shares authorized (in shares)	200,000,000		200,000,000
Common stock, par value (in usd per share) \| $ / shares	$ 0.0001		$ 0.0001
Number of votes for each share \| vote	1
Common stock, shares issued (in shares)	48,943,082		3,930,336
Common stock, shares outstanding (in shares)	48,943,082		3,930,336
Common stock to be purchased through warrants (in shares)		9,075,000
Common stock to be purchased through each warrant (in shares)		1
Price of common stock to be purchased through warrants (in usd per share) \| $ / shares		$ 11.50
Warrant outstanding (in shares)	9,075,000
Capital contribution - disgorgement of short swing profits \| $	$ 432
Additional Paid in capital
Class of Stock [Line Items]
Capital contribution - disgorgement of short swing profits \| $	$ 432

Subsequent Events (Details) - $ / shares	Jan. 22, 2021	Dec. 31, 2020	Nov. 16, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Common stock, shares issued (in shares)		48,943,082		3,930,336
Block B Sponsor Earnout Shares
Subsequent Event [Line Items]
Contingent liability, earnout period, threshold price (in usd per share)			$ 16.00
Subsequent Event
Subsequent Event [Line Items]
Common stock, shares issued (in shares)	2,000,000
Subsequent Event \| Common Stock \| Block B Sponsor Earnout Shares
Subsequent Event [Line Items]
Release of Block A Sponsor earnout shares from restriction (in shares)	859,000