Eos Energy Enterprises (EOSE) 10-K 25 Feb 22 2021 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 16, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
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	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 715
Entity Common Stock, Shares Outstanding		53,958,013
Entity Central Index Key	0001805077
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
ICFR Auditor Attestation Flag	true
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

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Location	New York, NY
Auditor Firm ID	34

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 104,831	$ 121,853
Restricted cash	861	0
Accounts receivable, net	1,916	0
Inventory, net	12,976	214
Vendor deposits	16,653	2,390
Notes receivable, net	103	0
Prepaid expenses	2,595	2,274
Other current assets	2,637	636
Total current assets	142,572	127,367
Property and equipment, net	12,890	5,653
Intangible assets, net	280	320
Goodwill	4,331	0
Investment in joint venture	0	3,736
Security deposits, net	1,239	825
Notes receivable, long-term, net	3,547	100
Operating lease right-of-use asset, net	3,468	0
Other assets, net	848	263
Total assets	169,175	138,264
Current liabilities
Warranty accrual	12,531	3,378
Accrued expenses	7,674	5,093
Accounts payable and accrued expenses - related parties	1,200	2,517
Provision for firm purchase commitments - related parties	0	1,585
Operating lease liability, current portion	1,084	0
Notes payable, current portion	4,926	0
Long-term debt, current portion	1,644	924
Other current liabilities	858	88
Total current liabilities	29,917	13,585
Long-term liabilities
Operating lease liability, long-term	3,224	0
Notes payable	13,769	0
Long-term debt	4,727	427
Convertible notes payable - related party	84,148	0
Warrants liability - related party	926	2,701
Other liabilities	17	766
Total long-term liabilities	106,811	3,894
Total liabilities	136,728	17,479
COMMITMENTS AND CONTINGENCIES (NOTE 10)	0	0
SHAREHOLDERS' EQUITY
Common Stock, $0.0001 par value, 200,000,000 shares authorized, 53,786,632 and 48,943,082 shares outstanding at December 31, 2021 and 2020, respectively	5	5
Contingently Issuable Common Stock	0	17,600
Preferred stock, $0.0001 par value, 1,000,000 shares authorized, no shares outstanding at December 31, 2021 and 2020	0	0
Additional paid in capital	448,969	395,491
Accumulated deficit	(416,527)	(292,311)
Total shareholders' equity	32,447	120,785
Total liabilities and shareholders’ equity	$ 169,175	$ 138,264

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
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)	53,786,632	48,943,082
Common stock, shares outstanding (in shares)	53,786,632	48,943,082
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 OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue
Total revenue	$ 4,598	$ 219	$ 496
Costs and expenses
Cost of goods sold	46,494	5,509	8,332
Research and development expenses	19,193	13,593	11,755
Selling, general and administrative expenses	42,998	17,621	6,589
Loss on pre-existing agreement	30,368	1,262	1,121
Grant expense (income), net	269	913	(469)
Total costs and expenses	139,322	38,898	27,328
Operating loss	(134,724)	(38,679)	(26,832)
Other income (expense)
Interest income (expense), net	(604)	(115)	2
Interest expense – related party	(4,597)	(23,706)	(49,708)
Remeasurement of equity method investment	(7,480)	0	0
Loss on extinguishment of convertible notes - related party	1,273	0	(6,111)
Change in fair value, embedded derivative	17,507	2,092	(716)
Change in fair value, warrants liability - related party	1,775	(2,142)	0
Change in fair value, Sponsor Earnout Shares	0	(8,220)	0
Income (loss) from equity in unconsolidated joint venture	440	127	(178)
Gain on debt forgiveness	1,273	0	0
Sale of state tax attributes	2,194	0	4,060
Net loss	$ (124,216)	$ (70,643)	$ (79,483)
Basic and diluted loss per share attributable to common shareholders
Basic (in usd per share)	$ (2.36)	$ (7.51)	$ (20.22)
Diluted (in usd per share)	$ (2.36)	$ (7.51)	$ (20.22)
Weighted average shares of Common Stock
Basic (in shares)	52,664,349	9,408,841	3,930,336
Diluted (in shares)	52,664,349	9,408,841	3,930,336

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Block A Sponsor Earnout Shares	Block B Sponsor Earnout Shares	Common Stock	Common StockBlock A Sponsor Earnout Shares	Additional Paid in capital	Additional Paid in capitalBlock A Sponsor Earnout Shares	Additional Paid in capitalBlock B Sponsor Earnout Shares	Contingently Issuable Common Stock	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018				3,930,336
Beginning balance at Dec. 31, 2018	$ (104,374)			$ 0		$ 20,211			$ 0	$ (124,585)
Stock-based compensation	135					135
Net loss	(79,483)									(79,483)
Ending balance (in shares) at Dec. 31, 2019				3,930,336
Ending balance at Dec. 31, 2019	(183,722)			$ 0		20,346			0	(204,068)
Conversion of contingently redeemable preferred units (in shares)				14,727,844
Conversion of contingently redeemable preferred units	121,125			$ 2		121,123
Conversion of convertible notes payable (in shares)				10,886,336
Conversion of convertible notes payable	108,863			$ 1		108,862
Net equity infusion from the merger (in shares)				18,364,805
Net equity infusion from the Merger	125,682			$ 2		125,680
Contingently Issuable Common Stock	0								17,600	(17,600)
Transaction cost incurred in the Merger	(10,274)					(10,274)
Capital contribution - disgorgement of short swing profits	$ 432					$ 432
Shares issued to restricted units holders (in shares)	0			174,761		0
Stock-based compensation	$ 5,081					$ 5,081
Release of Block A sponsor earnout shares from restriction (in shares)					859,000
Release/Reclassification of sponsor earnout shares		$ 12,559	$ 11,682				$ 12,559	$ 11,682
Net loss	(70,643)									(70,643)
Ending balance (in shares) at Dec. 31, 2020				48,943,082
Ending balance at Dec. 31, 2020	120,785			$ 5		395,491			17,600	(292,311)
Stock-based compensation	$ 15,058					15,058
Release of Block A sponsor earnout shares from restriction (in shares)	0			859,000
Issuance of contingently issuable common stock (in shares)	0			1,999,185
Issuable Common Stock						17,600			(17,600)
Exercise of stock options (in shares)	123,837			123,837
Exercise of options	$ 1,074					1,074
Exercise of public warrants (in shares)				1,747,746
Exercise of warrants	$ 20,099					20,099
Stock issued during period (in shares)	0			154,600
Cancellation of shares used to settle payroll tax withholding (in shares)				(40,818)
Cancellation of shares used to settle payroll tax withholding	$ (353)					(353)
Net loss	(124,216)									(124,216)
Ending balance (in shares) at Dec. 31, 2021				53,786,632
Ending balance at Dec. 31, 2021	$ 32,447			$ 5		$ 448,969			$ 0	$ (416,527)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (124,216)	$ (70,643)	$ (79,483)
Adjustment to reconcile net loss to net cash used in operating activities
Stock-based compensation	15,058	5,081	135
Depreciation and amortization	2,613	1,558	2,123
Impairment of property and equipment	0	0	1,590
Non-cash lease expense	924	0	0
Remeasurement of equity method investment	7,480	0	0
Loss (Income) from equity in unconsolidated joint venture	(440)	(127)	178
Accreted interest on convertible notes payable – related party	1,545	23,706	49,708
Amortization of debt issuance cost	1,405	0	0
Gain (loss) on debt forgiveness	(1,273)	0	6,111
Change in fair value, embedded derivative	(17,507)	(2,092)	716
Change in fair value, warrants liability - related party	(1,775)	2,142	0
Change in fair value, Sponsor Earnout Shares	0	8,220	0
Other	2,950	31	(52)
Changes in operating assets and liabilities (net of assets and liabilities acquired)
Receivable on sale of state tax attributes	0	4,060	(4,060)
Prepaid expenses	(284)	(1,988)	(286)
Inventory	(10,096)	(214)	634
Accounts receivable	(1,916)	0	0
Vendor deposits	(7,419)	(593)	109
Security deposits	(414)	(17)	(64)
Accounts payable	5,823	(1,796)	(681)
Accrued expenses	2,581	3,115	(1,529)
Accounts payable and accrued expenses-related parties	(1,317)	1,323	1,140
Provision for firm purchase commitments	(5,475)	1,585	0
Operating lease liabilities	(846)	0	0
Notes payable	18,695	0	0
Other	(2,243)	90	(123)
Net cash used in operating activities	(116,147)	(26,559)	(23,834)
Cash flows from investing activities
Investment in notes receivable	(4,907)	0	0
Proceeds from notes receivable	1,320	0	0
Business acquisition, net of cash acquired	(160)	0	0
Investment in joint venture	(4,000)	(3,020)	(601)
Purchases of property and equipment	(15,589)	(3,605)	(2,299)
Net cash used in investing activities	(23,336)	(6,625)	(2,900)
Cash flows from financing activities
Principal payments on finance (capital) lease obligations	(11)
Principal payments on finance (capital) lease obligations		(15)	(72)
Proceeds from issuance of convertible notes payable – related party	100,000	9,009	19,346
Payment made for debt issuance cost	(4,370)	0	0
Proceeds from other financing	0	191	0
Repayment of other financing	(94)	(97)	(1,000)
Proceeds from Paycheck Protection Program loan	0	1,257	0
Proceeds attributable to beneficial conversion features of convertible notes payable – related party	0	0	1,793
Proceeds from equipment financing facility	7,000	0	0
Repayment of equipment financing facility	(455)	0	0
Proceeds from capital infusion in reverse recapitalization	0	142,345	0
Proceeds from exercise of stock options	1,074	0	0
Proceeds from exercise of public warrants	20,099	0	0
Repurchase of shares from employees for income tax withholding purposes	(353)	0	0
Transaction cost for the reverse recapitalization	0	(10,274)	0
Issuance of contingently redeemable preferred units	0	11,759	2,031
Other	432	0	0
Net cash provided by financing activities	123,322	154,175	22,098
Net increase (decrease) in cash, cash equivalents and restricted cash	(16,161)	120,991	(4,636)
Cash, cash equivalents and restricted cash, beginning of year	121,853	862	5,498
Cash, cash equivalents and restricted cash, end of year	105,692	121,853	862
Non-cash Investing and Financing Activities
Fixed assets acquired with finance lease	21	0	0
Right-of-use operating lease assets in exchange for lease liabilities	4,351	0	0
Contribution of inventory to joint venture	0	0	167
Accrued and unpaid capital expenditures	576	374	93
Issuance of convertible notes for interest paid-in-kind	2,900	0	0
Conversion of convertible notes to common stock in connection with merger	0	108,863	0
Conversion of contingently redeemable preferred stock to common stock in connection with merger	0	121,125	0
Receivable from disgorgement of short swing profits	0	432	0
Supplemental disclosures
Cash paid for interest	$ 157	$ 118	$ 6

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 104,831	$ 121,853
Restricted cash	861	0
Total cash, cash equivalents and restricted cash	$ 105,692	$ 121,853	$ 862	$ 5,498

Nature of Operations and Summar

Nature of Operations and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	Nature of Operations and Summary of Significant Accounting Policies Nature of Operations Eos Energy Enterprises, Inc. (f/k/a B. Riley Principal Merger Corp. II ("BMRG")) (the “Company” or "Eos") designs, develops, manufactures, and sells innovative energy storage solutions for electric utilities, and commercial and industrial (“C&I”) 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 focuses on developing and selling safe, reliable, long-lasting low-cost turn-key alternating current (“AC”) integrated systems using Eos’s direct current (“DC”) Battery System. The Company has a manufacturing facility in Turtle Creek, Pennsylvania to manufacture the DC Battery Systems integrated with the BMS for DC Battery Systems. The Company’s primary markets focus on integrating battery storage solutions with (1) solar systems that are connected to the utility power grid (2) solar systems that are not connected to the utility power grid (3) storage systems utilized to relieve congestion and (4) storage systems to assist C&I 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. Liquidity and Going Concern The Company is in the early commercialization stage of its lifecycle and, as such, has limited revenue generating activities. Accordingly, the Company has incurred significant recurring losses, and net operating cash outflows from operations since inception, which is attributable to its higher operating costs relative to its revenue base. Operating expenses consist primarily of costs related to the Company’s sales of their product along with the associated research and development costs, as well as other recurring general and administrative expenses. While management and the Company’s Board of Directors anticipate the Company will eventually reach a scale of profitability through the sale of battery energy systems and other complimentary products and services, the Company believes the current stage of the Company’s lifecycle justifies continued investment in the development and launch of products with outside capital at the expense of short-term profitability. Accordingly, we expect to continue to incur significant losses, and net operating cash outflows from operations for the foreseeable future to fund its obligations as they become due, which includes necessary funding to scale up the Company’s operations to allow for the delivery of order backlog and additional order opportunities for its battery systems, and continued investment in research and development. As of December 31, 2021, Eos had total assets of $169,175, which includes total cash and cash equivalents of $104,831, total liabilities of $136,728, which includes the total amounts owed on the Company’s outstanding convertible notes payable of $84,148 (see Note 15), notes payable of $13,769 and other long-term debt of $6,371 and a total accumulated deficit of $(416,527), which is primarily attributable to the significant recurring losses the Company has accumulated since inception. The Company has historically relied on outside capital to fund its cost structure and expects this reliance to continue for the foreseeable future until the Company reaches a scale of profitability through its planned revenue generating activities. However, as of the date of the accompanying financial statements were issued, management concluded that the Company did not have sufficient capital to support its current cost structure for one year after the date the accompanying financial statements were issued. Management believes these uncertainties raise substantial doubt about the Company’s ability to continue as a going concern. If the Company is unable to raise additional capital, the Company may have to significantly delay, scale back or discontinue the development or commercialization of its product. The Company has passed Part I of the application under the U.S. Department of Energy’s Loan Guarantee Solicitation for Applications for Renewable Energy Projects and Efficient Energy Projects (the “DOE Loan Program”). There can be no assurance that we will successfully complete Part II of the DOE Loan Program or otherwise be able to obtain this new funding, or any other new funding, on terms acceptable to us, on a timely basis, or at all. The accompanying consolidated financial statements have been prepared on the basis that we will continue to operate as a going-concern, which contemplates we will be able to realize assets and settle liabilities and commitments in the normal course of business for the foreseeable future. The accompanying financial statements do not include any adjustments that may result from the outcome of these uncertainties. 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 Principal 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 Combinations , 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 15 and Note 18 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. 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 consolidated financial statements include the warranty obligation, valuation of Contingently Issuable Common stock and Earnout shares, valuation of embedded derivatives, and fair value of consideration in business acquisition. Cash and Cash Equivalents Cash and cash equivalents include cash and highly liquid investments purchased with original maturities of three months or less. Restricted cash Restricted cash as of December 31, 2021 and December 31, 2020 was approximately $861 and $—, respectively, on the Company's consolidated balance sheets. All of the restricted cash on December 31, 2021 was held by the bank as collateral for the Company's corporate credit cards and subject to withdrawal restriction. 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. Accounts Receivable, net 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 credit losses. The Company had $1,925 and $35 of accounts receivable as of December 31, 2021 and 2020, with $9 and $35 of allowances for credit loss recorded, respectively. The total allowance for credit losses was included in Accounts Receivable, Net on the consolidated balance sheets. The activity in the allowance for credit losses was as follows: December 31, 2021 December 31, 2020 Beginning of Period $ 35 $ — Credit Loss Expense 9 35 Write-offs (35) — End of Period $ 9 $ 35 Inventory, net Inventories are stated at the lower of cost or net realizable value. Cost is computed using standard cost which approximates actual cost on a first-in, first-out basis. 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. A valuation allowance is recorded for inventories that management considers excess or obsolete. 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. 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. Business Combinations The Company accounts for the acquisition of a business using the acquisition method of accounting and allocates the purchase price of acquired entities to the underlying tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values, with any excess recorded as goodwill. The operating results of acquired businesses are included in the Company’s results of operations beginning as of their effective acquisition dates. Additional information regarding the business acquisition can be found in Note 3. Goodwill The Company accounts for goodwill as the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. Goodwill is not subject to amortization; rather, the Company tests goodwill for impairment annually or more frequently if an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of the asset below the carrying amount. The Company has the option to perform a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If this is the case, the quantitative assessment is required. If it is more likely than not that the fair value of the reporting unit is greater than its carrying amount, the quantitative goodwill impairment test is not required. In performing a qualitative assessment, the Company first assesses relevant factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a quantitative goodwill impairment test. The Company identifies and considers the significance of relevant key factors, events, and circumstances that could affect the fair value of the reporting unit. These factors include external factors such as macroeconomic, industry, and market conditions, as well as entity-specific factors, such as actual and planned financial performance. The Company completed the annual goodwill impairment test as of November 30, 2021, using a qualitative assessment for the reporting unit. The Company concluded that it is more likely than not that the fair value of the reporting unit is greater than the carrying amount, and a quantitative goodwill impairment test was not necessary. As a result of the annual assessment, there were no impairment charges for the year ended December 31, 2021. 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 upon shipment or delivery of the goods at the customer’s designated location and varies by contracts. In addition, the corresponding installation and commissioning services related to the systems are performance obligations satisfied over time as the respective services are performed. Further, extended warranties, maintenance and monitoring, and degradation guarantees 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 performance period. Transaction price is allocated to the various performance obligations based on the relative stand-alone selling prices of the promised goods and services. Stand-alone selling prices are either determined based on cost plus a reasonable margin or an adjusted market approach. 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 goods sold. 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. Assessment of Estimates of Variable Consideration and Determination of Transaction Price Many of the Company’s contracts with customers contain some component of variable consideration. The Company estimates variable consideration, such as refunds, penalties including liquidated damages, 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 estimates of variable consideration on a monthly basis and adjust the 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. 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. Practical Expedients and Exemptions As permitted by ASC 606, the Company elected to use certain practical expedients. The Company treats costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset recognized by the Company is one year or less. The election of the practical expedients results in accounting treatments that the Company believes are consistent with historical accounting policies and, therefore, the election of practical expedients does not have a material impact on the comparability of the financial statements. 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 two years and optional 20-year degradation guarantee, commencing upon commissioning. Costs to provide for warranty obligations are estimated and recorded as a liability at the time of recording the sale. Warranty reserves include management’s best estimate of the projected costs to repair or to replace any items under warranty, which is based on various factors, including the use of actual claim data to date, results of lab testing, factory quality data, field monitoring, and data on industry averages for similar products. Extended warranties and degradation guarantee 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. Leases Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to calculate the present value represents our incremental borrowing rate and is calculated based on the treasury yield curve that commensurate with the term of each lease, and a spread representative of our borrowing costs. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Leases may be classified as either operating leases or finance leases. We have made an accounting policy election to not include leases with an initial term of 12 months or less on the balance sheets. Prior to the adoption of ASC 842, Leases , the Company recorded 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 were recorded as Deferred rent, which is included in other liabilities on the balance sheets. See Note 21 for additional information. 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. 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. The Company 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. The Company 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 included in the net operating loss at December 31, 2021 and December 31, 2020 that do not meet the more-likely-than-not threshold under ASC 740 are $348 and $322, respectively. See Note 12 for further information. Earnings (loss) Per Share In accordance with the provisions of 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. See Note 23 for further information. 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 carrying amounts for the Company’s financial instruments classified as current assets and liabilities, including cash and cash equivalents, restricted cash, trade accounts receivable and accrued expenses and accounts payable, approximate fair value due to their short maturities. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 - Quoted prices in active markets for identical assets or liabilities. Level 2 - Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Refer to Note 22 for additional information. Recently Adopted Accounting Pronouncements Under the Jumpstart Our Business Startups (“JOBS”) Act, the Company qualified as an emerging growth company (“EGC”) and as such, elected not to opt out of the extended transition period for complying with new or revised accounting pronouncements. During the extended transition period, the Company was not subject to new or revised accounting standards applicable to public companies. Based on our public float calculation at June 30, 2021, the Company is deemed a Large Accelerated Filer under the U.S. Securities and Exchange Commission guidelines and ceased to qualify as an EGC effective December 31, 2021. The loss of EGC status resulted in losing the reporting exemptions noted above, and in particular requires our independent registered public accounting firm to provide an attestation report on the effectiveness of our internal control over financial reporting as of and for the year ended December 31, 2021 under Section 404(b) of the Sarbanes-Oxley Act and requires the adoption of ASU 2016-02 and ASU 2016-13 for the year ended December 31, 2021. On January 1, 2021, the Company adopted ASU 2016-02, Leases ("Topic 842"), using the transition method introduced by ASU 2018-11, which does not require revisions to comparative periods. Adoption of the new standard resulted in the recording of lease assets and lease liabilities of $3,662 and $4,465, respectively, as of January 1, 2021. The difference between the lease assets and lease liabilities primarily relates to deferred rent recorded in accordance with the previous leasing guidance. The new standard did not materially impact our consolidated statements of operations or statements of cash flows. On January 1, 2021, the Company adopted ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), and the subsequent amendments. The standard sets forth an expected credit loss model which requires the measurement of expected credit losses for financial instruments based on historical experience, current conditions and reasonable and supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost, and certain off-balance sheet credit exposures. The adoption of this standard did not have a material impact on our consolidated financial statements. On January 1, 2021, the Company adopted ASU No. 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) an

Merger Agreement and Reverse Re

Merger Agreement and Reverse Recapitalization	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
Merger Agreement and Reverse Recapitalization	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, except 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 20), 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 15 for further discussion of the convertible notes payable — related party and Note 18 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 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 55% 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. The Company estimated the original fair value of the contingently issuable shares to be $17,944, which remained 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 five 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 55% utilizing a peer group based on a five-year term. Sponsor Earnout Share was valued at $16,020 and recorded as a 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 consolidated 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 55% utilizing a peer group based on a five-year term. For the year ended December 31, 2020, $8,220 was recorded as loss from change in fair value of Sponsor Earnout Shares in our consolidated 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.

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Acquisition	Acquisition On April 8, 2021, the Company entered into a unit purchase agreement (the “Purchase Agreement”) with Holtec Power, Inc. (“Holtec”), in accordance with the terms and conditions of which the Company purchased from Holtec the remaining 51% percent interest in HI-POWER, LLC (“Hi-Power”) that was not already owned by the Company. Hi-Power was incorporated as a joint venture between the Company and Holtec in 2019 (refer to Note 8). In connection with the transaction, the Company also entered into a transition services agreement and a sublease with Holtec. The transaction closed on April 9, 2021 (“Acquisition Date”). Following the consummation of the transactions set forth in the Purchase Agreement (the “Transactions”), Hi-Power became a 100% indirect, wholly-owned subsidiary of the Company and the obligations of the parties under the Hi-Power joint venture terminated. The Purchase Agreement provides that the Company will pay an aggregate purchase price of $25,000 for 51% interest in Hi-Power, pursuant to the following schedule: $5,000 on each of May 31, 2021, May 31, 2022, May 31, 2023, May 31, 2024, and May 31, 2025, evidenced by a secured promissory note secured by the assets of the Company. The Purchase Agreement also requires that the Company pay to Holtec, on the closing of the Transactions, an amount in cash equal to $10,283. Payments to Holtec under this Purchase Agreement totaled $35,283. The fair value of these payments was $33,474 at the Acquisition Date and included $32,750 allocated to the termination of a pre-existing agreement with Holtec and $724 allocated to the acquisition. The obligations and rights of both parties under the pre-existing Joint Venture Agreement were terminated at the time of acquisition and $32,750 of the fair value of the consideration transferred was allocated to the termination of such agreement, which resulted in a loss on the pre-existing agreement of $30,368 for the year ended December 31, 2021. As of December 31, 2021, the Company had paid $10,283 on the date of closing and $5,000 notes payable due on May 31, 2021. The present value of the remaining payments was recorded as debt, which as of December 31, 2021 includes a current portion of $4,926 and a long-term portion of $13,769. Prior to the acquisition of the remaining 51% ownership interest in Hi-Power, we accounted for our initial 49% ownership interest in Hi-Power as an unconsolidated joint venture under the equity method of accounting (refer to Note 8). In connection with the acquisition of the remaining 51% ownership interest in Hi-Power, our consolidated financial statements now include all of the accounts of Hi-Power, and all intercompany balances and transactions have been eliminated in consolidation. The results of operations of Hi-Power have been included in the Company’s consolidated financial statements from the date of acquisition. The acquisition of Hi-Power did not have a material impact on the Company’s consolidated financial statements, and therefore historical and pro forma disclosures have not been presented. The consideration transferred for our now 100% ownership interest in connection with this acquisition, net of intercompany balances between the Company and Hi-Power, totaled $418, of which $205 represents the fair value of our previously held 49% ownership interest in Hi-Power. In accordance with ASC Topic 805-10-25-10, we remeasured our previously held 49% ownership interest in Hi-Power at its acquisition date fair value. As of the acquisition date, a loss of $7,480 was recognized in earnings for the remeasurement of our previously held 49% ownership interest. The following table summarizes the fair values of the assets acquired and liabilities assumed as of the Acquisition Date: Amount Inventory $ 2,666 Vendor deposits 818 Property and equipment, net 74 Goodwill 4,331 Accounts payable and accrued expenses (3,634) Provision for firm purchase commitments (3,890) Net assets acquired, net of cash and cash equivalents of $53 2 $ 365 The purchase price allocation and the measurement for acquisition consideration are based on management’s best estimates and assumptions as of the reporting date and are considered preliminary. The provisional measurements of identifiable assets and liabilities, and the resulting goodwill related to these acquisitions are subject to change and the final purchase price accounting could be different from the amounts presented herein. We expect to finalize the valuation as soon as practicable, but not later than one year from the acquisition date. The Company expects the goodwill recognized as part of the acquisition will be deductible for U.S. income tax purposes. The Company also incurred insignificant non-consideration acquisition expenses including legal and accounting services related to the acquisition, which are recorded in selling, general and administrative expenses on the Company’s consolidated statements of operations.

Revenue Recognition

Revenue Recognition	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition The Company primarily earns revenue from sales of its energy storage systems and services including installation and commissioning, as well as extended warranty services. Product revenues, which were recognized at a point in time, were $4,562, $184 and $496 for the years ended December 31, 2021, 2020 and 2019, respectively and service revenues, which were recognized over time, were $36, $35 and $— for the years ended December 31, 2021, 2020 and 2019, respectively. For the year ended December 31, 2021, we had two customers who accounted for 36.8% and 21.4% of the total revenue, respectively. For the year ended December 31, 2020, we only had two customers, who accounted for 84.1% and 15.9% of our revenue. For the year ended December 31, 2019, we had three customers who accounted for 36.3%, 31.4% and 26.1% of the total revenue. Contract Balances The following table provides information about contract assets and contract liabilities from contracts with customers, which are included in other current assets and other current liabilities on the consolidated balance sheets, respectively. December 31, December 31, Contract assets $ 1,369 $ — Contract liabilities $ 849 $ 77 The Company recognizes contract assets resulting from the timing of revenue recognition and invoicing. Contract liabilities primarily relate to advance consideration received from customers in advance of the Company satisfying performance obligations under contractual arrangements. 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. Contract assets increased by $1,369 during the year ended December 31, 2021. Contract liabilities increased by $772 during the year ended December 31, 2021. The Company recognized $77 of revenue during the year ended December 31, 2021 that was included in the contract liability balance at the beginning of the period. Contract liabilities decreased by $223 during the year ended December 31, 2020. The Company recognized $184 and $58 of revenue during the years ended December 31, 2020 and 2019 that was included in the contract liability balance at the beginning of the period, respectively. Transaction Price Allocated to Remaining Performance Obligations Contract liabilities of $849 as of December 31, 2021 are expected to be recognized within the next twelve months.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2021
Inventory Disclosure [Abstract]
Inventory	Inventory The following table provides information about inventory balances: December 31, 2021 December 31, 2020 Raw materials $ 11,898 $ — Work-in-process 43 — Finished goods 1,035 214 Total Inventory, net $ 12,976 $ 214

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net As of December 31, 2021 and 2020, property and equipment, net consisted of the following: 2021 2020 Useful lives Equipment $ 13,489 $ 7,055 5 — 10 years Finance lease 226 201 5 years Furniture 808 211 5 — 10 years Leasehold Improvements 2,933 2,732 Lesser of useful life/remaining lease Tooling 3,053 523 2 — 3 years Total 20,509 10,722 Less: Accumulated Depreciation and Amortization (7,619) (5,069) $ 12,890 $ 5,653 Depreciation and amortization expense related to property and equipment was $2,573, $1,518 and $2,083, during the years ended December 31, 2021, 2020 and 2019, respectively. For the years ended December 31, 2021, 2020, and 2019, impairment loss charged to the consolidated statements of operations was $—, $—, and $1,590, respectively, primarily related to obsolete equipment relating to the prior generation battery. These expenses are reflected in cost of goods sold, research and development expenses and selling, general and administrative expenses in the consolidated statements of operations.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	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, 2021, 2020, and 2019, the Company recorded amortization expenses of $40, $40, and $40 respectively, related to patents. Estimated future amortization expense of intangible assets as of December 31, 2021 are as follows: 2022 $ 40 2023 40 2024 40 2025 40 2026 40 Thereafter 80 $ 280

Investment in Unconsolidated Jo

Investment in Unconsolidated Joint Venture	12 Months Ended
	Dec. 31, 2021
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 was in Turtle Creek, Pennsylvania. The Company’s financial commitment was $4,100 in the form of a combination of cash and special purpose manufacturing equipment. Eos’s initial ownership interest was 49%. Both the Company and Holtec sell the products manufactured by Hi-Power. On April 9, 2021, the Company acquired the remaining 51% ownership interest and Hi-Power became a wholly-owned subsidiary thereafter. Refer to Note 3 for the acquisition details. The joint venture commenced manufacturing activities in the fourth quarter of 2020. For the years ended December 31, 2021, 2020, and 2019, contributions made to the JV were $4,000, $3,020, and $768, respectively. The investment income (loss) recognized from the unconsolidated joint venture under the equity method of accounting was $440, $127, and $(178) for the years ended December 31, 2021, 2020, and 2019, respectively. Our investment in the unconsolidated joint venture as of December 31, 2021 and 2020 was $— and $3,736, respectively.

Notes Receivable, net and Varia

Notes Receivable, net and Variable interest entities (“VIEs”) Consideration	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Notes Receivable, net and Variable interest entities (“VIEs”) Consideration	Notes Receivable, net and Variable interest entities (“VIEs”) Consideration Notes receivable consist primarily of amounts due to us related to the financing we offered to customers. We report notes receivable at the principal balance outstanding less an allowance for losses. We monitor the financial condition of the notes receivable and record provisions for estimated credit losses based on the credit quality of the borrowers, current conditions as well as other reasonable and supportable forecasts about the future. We charge interest at a fixed rate and interest income is calculated by applying the effective rate to the outstanding principal balance. The Company had notes receivable of $3,650 and $100 outstanding as of December 31, 2021 and 2020, respectively. Current expected credit loss was estimated for notes receivable under ASU No. 2016-13, Financial Instruments-Credit Losses. As of December 31, 2021 and 2020, the Company recorded an allowance for notes receivable of $6 and $—, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Firm Purchase Commitments To ensure adequate and timely supply of raw material for production, the Company, from time to time, enters into non-cancellable purchase contracts with vendors. At the end of each reporting period, the Company evaluates its non-cancellable firm purchase commitments and records a loss, if any, using the lower of cost or market approach used for inventory obsolescence. 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 net realizable value of the inventory is less than the cost. As of December 31, 2021, the Company had open purchase commitments of $5,370 under these contracts. Lease commitments The Company has lease commitments under lease agreements. Refer to Note 21 for discussion. Probable legal proceeding

Grant Expense, Net

Grant Expense, Net	12 Months Ended
	Dec. 31, 2021
Other Income and Expenses [Abstract]
Grant Expense, Net	Grant Expense, Net The Company was approved for two grants by the California Energy Commission (CEC) totaling approximately $7,000. In accordance with the grant agreements, we are 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 by the Company. During the years ended December 31, 2021, 2020, and 2019, we recorded grant expense (income), net of $269, $913, and ($469), which comprised of grant income of $2,025, $381, and $984 and grant costs of $2,294, $1,294, and $515, respectively. For the years ended December 31, 2021, 2020, and 2019, the Company received payments totaling $— , $1,531 and $3,209, respectively. As of December 31, 2021 and 2020, the Company had $— and $1,136 deferred grant income, respectively, which was recorded in accrued expense on the consolidated balance sheets, as well as a grant receivable, which was included in other current assets on the consolidated balance sheets, in the amount of $1,020 and $131, respectively. The expenses incurred by the Company related to the performance of studies in accordance with the respective grant agreements are offset, against the grants revenue received or receivable from the CEC for which the grant is intended to compensate the Company.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company 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 losses before income taxes for domestic operations for the years ended December 31, 2021, 2020, and 2019 were $(124,216), $(70,643), and $(79,483) respectively. Income expense (benefit) Income tax expense (benefit) for the years ended December 31, 2021, 2020, and 2019 was as follows: 2021 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 $ — $ — $ — The Company has no tax provision (benefit) for the periods ended December 31, 2021, 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: 2021 2020 2019 Income (loss) before income taxes $ (124,216) (70,643) $ (79,483) Statutory U.S. federal income tax (21%) (26,085) (14,835) (16,691) State and local income tax (6,592) (3,123) 1,548 Non-deductible convertible debt (3,676) 4,563 11,903 Non-deductible transaction cost — 66 — Non-deductible equity cost — 1,726 — Non-deductible warrant cost (373) 450 — Federal R&D Credit — 3,660 (1,002) Uncertain Tax Position — 322 — Valuation Allowance 36,541 7,253 4,215 Other 185 (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 non-deductible convertible debt. On September 8, 2021, the Small Business Administration authorized full forgiveness of $1,273 to the Company for the Paycheck Protection Program (PPP) Loan under the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”). For tax purposes, this amount is excludable in taxable income and included in “Other” in the reconciliation above. Deferred Income Taxes The Company 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, 2021 and 2020 were as follows: 2021 2020 Deferred tax assets: NOL carryforwards $ 63,203 $ 40,278 Capital loss carryforwards 710 — Tax credit carryforwards 65 1,204 Goodwill 8,471 — Employee compensation 4,455 1,478 Accruals and reserves 1,586 1,744 Organizational costs 162 179 Lease Liability 1,185 — Interest Limitation 1,430 — Inventory 1,448 — Transaction costs 301 324 Deferred tax assets, gross $ 83,016 $ 45,207 Valuation allowance (80,415) (43,788) Total deferred tax assets, net $ 2,601 $ 1,419 Deferred tax liabilities: Fixed assets (1,073) (1,358) Investment in partnership — (61) Right of Use Asset (954) — Note payable (497) — Intangibles (77) — Deferred tax liabilities (2,601) (1,419) Total deferred tax asset (liability) $ — $ — The Company’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, 2021 and 2020. During 2021, 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 2017 through 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. The Company anticipates participating in the program for the tax year 2020, but as of the balance sheet date, no 2020 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 the Company will not be able to utilize its deferred tax assets at December 31, 2021 and 2020 due to a history of cumulative losses. As such, the Company has a valuation allowance against its net deferred tax assets. The valuation allowance increased by $36,627 between December 31, 2021 and 2020. The increase was primarily attributable to an increase in NOL carryforwards and tax deductible goodwill in excess of financial statement goodwill. At December 31, 2021, the valuation allowance is $80,415, of which $1,762 will be allocated to additional paid-in capital when released. The remaining valuation allowance of $78,653 will be released through continuing operations. On April 8, 2021, the Company entered into a unit purchase agreement with Holtec Power Inc. in which the Company purchased the remaining 51% interest in HI-POWER, LLC that was not already owned by the Company. Please refer to Note 3 for additional background on the acquisition. For U.S. tax purposes, the Company will recognize amortizable goodwill in the amount of $36,768 equal to the excess in consideration paid over the fair value of the acquisition. Net Operating Losses & Tax Credits As of December 31, 2021 and 2020, the Company has federal research and development tax credits (“R&D credit”) of approximately $3,733 and $4,603, which begin to expire in varying amounts from 2031 – 2038 and 2031 – 2040, respectively, subject to the annual limitation described below. In addition, the Company has state R&D credits of approximately $65 for the year ended December 31, 2021, which will expire in 2024, and $1,131 for the year ended December 31, 2020, which will expire in varying amounts between 2022 and 2026. 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, 2021 and 2020, the Company has gross federal NOL carryforwards of approximately $263,270 and $173,868. As of December 31, 2021, the Company has state NOL carryforwards of $125,855. Regarding the federal NOL for the year ended December 31, 2021, $89,051 begins to expire in varying amounts from 2032 through 2036, while $174,219 has an indefinite carryforward period. The state NOL carryforwards begin to expire in varying amounts from 2039 through 2041. 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 as of December 31, 2021 and December 31, 2020, $3,733 and $4,603, respectively, of federal R&D credits will expire unused. As such, these credits have been written off as of December 31, 2021 and 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 the Company 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 the Company’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. The Company has unrecognized tax benefits associated with uncertain tax positions as of December 31, 2021, 2020, and 2019 as follows: 2021 2020 2019 Gross unrecognized tax benefits as of January 1 $ 722 $ — $ — Additions: Current year tax positions — 722 — Prior year tax positions — — — Rate change (3) — — Settlements — — — Lapse of statute of limitations — — — Gross unrecognized tax benefits as of December 31 $ 719 $ 722 $ — The total amount of gross unrecognized tax benefits was $719, $722 and $— for the year ended December 31, 2021, 2020 and 2019, respectively. The decrease in gross unrecognized tax benefits in 2021 was due to a change in state deferred tax rate Included in the balance of unrecognized tax benefits at December 31, 2021 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 2018 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. The Company 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, Income Taxes . 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.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related party transactions	Related Party Transactions Convertible Notes During the year ended December 31, 2021, the Company issued $100,000 aggregate principal amount of convertible notes to Spring Creek Capital, LLC, a wholly-owned, indirect subsidiary of Koch Industries, Inc (the “2021 Convertible Notes” or the “Notes”). In connection with the 2021 Convertible Notes, the Company paid $3,000 to B. Riley Securities, Inc., a related party, who acted as a placement agent. During the year ended December 31, 2021, the Company intends to repay the contractual interest due on December 30, 2021 in-kind as an increase to the principal amount. $2,900 of interest from the 2021 Convertible Notes was recorded as convertible notes - related party on the consolidated balance sheets. Refer to Note 15 for more information. During the years ended December 31, 2020 and 2019, the Company issued convertible notes payable (the “Legacy Convertible Notes”) to certain members. Refer to Note 15 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 were included in selling, general and administrative expenses in the consolidated statements of operations. Accounts Payable and Accrued Expenses - Related Parties Accounts payable and accrued expenses - related parties as of December 31, 2020 contains $138 consultant fee payable to an affiliate. Additionally, amount payable to Holtec under the Joint Venture agreement was $2,382 as of December 31, 2020, which was paid off in connection with the acquisition of Hi-Power. During the years ended December 31, 2021, 2020, and 2019, $30,368, $1,262, and $1,121 was charged to loss on pre-existing agreement, respectively. Refer to Note 3 for the acquisition details. 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 under Section 16 (b) of the Exchange Act, which was included in Other current assets. This amount was recognized as an increase to Additional Paid in Capital as capital contribution from stockholder. The Company received the full payment in January 2021. Vendor deposits As of December 31, 2020, vendor deposits included a balance of $278 deposits made to Hi-Power. Provision for firm purchase commitments As of December 31, 2020, the Company recorded a provision for firm purchase commitments with Hi-Power of $1,585. The related expense has been included as a component of cost of goods sold in the consolidated statements of operations. Warrants liability The Company has private warrants issued to affiliated company owned by B. Riley Securities, Inc. as of December 31, 2021 and 2020. Refer to Note 19 for details. Settlement Agreement As disclosed at the time of the Merger Agreement, prior to the execution and delivery of the Merger Agreement, certain unitholders of EES (“Hellman parties”) asserted claims (“Threatened Claims”) against another director and affiliated investors, including AltEnergy Storage VI, LLC (the "Securityholder Representative"), questioning the dilutive effect of certain historical security issuance on the former EES common unitholders. Under the Merger Agreement, the Securityholder Representative had the obligation and duty to vigorously defend against the Threatened Claims, and the Company had the obligation to advance or cause to be advanced to the Securityholder Representative up to $5,000 of defense costs, subject to a deductible of $2,000 (the "Deductible"), in connection with the investigation, defense, or settlement of any Threatened Claims. The Deductible was to be borne by the company, and any additional amounts advanced were reimbursable by the former unitholders of EES. On December 1, 2021, a Settlement Agreement was entered into between Hellman Parties and the Securityholder Representative pursuant to which, 300,000 Eos Shares (“Settlement Shares”) would be transferred to the Hellman parties from the EES unitholders at the time of merger. On December 28, 2021, the independent members of the Board approved a contribution of $1,200 towards the Settlement. Such determination was based on the independent members of the Board’s business judgment that, among other reasons, such a contribution (i) would ensure that the Company would not have to spend the entire $2,000 Deductible towards the costs of defense of any litigation, (ii) would avoid the additional cost, distraction, uncertainty, and overhang of litigation relating to the Mergers, (iii) would benefit the Company’s future relationships with its long-term investors, and (iv) would generate future goodwill with such investors during an important growth stage of the Company. As the Company’s contribution benefits certain Eos shareholders at the time of the Merger Agreement, including AltEnergy LLC and B. Riley Financial Inc, who are considered as related parties owning more than 5% of the equity interest in the Company, this transaction is considered a related party transaction. On December 29, 2021, an amendment to the Settlement Agreement between the Hellman Parties and the Securityholder Representative was entered into, pursuant to which, $1,200 of the value represented by the Settlement Shares was to be paid in cash, representing the equivalent of 140,023 of the Settlement Shares. The Company accrued $1,200 in accounts payable and accrued expenses - related party on December 31, 2021, which has been paid on January 4, 2022. The remaining 159,977 in Settlement Shares were transferred to the Hellman parties from the former EES unitholders, on a pro rata basis, on December 29, 2021.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses As of December 31, 2021 and 2020, accrued expenses consisted of the following: December 31, 2021 December 31, 2020 Accrued payroll $ 3,069 $ 2,146 Warranty accrual 2,112 — Accrued legal and professional fees 826 1,023 Other 1,667 1,924 Total $ 7,674 $ 5,093 The following table summarizes product warranty activity for the year ended December 31, 2021. December 31, 2021 Accrued warranty - beginning of period $ — Additions for current year deliveries 2,343 Warranty costs incurred (231) Accrued warranty - end of period $ 2,112

Convertible Notes Payable

Convertible Notes Payable	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Convertible Notes Payable	Convertible Notes Payable 2021 Convertible Notes On July 6, 2021, the Company entered into an investment agreement (the “Investment Agreement”) with Spring Creek Capital, LLC, a wholly-owned, indirect subsidiary of Koch relating to the issuance and sale to Koch of the 2021 Convertible Notes in the aggregate principal amount of $100,000. The transactions contemplated by the Investment Agreement closed on July 7, 2021 (the “Issue Date”). The Maturity Date of the 2021 Convertible Notes is June 30, 2026, subject to earlier conversion, redemption, or repurchase. Right after the issuance, Koch beneficially owned approximately 14% of the Company’s outstanding common stock. The 2021 Convertible Notes are senior unsecured obligations of the Company and rank equal in right of payment to all senior unsecured indebtedness of the Company, and will rank senior in right of payment to any indebtedness that is contractually subordinated to the 2021 Convertible Notes. Contractual Interest Rates - The 2021 Convertible Notes were issued at par and bear interest at a rate of 5% per year if interest is paid in cash, or, if interest is paid in-kind as an increase in the principal amount, at a rate of 6% per year. Interest on the 2021 Convertible Notes is payable semi-annually in arrears on June 30 and December 30. The Company, at its option, is permitted to settle each semi-annual interest payment in cash, in-kind, or any combination thereof. Conversion Rights - The 2021 Convertible Notes are convertible at the option of the Holder at any time prior to the maturity date at an initial conversion rate of 49.9910 shares of the Company’s common stock per $1,000 of capitalized principal (the “Holder’s Conversion Rights”). The effective conversion price is approximately $20.00 per share. The conversion rate is subject to adjustment upon the occurrence of certain dilutive events such as stock splits and combinations, stock dividends, mergers and spin-off. For the year ended December 31, 2021, there were no adjustments to conversion rate. As of December 31, 2021, 5,144,074 shares of the Company’s common stock were issuable upon conversion of the 2021 Convertible Notes including the principal and interest payment in-kind. The Company has the right to settle conversions in shares of common stock, cash, or any combination thereof. Optional Redemption - On or after June 30, 2024, the 2021 Convertible Notes will become redeemable at the Company’s option in the event the closing sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days during any 30 consecutive trading day period. The redemption price is equivalent to the principal amount of the 2021 Convertible Notes called for redemption, plus accrued and unpaid interest. If, following the Company’s delivery of a redemption notice, the 2021 Convertible Notes are converted pursuant to the Holders’ Conversion Rights, the Company is required to make an additional cash payment to the converting Holder equal to the present value of all interest payments the Holder would have been entitled to receive had such 2021 Convertible Notes remained outstanding until June 30, 2026 (the “interest make-whole payment”). The present value is calculated using a discount rate equal to the risk-free rate plus 50 basis points and assuming interest accrued at the cash interest rate of 5% per year. Contingent Redemption - Upon the occurrence of certain events, the Holder may require the Company to repurchase all or part of the principal amount of the 2021 Convertible Notes at a price equivalent to the principal amount of such 2021 Convertible Notes, plus accrued and unpaid interest. Such events include fundamental changes to the Company’s ownership and the delisting of the Company’s common stock from the Nasdaq. The occurrence of such events may result in the acceleration of the principal amount of the Convertible Notes, plus accrued and unpaid interest. Embedded Derivatives - The interest make-whole payment can be triggered only in connection with an induced conversion, and therefore represents an adjustment to the settlement amount of the embedded conversion feature. Because this adjustment is calculated in a manner in which the cash payout may exceed the time value of the embedded conversion feature, the embedded conversion feature is precluded from being considered indexed to the Company’s own stock. Therefore, the embedded conversion feature does not qualify for the scope exceptions to derivative accounting prescribed by Accounting Standards Codification 815, Derivatives and Hedging (“ASC 815”). The initial fair value of the embedded conversion feature was estimated to be $29,866, which the Company bifurcated from the 2021 Convertible Notes and accounts for separately. The embedded conversion feature is presented on the consolidated balance sheets as a component of the 2021 Convertible Notes. The Company estimated the fair value of the embedded conversion feature using a binomial lattice model at the inception and on subsequent valuation dates. This model incorporates inputs such as the stock price of the Company, dividend yield, risk-free interest rate, the effective debt yield and expected volatility. The effective debt yield and volatility involve unobservable inputs classified as Level 3 of the fair value hierarchy. The assumptions used to determine the fair value of the embedded conversion feature as of July 7, 2021 (the inception) and December 31, 2021 and are as follows: July 7, December 31, 2021 Term 5 years 4.50 years Dividend yield — % — % Risk-free interest rate 0.8 % 1.2 % Volatility 55.0 % 60.0 % Effective debt yield 13.7 % 19.0 % As of December 31, 2021, the fair value of the embedded conversion feature was $12,359. The Company recognized a gain of $17,507 attributable to the change in fair value of the embedded conversion feature during the year ended December 31, 2021. Debt Issuance Costs - The Company incurred $4,194 of placement, advisory and legal fees in connection with the issuance of the 2021 Convertible Notes, including $3,000 paid to B. Riley Securities, Inc., a related party of the Company. The debt issuance costs were allocated to the 2021 Convertible Notes and the embedded conversion feature in proportion to the allocation of proceeds resulting from the bifurcation of the embedded conversion feature. $2,942 of the issuance costs were allocated to the 2021 Convertible Notes. These costs were accounted for as debt issuance costs and recorded as a reduction to the carrying value of the 2021 Convertible Notes. The remaining $1,252 was allocated to the embedded conversion feature. Because the embedded conversion feature is carried at fair value, these costs were expensed as incurred and included in the interest expense line item on the consolidated statements of operations. The following table summarizes interest expense recognized for the year ended December 31, 2021: For the year ended December 31, 2021 Contractual interest expense $ 2,900 Amortization of debt discount 1,545 Amortization of debt issuance costs 152 Total $ 4,597 The 2021 Convertible Notes as of December 31, 2021 are comprised of the following: December 31, 2021 Principal $ 102,900 Unamortized debt discount (28,321) Unamortized debt issuance costs (2,790) Embedded conversion feature 12,359 Aggregate carrying value $ 84,148 The Company elected to repay the contractual interest due on December 30, 2021 in-kind as an increase to the principal amount. Therefore, $2,900 of contractual interest attributable to the 2021 Convertible Notes was recorded as addition to the convertible notes payable on the consolidated balance sheets. Legacy Convertible Notes During the years ended December 31, 2020 and 2019, the Company issued convertible notes payable with aggregate principals of $5,469 and $19,524, respectively (the “Legacy Convertible Notes”). The Legacy 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 Legacy 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 this section encompass the Legacy Convertible Notes. Phase I Convertible Notes Payable -related party The Legacy 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 (discussed below), 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 Legacy 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 18 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 Legacy 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 18 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. The fair value of both the Company’s Legacy Convertible Notes and the embedded derivative liability are classified within Level 3 of the fair value hierarchy. For the year ended December 31, 2020, embedded derivative liabilities with initial fair value of $411 was recognized. Embedded derivative assets with the initial fair value of $181 and the 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 sheets and had fair values of $1,681. The embedded derivatives were fair valued through the Merger date. During the years ended December 31, 2020 and 2019, a change in fair value of the embedded derivative resulted in a gain of $2,092 and a loss of $716, 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 was 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 the obligation, therefore, 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 years 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 discussed in Note 2, the Legacy 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 The following is a summary of the Company’s long-term indebtedness: December 31, 2021 December 31, 2020 Paycheck Protection Program loan payable $ — $ 1,257 Equipment financing facility 6,371 — Other — 94 Total 6,371 1,351 Less: long-term debt, current portion (1,644) (924) Long-term debt $ 4,727 $ 427 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 certify that the loan was used in accordance with the requirements and provide supporting documentation. The Company used all proceeds from the PPP Loan to retain our employees, maintain payroll, lease and utility obligations and pay other operational expenses to support business continuity throughout the Covid-19 pandemic. During the third quarter of 2021, the Company was approved for loan forgiveness by the SBA. Consequently, during the year ended December 31, 2021, the Company recorded a gain on debt forgiveness of $1,273 on the consolidated statements of operations. Equipment Financing Facility On September 30, 2021, the Company entered into an agreement (the “Equipment Financing Agreement”) with Trinity Capital Inc. ("Trinity") for a $25,000 equipment financing facility (the "Equipment Financing Facility"), the proceeds of which will be used to acquire certain manufacturing equipment, subject to Trinity's approval. Upon execution of the Equipment Financing Agreement, the Company borrowed $7,000 (the “Initial Draw”) against the $25,000 commitment. The remaining commitment of $18,000 is fundable upon the Company's request no later than September 30, 2022, in increments of not less than $500, (each a “Draw”). $188 of commitment fee was paid at the closing, with $53 recorded as debt issuance cost for the Initial Draw and $135 recorded as prepaid expenses. On September 30, 2022, any unused portion of the remaining commitment will be subject to a non-utilization fee equal to 3% of the unused amount. Each Draw is executed under a separate payment schedule (a “Schedule”) that constitutes a separate financial instrument. The financing fees included in each Schedule are established through monthly payment factors determined by Trinity. Such monthly payment factors are based on the Prime Rate reported in The Wall Street Journal in effect on the first day of the month in which a Schedule is executed. The Prime Rate applicable to the Initial Draw is 3.25%. The monthly payment factors will be adjusted for each subsequent Schedule, using the then existing Prime Rate, but no less than the monthly payment factor set forth in the Initial Draw. Debt issuance costs of $175 were withheld by Trinity from the Initial Draw. The Initial Draw is payable in monthly installments of $204 ending March 31, 2025, along with an end-of-term fee of $70 due on March 31, 2025. The effective interest rate is 14.3%. The Company may repay the Initial Draw prior to March 31, 2025 by terminating the Equipment Financing Agreement. On the proposed termination date, the Company is required to pay Trinity an amount equal to the sum of all monthly installments that would have otherwise become payable through the maturity date, the end-of-term payment, and, if applicable, the non-utilization fee. The Initial Draw is collateralized by certain equipment and other property held at the Hi-Power manufacturing facility. Subsequent Draws will be collateralized by the equipment financed through the respective draws. In connection with the Equipment Financing Agreement, the Company executed a corporate guaranty in favor of Trinity. As the guarantor, the Company unconditionally and irrevocably guarantees the obligation under the Financing Agreement.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Notes Payable	Notes PayableIn connection with the Hi-Power acquisition (Refer to Note 3), the Company agreed to pay an aggregate purchase price of $25,000. $5,000 of the $25,000 purchase price was paid in May 2021. The fair value of the notes payable was estimated using active market quotes, based on our current incremental borrowing rates for similar types of borrowing arrangements, which were Level 2 inputs. Based on the analysis performed, the carrying value of the remaining payments of the notes payable was recorded as debt, which includes a current portion of $4,926 and a long-term portion of $13,769 as of December 31, 2021.

Long-term Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-term Debt	Convertible Notes Payable 2021 Convertible Notes On July 6, 2021, the Company entered into an investment agreement (the “Investment Agreement”) with Spring Creek Capital, LLC, a wholly-owned, indirect subsidiary of Koch relating to the issuance and sale to Koch of the 2021 Convertible Notes in the aggregate principal amount of $100,000. The transactions contemplated by the Investment Agreement closed on July 7, 2021 (the “Issue Date”). The Maturity Date of the 2021 Convertible Notes is June 30, 2026, subject to earlier conversion, redemption, or repurchase. Right after the issuance, Koch beneficially owned approximately 14% of the Company’s outstanding common stock. The 2021 Convertible Notes are senior unsecured obligations of the Company and rank equal in right of payment to all senior unsecured indebtedness of the Company, and will rank senior in right of payment to any indebtedness that is contractually subordinated to the 2021 Convertible Notes. Contractual Interest Rates - The 2021 Convertible Notes were issued at par and bear interest at a rate of 5% per year if interest is paid in cash, or, if interest is paid in-kind as an increase in the principal amount, at a rate of 6% per year. Interest on the 2021 Convertible Notes is payable semi-annually in arrears on June 30 and December 30. The Company, at its option, is permitted to settle each semi-annual interest payment in cash, in-kind, or any combination thereof. Conversion Rights - The 2021 Convertible Notes are convertible at the option of the Holder at any time prior to the maturity date at an initial conversion rate of 49.9910 shares of the Company’s common stock per $1,000 of capitalized principal (the “Holder’s Conversion Rights”). The effective conversion price is approximately $20.00 per share. The conversion rate is subject to adjustment upon the occurrence of certain dilutive events such as stock splits and combinations, stock dividends, mergers and spin-off. For the year ended December 31, 2021, there were no adjustments to conversion rate. As of December 31, 2021, 5,144,074 shares of the Company’s common stock were issuable upon conversion of the 2021 Convertible Notes including the principal and interest payment in-kind. The Company has the right to settle conversions in shares of common stock, cash, or any combination thereof. Optional Redemption - On or after June 30, 2024, the 2021 Convertible Notes will become redeemable at the Company’s option in the event the closing sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days during any 30 consecutive trading day period. The redemption price is equivalent to the principal amount of the 2021 Convertible Notes called for redemption, plus accrued and unpaid interest. If, following the Company’s delivery of a redemption notice, the 2021 Convertible Notes are converted pursuant to the Holders’ Conversion Rights, the Company is required to make an additional cash payment to the converting Holder equal to the present value of all interest payments the Holder would have been entitled to receive had such 2021 Convertible Notes remained outstanding until June 30, 2026 (the “interest make-whole payment”). The present value is calculated using a discount rate equal to the risk-free rate plus 50 basis points and assuming interest accrued at the cash interest rate of 5% per year. Contingent Redemption - Upon the occurrence of certain events, the Holder may require the Company to repurchase all or part of the principal amount of the 2021 Convertible Notes at a price equivalent to the principal amount of such 2021 Convertible Notes, plus accrued and unpaid interest. Such events include fundamental changes to the Company’s ownership and the delisting of the Company’s common stock from the Nasdaq. The occurrence of such events may result in the acceleration of the principal amount of the Convertible Notes, plus accrued and unpaid interest. Embedded Derivatives - The interest make-whole payment can be triggered only in connection with an induced conversion, and therefore represents an adjustment to the settlement amount of the embedded conversion feature. Because this adjustment is calculated in a manner in which the cash payout may exceed the time value of the embedded conversion feature, the embedded conversion feature is precluded from being considered indexed to the Company’s own stock. Therefore, the embedded conversion feature does not qualify for the scope exceptions to derivative accounting prescribed by Accounting Standards Codification 815, Derivatives and Hedging (“ASC 815”). The initial fair value of the embedded conversion feature was estimated to be $29,866, which the Company bifurcated from the 2021 Convertible Notes and accounts for separately. The embedded conversion feature is presented on the consolidated balance sheets as a component of the 2021 Convertible Notes. The Company estimated the fair value of the embedded conversion feature using a binomial lattice model at the inception and on subsequent valuation dates. This model incorporates inputs such as the stock price of the Company, dividend yield, risk-free interest rate, the effective debt yield and expected volatility. The effective debt yield and volatility involve unobservable inputs classified as Level 3 of the fair value hierarchy. The assumptions used to determine the fair value of the embedded conversion feature as of July 7, 2021 (the inception) and December 31, 2021 and are as follows: July 7, December 31, 2021 Term 5 years 4.50 years Dividend yield — % — % Risk-free interest rate 0.8 % 1.2 % Volatility 55.0 % 60.0 % Effective debt yield 13.7 % 19.0 % As of December 31, 2021, the fair value of the embedded conversion feature was $12,359. The Company recognized a gain of $17,507 attributable to the change in fair value of the embedded conversion feature during the year ended December 31, 2021. Debt Issuance Costs - The Company incurred $4,194 of placement, advisory and legal fees in connection with the issuance of the 2021 Convertible Notes, including $3,000 paid to B. Riley Securities, Inc., a related party of the Company. The debt issuance costs were allocated to the 2021 Convertible Notes and the embedded conversion feature in proportion to the allocation of proceeds resulting from the bifurcation of the embedded conversion feature. $2,942 of the issuance costs were allocated to the 2021 Convertible Notes. These costs were accounted for as debt issuance costs and recorded as a reduction to the carrying value of the 2021 Convertible Notes. The remaining $1,252 was allocated to the embedded conversion feature. Because the embedded conversion feature is carried at fair value, these costs were expensed as incurred and included in the interest expense line item on the consolidated statements of operations. The following table summarizes interest expense recognized for the year ended December 31, 2021: For the year ended December 31, 2021 Contractual interest expense $ 2,900 Amortization of debt discount 1,545 Amortization of debt issuance costs 152 Total $ 4,597 The 2021 Convertible Notes as of December 31, 2021 are comprised of the following: December 31, 2021 Principal $ 102,900 Unamortized debt discount (28,321) Unamortized debt issuance costs (2,790) Embedded conversion feature 12,359 Aggregate carrying value $ 84,148 The Company elected to repay the contractual interest due on December 30, 2021 in-kind as an increase to the principal amount. Therefore, $2,900 of contractual interest attributable to the 2021 Convertible Notes was recorded as addition to the convertible notes payable on the consolidated balance sheets. Legacy Convertible Notes During the years ended December 31, 2020 and 2019, the Company issued convertible notes payable with aggregate principals of $5,469 and $19,524, respectively (the “Legacy Convertible Notes”). The Legacy 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 Legacy 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 this section encompass the Legacy Convertible Notes. Phase I Convertible Notes Payable -related party The Legacy 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 (discussed below), 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 Legacy 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 18 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 Legacy 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 18 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. The fair value of both the Company’s Legacy Convertible Notes and the embedded derivative liability are classified within Level 3 of the fair value hierarchy. For the year ended December 31, 2020, embedded derivative liabilities with initial fair value of $411 was recognized. Embedded derivative assets with the initial fair value of $181 and the 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 sheets and had fair values of $1,681. The embedded derivatives were fair valued through the Merger date. During the years ended December 31, 2020 and 2019, a change in fair value of the embedded derivative resulted in a gain of $2,092 and a loss of $716, 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 was 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 the obligation, therefore, 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 years 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 discussed in Note 2, the Legacy 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 The following is a summary of the Company’s long-term indebtedness: December 31, 2021 December 31, 2020 Paycheck Protection Program loan payable $ — $ 1,257 Equipment financing facility 6,371 — Other — 94 Total 6,371 1,351 Less: long-term debt, current portion (1,644) (924) Long-term debt $ 4,727 $ 427 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 certify that the loan was used in accordance with the requirements and provide supporting documentation. The Company used all proceeds from the PPP Loan to retain our employees, maintain payroll, lease and utility obligations and pay other operational expenses to support business continuity throughout the Covid-19 pandemic. During the third quarter of 2021, the Company was approved for loan forgiveness by the SBA. Consequently, during the year ended December 31, 2021, the Company recorded a gain on debt forgiveness of $1,273 on the consolidated statements of operations. Equipment Financing Facility On September 30, 2021, the Company entered into an agreement (the “Equipment Financing Agreement”) with Trinity Capital Inc. ("Trinity") for a $25,000 equipment financing facility (the "Equipment Financing Facility"), the proceeds of which will be used to acquire certain manufacturing equipment, subject to Trinity's approval. Upon execution of the Equipment Financing Agreement, the Company borrowed $7,000 (the “Initial Draw”) against the $25,000 commitment. The remaining commitment of $18,000 is fundable upon the Company's request no later than September 30, 2022, in increments of not less than $500, (each a “Draw”). $188 of commitment fee was paid at the closing, with $53 recorded as debt issuance cost for the Initial Draw and $135 recorded as prepaid expenses. On September 30, 2022, any unused portion of the remaining commitment will be subject to a non-utilization fee equal to 3% of the unused amount. Each Draw is executed under a separate payment schedule (a “Schedule”) that constitutes a separate financial instrument. The financing fees included in each Schedule are established through monthly payment factors determined by Trinity. Such monthly payment factors are based on the Prime Rate reported in The Wall Street Journal in effect on the first day of the month in which a Schedule is executed. The Prime Rate applicable to the Initial Draw is 3.25%. The monthly payment factors will be adjusted for each subsequent Schedule, using the then existing Prime Rate, but no less than the monthly payment factor set forth in the Initial Draw. Debt issuance costs of $175 were withheld by Trinity from the Initial Draw. The Initial Draw is payable in monthly installments of $204 ending March 31, 2025, along with an end-of-term fee of $70 due on March 31, 2025. The effective interest rate is 14.3%. The Company may repay the Initial Draw prior to March 31, 2025 by terminating the Equipment Financing Agreement. On the proposed termination date, the Company is required to pay Trinity an amount equal to the sum of all monthly installments that would have otherwise become payable through the maturity date, the end-of-term payment, and, if applicable, the non-utilization fee. The Initial Draw is collateralized by certain equipment and other property held at the Hi-Power manufacturing facility. Subsequent Draws will be collateralized by the equipment financed through the respective draws. In connection with the Equipment Financing Agreement, the Company executed a corporate guaranty in favor of Trinity. As the guarantor, the Company unconditionally and irrevocably guarantees the obligation under the Financing Agreement.

Contingently Redeemable Preferr

Contingently Redeemable Preferred Units	12 Months Ended
	Dec. 31, 2021
Temporary Equity Disclosure [Abstract]
Contingently Redeemable Preferred Units	Contingently Redeemable Preferred Units For the year ended December 31, 2020, and 2019, the Company had Series C, Series D, and 2019 Bridge Preferred Units ("EES Preferred Units) 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; and • 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 sheets. 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 15, 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 15 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

Warrants Liability

Warrants Liability	12 Months Ended
	Dec. 31, 2021
Other Liabilities Disclosure [Abstract]
Warrants Liability	Warrants Liability - Related Party The Company’s outstanding warrants were issued by BMRG in connection with its initial public offering (the “Public Warrants”) and concurrent private placement (the “Private Warrants” and, together with the Public Warrants, the “Warrants”) on May 22, 2020. Upon consummation of the Merger on November 16, 2020, the Public Warrants and Private Placement Warrants were set to become exercisable on May 22, 2021 for shares of the Company’s common stock with the same terms and exercise provisions prior to the Merger. The Private Placement Warrants meet the definition of a derivative. On the basis of the SEC Division of Corporation Finance’s April 12, 2021 Public Statement-Staff Statement on Accounting and Reporting Considerations for Warrants Issued by Special Purpose Acquisition Companies (“SPACS”), the Private Placement Warrants do not meet the scope exception as prescribed by ASC 815-40, Derivatives and Hedging—Contracts in Entity’s Own Equity . Accordingly, the Company recognized the Private Placement Warrants as of the Merger Date on November 16, 2020 at fair value and classified them as a liability in the Company’s consolidated balance sheets. Thereafter, changes in fair value are recognized in earnings as a derivative gain (loss) in the Company’s consolidated statements of operations.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Since 2012, the Company 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 stock 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. In 2021, the Company reserved an additional 498,021 shares for the 2020 Incentive Plan. The 2020 Incentive Plan became effective immediately upon the Closing of the Merger and all equity granted under the 2012 Plan was converted into equivalent equity under the 2020 Incentive Plan. As of December 31, 2021 and 2020, the Company has stock options and restricted stock units issued under the 2020 Incentive Plan. Stock-based compensation expense included in the consolidated statements of operations was as follows: For the years ended December 31 2021 2020 2019 Stock options $ 3,809 $ 4,104 $ 131 Restricted stock units 11,249 977 4 Total $ 15,058 $ 5,081 $ 135 The stock compensation has been recorded in cost of goods sold, research and development expenses and selling, general and administrative expenses in the consolidated statements of operations. The following table summarizes stock option activity during the years ended December 31, 2021, 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 Weighted-Average 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 Granted 114,429 $ 18.07 Cancelled/Forfeited (110,768) $ 13.02 Exercised (123,837) $ 8.67 Options Outstanding at December 31, 2021 2,023,460 $ 9.51 6.3 Options Exercisable at December 31, 2021 1,124,199 $ 9.55 7.0 A summary of restricted stock units (RSU) activity for the year ended December 31, 2021 under our 2020 Incentive Plan is as follows: Units Weighted-Average RSU Outstanding at January 1, 2020 42,318 $ 13.46 Granted 2,580,670 $ 16.62 Cancelled/Forfeited (273,632) $ 14.98 Vested (154,600) $ 16.50 RSU Outstanding at December 31, 2021 2,194,756 $ 16.36 As of December 31, 2021 and 2020, 2,282,906 and 3,825,176 shares remain for future issuance, respectively. Options vest generally over three five Unrecognized stock compensation expenses amounted to $31,487 and included $27,980 attributable to RSUs, and $3,507 attributable to stock options, which are both expected to be recognized over the next four years. The weighted average assumptions used to determine the fair value of options granted in 2021, 2020 and 2019 are as follows: 2021 2020 2019 Volatility 58.86 % 52.99 % 58.20 % Risk free interest rate 0.67 % 0.39 % 1.89 % Expected life (years) 4.18 5.19 6.25 Dividend yield 0 % 0 % 0 % The RSUs issued were valued at the stock prices of the Company on the grant date. The weighted average grant date fair value of all options granted was $8.08, $5.38, and $1.21 per option for the years ended December 31, 2021, 2020, and 2019 respectively.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	Leases Adoption of ASU 2016-02 As discussed in Note 1, on January 1, 2021, the Company adopted ASU 2016-02, "Leases (Topic 842)," and the related amendments (collectively "ASC 842"). The Company elected the modified retrospective approach, under which results and disclosures for periods before January 1, 2021 were not adjusted for the new standard and the cumulative effect of the change in accounting, is recognized through accumulated deficit at the date of adoption. The Standard establishes a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the consolidated balance sheets for all leases. Leases are classified as either finance or operating, with classification affecting the pattern of expense recognition in the consolidated statements of operations. The Standard provides entities with several practical expedient elections. Among them, the Company elected the package of practical expedients that permits the Company to not reassess prior conclusions related to its leasing arrangements, lease classifications and initial direct costs. In addition, the Company has elected the practical expedients to not separate lease and non-lease components, to use hindsight in determining the lease terms and impairment of ROU assets, and to not apply the Standard’s recognition requirements to short-term leases with a term of 12 months or less. Lessee The adoption of the Standard did not have a material effect on the Company’s consolidated statements of operations or consolidated statements of cash flows. Upon adoption, the Company recorded a $3,662 operating lease ROU asset and a $4,465 operating lease liability. The adoption of the New Lease Accounting Standard had no impact on accumulated deficit. At December 31, 2021, finance leases, which were previously classified as capital leases under ASC 840, are included in Property and equipment, net. The adoption did not affect the balance sheet classification of the capital lease obligations (known as finance lease liabilities effective January 1, 2021). The Company leases machinery, manufacturing facilities, office space, land, and equipment under both operating and finance leases. The Company determines if an arrangement is a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. Lease assets and lease liabilities as of December 31, 2021 were as follows: Leases Classification on Balance Sheet As of December 31, 2021 Assets ROU - operating lease assets Operating lease right-of-use asset, net $ 3,468 Finance lease assets Property and equipment, net 28 Total lease assets $ 3,496 Classification on Balance Sheet As of December 31, 2021 Liabilities Current Operating lease liability Operating lease liability, current portion $ 1,084 Finance lease liability Other current liabilities 8 Non-Current Operating lease liability Operating lease liability, long-term 3,224 Finance lease liability Other liabilities 17 Total lease liabilities $ 4,333 Operating lease costs for the years ended December 31, 2021, 2020, and 2019 were $1,158, $959, and $1,291, respectively. As of December 31, 2021, the weighted average remaining term (in years) for the operating lease was 4.15 years and the weighted average discount rate was 3.3%. The weighted average remaining term (in years) for the finance lease was 3.47 years and the weighted average discount rate was 12.5%. Future maturity of lease liability are as follows: Operating lease Financing lease Total 2022 $ 1,210 $ 12 $ 1,222 2023 850 8 858 2024 916 8 924 2025 986 8 994 2026 601 1 602 Later years — — — Total minimum lease payments $ 4,563 $ 37 $ 4,600 Less amounts representing interest 255 12 267 Present value of minimum lease payments $ 4,308 $ 25 $ 4,333 The future minimum lease payments from our 2020 Form 10-K as filed in accordance with Leases (Topic 840) in each of the next five years and thereafter 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 Lessor The Company leases energy storage systems to one customer with a 20-year term through sales-type leases. Leases offered by the Company include purchase options during the lease term with a bargain purchase option at the end of the term. At the time of accepting a lease that qualifies as a sales-type lease, the Company records the gross amount of lease payments receivable, estimated residual value of the leased equipment and unearned finance income. The unearned finance income is recognized interest income over the lease term using the interest method. For the year ended December 31, 2021, the Company recognized revenue of $353. Net sales-type lease receivables of $347, net of unearned finance income are recorded under other assets on the consolidated balance sheets.
Leases	Leases Adoption of ASU 2016-02 As discussed in Note 1, on January 1, 2021, the Company adopted ASU 2016-02, "Leases (Topic 842)," and the related amendments (collectively "ASC 842"). The Company elected the modified retrospective approach, under which results and disclosures for periods before January 1, 2021 were not adjusted for the new standard and the cumulative effect of the change in accounting, is recognized through accumulated deficit at the date of adoption. The Standard establishes a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the consolidated balance sheets for all leases. Leases are classified as either finance or operating, with classification affecting the pattern of expense recognition in the consolidated statements of operations. The Standard provides entities with several practical expedient elections. Among them, the Company elected the package of practical expedients that permits the Company to not reassess prior conclusions related to its leasing arrangements, lease classifications and initial direct costs. In addition, the Company has elected the practical expedients to not separate lease and non-lease components, to use hindsight in determining the lease terms and impairment of ROU assets, and to not apply the Standard’s recognition requirements to short-term leases with a term of 12 months or less. Lessee The adoption of the Standard did not have a material effect on the Company’s consolidated statements of operations or consolidated statements of cash flows. Upon adoption, the Company recorded a $3,662 operating lease ROU asset and a $4,465 operating lease liability. The adoption of the New Lease Accounting Standard had no impact on accumulated deficit. At December 31, 2021, finance leases, which were previously classified as capital leases under ASC 840, are included in Property and equipment, net. The adoption did not affect the balance sheet classification of the capital lease obligations (known as finance lease liabilities effective January 1, 2021). The Company leases machinery, manufacturing facilities, office space, land, and equipment under both operating and finance leases. The Company determines if an arrangement is a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. Lease assets and lease liabilities as of December 31, 2021 were as follows: Leases Classification on Balance Sheet As of December 31, 2021 Assets ROU - operating lease assets Operating lease right-of-use asset, net $ 3,468 Finance lease assets Property and equipment, net 28 Total lease assets $ 3,496 Classification on Balance Sheet As of December 31, 2021 Liabilities Current Operating lease liability Operating lease liability, current portion $ 1,084 Finance lease liability Other current liabilities 8 Non-Current Operating lease liability Operating lease liability, long-term 3,224 Finance lease liability Other liabilities 17 Total lease liabilities $ 4,333 Operating lease costs for the years ended December 31, 2021, 2020, and 2019 were $1,158, $959, and $1,291, respectively. As of December 31, 2021, the weighted average remaining term (in years) for the operating lease was 4.15 years and the weighted average discount rate was 3.3%. The weighted average remaining term (in years) for the finance lease was 3.47 years and the weighted average discount rate was 12.5%. Future maturity of lease liability are as follows: Operating lease Financing lease Total 2022 $ 1,210 $ 12 $ 1,222 2023 850 8 858 2024 916 8 924 2025 986 8 994 2026 601 1 602 Later years — — — Total minimum lease payments $ 4,563 $ 37 $ 4,600 Less amounts representing interest 255 12 267 Present value of minimum lease payments $ 4,308 $ 25 $ 4,333 The future minimum lease payments from our 2020 Form 10-K as filed in accordance with Leases (Topic 840) in each of the next five years and thereafter 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 Lessor The Company leases energy storage systems to one customer with a 20-year term through sales-type leases. Leases offered by the Company include purchase options during the lease term with a bargain purchase option at the end of the term. At the time of accepting a lease that qualifies as a sales-type lease, the Company records the gross amount of lease payments receivable, estimated residual value of the leased equipment and unearned finance income. The unearned finance income is recognized interest income over the lease term using the interest method. For the year ended December 31, 2021, the Company recognized revenue of $353. Net sales-type lease receivables of $347, net of unearned finance income are recorded under other assets on the consolidated balance sheets.

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement The Company’s financial instruments consist of cash and cash equivalents, restricted cash, the Public and Private Placement Warrants, accounts receivable, note receivable, accounts payable, and notes payable, convertible 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 table below summarizes the fair values of certain liabilities that are included within our accompanying consolidated balance sheets, and their designations among the three fair value measurement categories: December 31, 2021 December 31, 2020 (in thousands) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Liabilities Private Placement Warrants $ — $ 926 $ — $ — $ 2,701 $ — Embedded derivative liability within the 2021 Convertible Notes $ — $ — $ 12,359 $ — $ — $ — The following table presents a roll-forward of the activity of all liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2021 and 2020. December 31, 2021 December 31, 2020 Balance at beginning of the period $ — $ 1,681 Additions 29,866 411 Change in fair value included in earnings (17,507) (2,092) Balance at end of the period $ 12,359 $ — The estimated fair value of financial instruments not carried at fair value in the consolidated balance sheets was as follows: Level in fair value hierarchy December 31, 2021 December 31, 2020 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Notes payable 3 $ 18,695 $ 14,607 $ — $ — Equipment financing facility 3 $ 6,370 $ 5,951 $ — $ — 2021 Convertible Notes without embedded derivative liability 3 $ 71,789 $ 61,866 $ — $ — Paycheck Protection Program 2 $ — $ — $ 1,257 $ 1,222

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2021
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, 2021 and 2020, 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, 2021 and 2020, there were 53,786,632 and 48,943,082 common stocks issued and outstanding. Contingently Issuable Common Stock Following the closing of the Merger, and as additional consideration for the transaction, the Company was obligated to 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 5 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”). 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. Accordingly, 1,999,185 Shares were issued to the unitholders of EES. 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") were 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") were 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. 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 were released from restriction. Treasury Stock For the year ended December 31, 2021, the Company recorded treasury stock of $353 for shares withheld to pay the payroll tax liability of RSUs vested, which will be remitted in 2022. The treasury stock was immediately retired. 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 8,750,000 Public Warrants outstanding which became exercisable on May 22, 2021. For the year ended December 31, 2021, 1,747,746 Public Warrants were exercised. At December 31, 2021, there were 7,002,254 Public Warrants outstanding. Earnings (loss) 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. As we incurred a net loss for the years ended December 31, 2021 and 2020, the potential dilutive shares from stock options, restricted stock units, warrants, and convertible redeemable notes were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented. Therefore, basic and diluted EPS are computed using the same number of weighted average shares for the years ended December 31, 2021 and 2020. 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 years ended December 31 2021 2020 2019 Stock options and restricted stock units 4,218,216 2,185,954 392,838 Warrants 7,327,254 9,075,000 — Block B Sponsor Earnout Shares subject to restrictions — 859,000 — Contingently Issuable Common Stock — 2,000,000 — Convertible Notes (if converted) 5,144,074 — 7,655,908 Contingent redeemable preferred units — — 12,964,231 Disgorgement of short swing profits

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Based upon this review, the Company did not identify any subsequent events that would have required adjustment or disclosure in the financial statements.

Nature of Operations and Summ_2

Nature of Operations and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
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 PresentationCertain prior year amounts have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the reported results of operations.
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.
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. Restricted cash
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.
Accounts Receivable, net	Accounts Receivable, net 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 credit losses. The Company had $1,925 and $35 of accounts receivable as of December 31, 2021 and 2020, with $9 and $35 of allowances for credit loss recorded, respectively. The total allowance for credit losses was included in Accounts Receivable, Net on the consolidated balance sheets. The activity in the allowance for credit losses was as follows: December 31, 2021 December 31, 2020 Beginning of Period $ 35 $ — Credit Loss Expense 9 35 Write-offs (35) — End of Period $ 9 $ 35
Inventory, net	Inventory, net Inventories are stated at the lower of cost or net realizable value. Cost is computed using standard cost which approximates actual cost on a first-in, first-out basis. The Company records inventory when it takes delivery and title to the product according to the terms of each supply contract.
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.
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.
Business Combinations	Business Combinations The Company accounts for the acquisition of a business using the acquisition method of accounting and allocates the purchase price of acquired entities to the underlying tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values, with any excess recorded as goodwill. The operating results of acquired businesses are included in the Company’s results of operations beginning as of their effective acquisition dates. Additional information regarding the business acquisition can be found in Note 3.
Goodwill	Goodwill The Company accounts for goodwill as the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. Goodwill is not subject to amortization; rather, the Company tests goodwill for impairment annually or more frequently if an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of the asset below the carrying amount. The Company has the option to perform a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If this is the case, the quantitative assessment is required. If it is more likely than not that the fair value of the reporting unit is greater than its carrying amount, the quantitative goodwill impairment test is not required. In performing a qualitative assessment, the Company first assesses relevant factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a quantitative goodwill impairment test. The Company identifies and considers the significance of relevant key factors, events, and circumstances that could affect the fair value of the reporting unit. These factors include external factors such as macroeconomic, industry, and market conditions, as well as entity-specific factors, such as actual and planned financial performance. The Company completed the annual goodwill impairment test as of November 30, 2021, using a qualitative assessment for the reporting unit. The Company concluded that it is more likely than not that the fair value of the reporting unit is greater than the carrying amount, and a quantitative goodwill impairment test was not necessary. As a result of the annual assessment, there were no impairment charges for the year ended December 31, 2021.
Revenue from Contracts with Customers	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 upon shipment or delivery of the goods at the customer’s designated location and varies by contracts. In addition, the corresponding installation and commissioning services related to the systems are performance obligations satisfied over time as the respective services are performed. Further, extended warranties, maintenance and monitoring, and degradation guarantees 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 performance period. Transaction price is allocated to the various performance obligations based on the relative stand-alone selling prices of the promised goods and services. Stand-alone selling prices are either determined based on cost plus a reasonable margin or an adjusted market approach. 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 goods sold. 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. Assessment of Estimates of Variable Consideration and Determination of Transaction Price Many of the Company’s contracts with customers contain some component of variable consideration. The Company estimates variable consideration, such as refunds, penalties including liquidated damages, 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 estimates of variable consideration on a monthly basis and adjust the 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. 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. Practical Expedients and Exemptions As permitted by ASC 606, the Company elected to use certain practical expedients. The Company treats costs associated with obtaining new contracts as expenses when incurred if the amortization period of the asset recognized by the Company is one year or less. The election of the practical expedients results in accounting treatments that the Company believes are consistent with historical accounting policies and, therefore, the election of practical expedients does not have a material impact on the comparability of the financial statements.
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 two years and optional 20-year degradation guarantee, commencing upon commissioning. Costs to provide for warranty obligations are estimated and recorded as a liability at the time of recording the sale. Warranty reserves include management’s best estimate of the projected costs to repair or to replace any items under warranty, which is based on various factors, including the use of actual claim data to date, results of lab testing, factory quality data, field monitoring, and data on industry averages for similar products. Extended warranties and degradation guarantee 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.
Leases	Leases Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to calculate the present value represents our incremental borrowing rate and is calculated based on the treasury yield curve that commensurate with the term of each lease, and a spread representative of our borrowing costs. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Leases may be classified as either operating leases or finance leases. We have made an accounting policy election to not include leases with an initial term of 12 months or less on the balance sheets. Prior to the adoption of ASC 842, Leases , the Company recorded 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 were recorded as Deferred rent, which is included in other liabilities on the balance sheets. See Note 21 for additional information.
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.
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. The Company 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. The Company 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 included in the net operating loss at December 31, 2021 and December 31, 2020 that do not meet the more-likely-than-not threshold under ASC 740 are $348 and $322, respectively. See Note 12 for further information.
Earning (loss) Per Share	Earnings (loss) Per Share In accordance with the provisions of ASC Topic 260, Earnings per Share
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 carrying amounts for the Company’s financial instruments classified as current assets and liabilities, including cash and cash equivalents, restricted cash, trade accounts receivable and accrued expenses and accounts payable, approximate fair value due to their short maturities. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 - Quoted prices in active markets for identical assets or liabilities. Level 2 - Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Refer to Note 22 for additional information.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements Under the Jumpstart Our Business Startups (“JOBS”) Act, the Company qualified as an emerging growth company (“EGC”) and as such, elected not to opt out of the extended transition period for complying with new or revised accounting pronouncements. During the extended transition period, the Company was not subject to new or revised accounting standards applicable to public companies. Based on our public float calculation at June 30, 2021, the Company is deemed a Large Accelerated Filer under the U.S. Securities and Exchange Commission guidelines and ceased to qualify as an EGC effective December 31, 2021. The loss of EGC status resulted in losing the reporting exemptions noted above, and in particular requires our independent registered public accounting firm to provide an attestation report on the effectiveness of our internal control over financial reporting as of and for the year ended December 31, 2021 under Section 404(b) of the Sarbanes-Oxley Act and requires the adoption of ASU 2016-02 and ASU 2016-13 for the year ended December 31, 2021. On January 1, 2021, the Company adopted ASU 2016-02, Leases ("Topic 842"), using the transition method introduced by ASU 2018-11, which does not require revisions to comparative periods. Adoption of the new standard resulted in the recording of lease assets and lease liabilities of $3,662 and $4,465, respectively, as of January 1, 2021. The difference between the lease assets and lease liabilities primarily relates to deferred rent recorded in accordance with the previous leasing guidance. The new standard did not materially impact our consolidated statements of operations or statements of cash flows. On January 1, 2021, the Company adopted ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326), and the subsequent amendments. The standard sets forth an expected credit loss model which requires the measurement of expected credit losses for financial instruments based on historical experience, current conditions and reasonable and supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost, and certain off-balance sheet credit exposures. The adoption of this standard did not have a material impact on our consolidated financial statements. On January 1, 2021, the Company adopted ASU No. 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging-Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. This ASU simplifies the accounting for convertible instruments by eliminating the cash conversion and beneficial conversion feature models used to separately account for embedded conversion features as a component of equity. Instead, the entity will account for the convertible debt or convertible preferred stock securities as a single unit of account, unless the conversion feature requires bifurcation and recognition as derivatives. Additionally, the guidance requires entities to use the if-converted method for all convertible instruments in the diluted earnings per share calculation and include the effect of potential share settlement for instruments that may be settled in cash or shares. The adoption of this standard did not have a material impact on our 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. The Company has adopted this ASU in the first quarter of 2021. The adoption did not have an impact on our consolidated financial statements.

Nature of Operations and Summ_3

Nature of Operations and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Allowance for Credit Losses	The total allowance for credit losses was included in Accounts Receivable, Net on the consolidated balance sheets. The activity in the allowance for credit losses was as follows: December 31, 2021 December 31, 2020 Beginning of Period $ 35 $ — Credit Loss Expense 9 35 Write-offs (35) — End of Period $ 9 $ 35

Merger Agreement and Reverse _2

Merger Agreement and Reverse Recapitalization (Tables)	12 Months Ended
	Dec. 31, 2021
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, except 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

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the fair values of the assets acquired and liabilities assumed as of the Acquisition Date: Amount Inventory $ 2,666 Vendor deposits 818 Property and equipment, net 74 Goodwill 4,331 Accounts payable and accrued expenses (3,634) Provision for firm purchase commitments (3,890) Net assets acquired, net of cash and cash equivalents of $53 2 $ 365

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Information about Contract Liabilities from Contracts with Customers	The following table provides information about contract assets and contract liabilities from contracts with customers, which are included in other current assets and other current liabilities on the consolidated balance sheets, respectively. December 31, December 31, Contract assets $ 1,369 $ — Contract liabilities $ 849 $ 77

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2021
Inventory Disclosure [Abstract]
Components of Inventories	The following table provides information about inventory balances: December 31, 2021 December 31, 2020 Raw materials $ 11,898 $ — Work-in-process 43 — Finished goods 1,035 214 Total Inventory, net $ 12,976 $ 214

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Components of Property and Equipment, Net	As of December 31, 2021 and 2020, property and equipment, net consisted of the following: 2021 2020 Useful lives Equipment $ 13,489 $ 7,055 5 — 10 years Finance lease 226 201 5 years Furniture 808 211 5 — 10 years Leasehold Improvements 2,933 2,732 Lesser of useful life/remaining lease Tooling 3,053 523 2 — 3 years Total 20,509 10,722 Less: Accumulated Depreciation and Amortization (7,619) (5,069) $ 12,890 $ 5,653

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Estimated Future Amortization Expense of Intangible Assets	Estimated future amortization expense of intangible assets as of December 31, 2021 are as follows: 2022 $ 40 2023 40 2024 40 2025 40 2026 40 Thereafter 80 $ 280

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Components of Income Tax Expense (Benefit)	Income tax expense (benefit) for the years ended December 31, 2021, 2020, and 2019 was as follows: 2021 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: 2021 2020 2019 Income (loss) before income taxes $ (124,216) (70,643) $ (79,483) Statutory U.S. federal income tax (21%) (26,085) (14,835) (16,691) State and local income tax (6,592) (3,123) 1,548 Non-deductible convertible debt (3,676) 4,563 11,903 Non-deductible transaction cost — 66 — Non-deductible equity cost — 1,726 — Non-deductible warrant cost (373) 450 — Federal R&D Credit — 3,660 (1,002) Uncertain Tax Position — 322 — Valuation Allowance 36,541 7,253 4,215 Other 185 (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, 2021 and 2020 were as follows: 2021 2020 Deferred tax assets: NOL carryforwards $ 63,203 $ 40,278 Capital loss carryforwards 710 — Tax credit carryforwards 65 1,204 Goodwill 8,471 — Employee compensation 4,455 1,478 Accruals and reserves 1,586 1,744 Organizational costs 162 179 Lease Liability 1,185 — Interest Limitation 1,430 — Inventory 1,448 — Transaction costs 301 324 Deferred tax assets, gross $ 83,016 $ 45,207 Valuation allowance (80,415) (43,788) Total deferred tax assets, net $ 2,601 $ 1,419 Deferred tax liabilities: Fixed assets (1,073) (1,358) Investment in partnership — (61) Right of Use Asset (954) — Note payable (497) — Intangibles (77) — Deferred tax liabilities (2,601) (1,419) Total deferred tax asset (liability) $ — $ —
Unrecognized Tax Benefits Associated with Uncertain Tax Positions	The Company has unrecognized tax benefits associated with uncertain tax positions as of December 31, 2021, 2020, and 2019 as follows: 2021 2020 2019 Gross unrecognized tax benefits as of January 1 $ 722 $ — $ — Additions: Current year tax positions — 722 — Prior year tax positions — — — Rate change (3) — — Settlements — — — Lapse of statute of limitations — — — Gross unrecognized tax benefits as of December 31 $ 719 $ 722 $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	As of December 31, 2021 and 2020, accrued expenses consisted of the following: December 31, 2021 December 31, 2020 Accrued payroll $ 3,069 $ 2,146 Warranty accrual 2,112 — Accrued legal and professional fees 826 1,023 Other 1,667 1,924 Total $ 7,674 $ 5,093
Schedule of Product Warranty Liability	The following table summarizes product warranty activity for the year ended December 31, 2021. December 31, 2021 Accrued warranty - beginning of period $ — Additions for current year deliveries 2,343 Warranty costs incurred (231) Accrued warranty - end of period $ 2,112

Convertible Notes Payable (Tabl

Convertible Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Debt Assumptions	The assumptions used to determine the fair value of the embedded conversion feature as of July 7, 2021 (the inception) and December 31, 2021 and are as follows: July 7, December 31, 2021 Term 5 years 4.50 years Dividend yield — % — % Risk-free interest rate 0.8 % 1.2 % Volatility 55.0 % 60.0 % Effective debt yield 13.7 % 19.0 %
Interest Income and Interest Expense Disclosure	The following table summarizes interest expense recognized for the year ended December 31, 2021: For the year ended December 31, 2021 Contractual interest expense $ 2,900 Amortization of debt discount 1,545 Amortization of debt issuance costs 152 Total $ 4,597
Summary of Balances Recognized Upon Issuance of Convertible Notes	The 2021 Convertible Notes as of December 31, 2021 are comprised of the following: December 31, 2021 Principal $ 102,900 Unamortized debt discount (28,321) Unamortized debt issuance costs (2,790) Embedded conversion feature 12,359 Aggregate carrying value $ 84,148 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 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

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Summary of Long-term Indebtedness	The following is a summary of the Company’s long-term indebtedness: December 31, 2021 December 31, 2020 Paycheck Protection Program loan payable $ — $ 1,257 Equipment financing facility 6,371 — Other — 94 Total 6,371 1,351 Less: long-term debt, current portion (1,644) (924) Long-term debt $ 4,727 $ 427

Contingently Redeemable Prefe_2

Contingently Redeemable Preferred Units (Tables)	12 Months Ended
	Dec. 31, 2021
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 (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement, Cost by Plan	Stock-based compensation expense included in the consolidated statements of operations was as follows: For the years ended December 31 2021 2020 2019 Stock options $ 3,809 $ 4,104 $ 131 Restricted stock units 11,249 977 4 Total $ 15,058 $ 5,081 $ 135
Summary of Outstanding Stock Option Activity	The following table summarizes stock option activity during the years ended December 31, 2021, 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 Weighted-Average 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 Granted 114,429 $ 18.07 Cancelled/Forfeited (110,768) $ 13.02 Exercised (123,837) $ 8.67 Options Outstanding at December 31, 2021 2,023,460 $ 9.51 6.3 Options Exercisable at December 31, 2021 1,124,199 $ 9.55 7.0
Share-based Payment Arrangement, Restricted Stock Unit, Activity	A summary of restricted stock units (RSU) activity for the year ended December 31, 2021 under our 2020 Incentive Plan is as follows: Units Weighted-Average RSU Outstanding at January 1, 2020 42,318 $ 13.46 Granted 2,580,670 $ 16.62 Cancelled/Forfeited (273,632) $ 14.98 Vested (154,600) $ 16.50 RSU Outstanding at December 31, 2021 2,194,756 $ 16.36
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 2021, 2020 and 2019 are as follows: 2021 2020 2019 Volatility 58.86 % 52.99 % 58.20 % Risk free interest rate 0.67 % 0.39 % 1.89 % Expected life (years) 4.18 5.19 6.25 Dividend yield 0 % 0 % 0 %

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Assets And Liabilities, Lessee	Lease assets and lease liabilities as of December 31, 2021 were as follows: Leases Classification on Balance Sheet As of December 31, 2021 Assets ROU - operating lease assets Operating lease right-of-use asset, net $ 3,468 Finance lease assets Property and equipment, net 28 Total lease assets $ 3,496 Classification on Balance Sheet As of December 31, 2021 Liabilities Current Operating lease liability Operating lease liability, current portion $ 1,084 Finance lease liability Other current liabilities 8 Non-Current Operating lease liability Operating lease liability, long-term 3,224 Finance lease liability Other liabilities 17 Total lease liabilities $ 4,333
Lessee, Operating Lease, Liability, Maturity	Future maturity of lease liability are as follows: Operating lease Financing lease Total 2022 $ 1,210 $ 12 $ 1,222 2023 850 8 858 2024 916 8 924 2025 986 8 994 2026 601 1 602 Later years — — — Total minimum lease payments $ 4,563 $ 37 $ 4,600 Less amounts representing interest 255 12 267 Present value of minimum lease payments $ 4,308 $ 25 $ 4,333 The future minimum lease payments from our 2020 Form 10-K as filed in accordance with Leases (Topic 840) in each of the next five years and thereafter 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
Finance Lease, Liability, Fiscal Year Maturity	Future maturity of lease liability are as follows: Operating lease Financing lease Total 2022 $ 1,210 $ 12 $ 1,222 2023 850 8 858 2024 916 8 924 2025 986 8 994 2026 601 1 602 Later years — — — Total minimum lease payments $ 4,563 $ 37 $ 4,600 Less amounts representing interest 255 12 267 Present value of minimum lease payments $ 4,308 $ 25 $ 4,333 The future minimum lease payments from our 2020 Form 10-K as filed in accordance with Leases (Topic 840) in each of the next five years and thereafter 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

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The table below summarizes the fair values of certain liabilities that are included within our accompanying consolidated balance sheets, and their designations among the three fair value measurement categories: December 31, 2021 December 31, 2020 (in thousands) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Liabilities Private Placement Warrants $ — $ 926 $ — $ — $ 2,701 $ — Embedded derivative liability within the 2021 Convertible Notes $ — $ — $ 12,359 $ — $ — $ —
Liabilities measured at fair value on recurring basis using significant unobservable inputs (Level 3)	The following table presents a roll-forward of the activity of all liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2021 and 2020. December 31, 2021 December 31, 2020 Balance at beginning of the period $ — $ 1,681 Additions 29,866 411 Change in fair value included in earnings (17,507) (2,092) Balance at end of the period $ 12,359 $ —
Fair Value, Liabilities Measured on Recurring Basis	The estimated fair value of financial instruments not carried at fair value in the consolidated balance sheets was as follows: Level in fair value hierarchy December 31, 2021 December 31, 2020 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Notes payable 3 $ 18,695 $ 14,607 $ — $ — Equipment financing facility 3 $ 6,370 $ 5,951 $ — $ — 2021 Convertible Notes without embedded derivative liability 3 $ 71,789 $ 61,866 $ — $ — Paycheck Protection Program 2 $ — $ — $ 1,257 $ 1,222

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [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 years ended December 31 2021 2020 2019 Stock options and restricted stock units 4,218,216 2,185,954 392,838 Warrants 7,327,254 9,075,000 — Block B Sponsor Earnout Shares subject to restrictions — 859,000 — Contingently Issuable Common Stock — 2,000,000 — Convertible Notes (if converted) 5,144,074 — 7,655,908 Contingent redeemable preferred units — — 12,964,231

Nature of Operations and Summ_4

Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)segment	Jan. 01, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Product Warranty Liability [Line Items]
Restricted cash	$ 861		$ 0
Accounts receivable, net of allowances	1,925		35
Allowances for doubtful accounts	9		35
Unrecognized tax benefits, not likely to be recognized	$ 348		322
Number of operating segments | segment	1
Number of reportable segments | segment	1
Unrecognized tax benefits	$ 719		722	$ 0	$ 0
Operating lease right-of-use asset, net	3,468	$ 3,662	0
Present value of minimum lease payments	4,308	$ 4,465
Assets	169,175		138,264
Liabilities	136,728		17,479
Cash and cash equivalents	104,831		121,853
Convertible notes payable - related party	84,148		0
Notes payable	13,769		0
Long-term debt	6,371		1,351
Accumulated deficit	$ (416,527)		$ (292,311)
Maximum
Product Warranty Liability [Line Items]
Standard product warranty term	2 years

Nature of Operations and Summ_5

Nature of Operations and Summary of Significant Accounting Policies - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning of Period	$ 35	$ 0
Credit Loss Expense	9	35
Write-offs	(35)	0
End of Period	$ 9	$ 35

Merger Agreement and Reverse _3

Merger Agreement and Reverse Recapitalization - Narrative (Details) $ / shares in Units, $ in Thousands	Jan. 22, 2021tradingDay$ / shares	Dec. 16, 2020yearstradingDayshares	Nov. 16, 2020USD ($)YeartradingDay$ / sharesshares	Nov. 12, 2020$ / sharesshares	Dec. 31, 2021USD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)	Nov. 15, 2020USD ($)$ / 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
Conversion ratio			0.0576
Contingent equity, earnout period			5 years
Contingent equity, earnout period, shares issued (in shares)			2,000,000
Contingent equity, earnout period, threshold business days | tradingDay			5
Contingent equity, earnout period, threshold price (in usd per share) | $ / shares	$ 16		$ 16
Contingent equity, earnout period, threshold trading days | tradingDay	20		20
Contingent equity, earnout period, threshold consecutive trading days | tradingDay	30		30
Original fair value of the contingently issuable shares | $						$ 17,944
Contingent consideration, liability, earnout period			5 years
Contingent liability, earnout period, threshold trading days | tradingDay	20		20
Contingent liability, earnout period, threshold consecutive trading days | tradingDay	30		30
Contingent consideration, liability (in shares)			1,718,000
Release of Block A sponsor earnout shares from restriction (in shares)					0
Change in fair value, Sponsor Earnout Shares | $					$ 0	$ 8,220	$ 0
Measurement Input, Risk Free Interest Rate | Valuation Technique, Option Pricing Model
Business Acquisition [Line Items]
Fair value of contingently issuable common stock, measurement Input			0.0041
Fair value of sponsor earnout shares, measurement input			0.0041
Measurement Input, Price Volatility | Valuation Technique, Option Pricing Model
Business Acquisition [Line Items]
Fair value of contingently issuable common stock, measurement Input			0.55
Fair value of sponsor earnout shares, measurement input			0.55
Measurement Input, Expected Term | Valuation Technique, Option Pricing Model
Business Acquisition [Line Items]
Fair value of contingently issuable common stock, measurement Input			5
Fair value of sponsor earnout shares, measurement input | Year			5
Fair Value, Inputs, Level 3
Business Acquisition [Line Items]
Fair value measurement of sponsor earnout shares | $			$ 16,020
Common Stock
Business Acquisition [Line Items]
Release of Block A sponsor earnout shares from restriction (in shares)					859,000
Block A Sponsor Earnout Shares
Business Acquisition [Line Items]
Sponsor earnout shares subject to restriction (in shares)			859,000
Contingent consideration, liability, earnout period			5 years
Stock price trigger | $ / shares			$ 12
Contingent liability, earnout period, threshold trading days | tradingDay		20	20
Contingent liability, earnout period, threshold consecutive trading days | tradingDay		30
Block A Sponsor Earnout Shares | Common Stock
Business Acquisition [Line Items]
Release of Block A sponsor earnout shares from restriction (in shares)		859,000				859,000
Block B Sponsor Earnout Shares
Business Acquisition [Line Items]
Contingent consideration, liability, earnout period			5 years
Stock price trigger | $ / shares			$ 16
Contingent consideration, liability (in shares)			859,000
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		0.55
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 | years		5
BMRG
Business Acquisition [Line Items]
Redemption of BMRG shares prior to the merger (in shares)			6,442,195	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)			1,718,000
BMRG | Private Placement
Business Acquisition [Line Items]
Issuance of PIPE shares (in shares)			4,000,000
Issuance of PIPE shares (in usd per share) | $ / shares								$ 10
Issuance of PIPE Shares | $			$ 40,000

Merger Agreement and Reverse _4

Merger Agreement and Reverse Recapitalization - Summary of Reverse Recapitalization (Details) - USD ($) $ in Thousands	Nov. 16, 2020	Nov. 12, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Nov. 15, 2020
Business Acquisition [Line Items]
Common stock, shares outstanding (in shares)			53,786,632	48,943,082
Proceeds from capital infusion in reverse recapitalization	$ 142,345		$ 0	$ 142,345	$ 0
Common Stock
Business Acquisition [Line Items]
Net equity infusion from the merger (in shares)	18,364,805			18,364,805
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	6,442,195
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

Acquisition - Narrative (Detail

Acquisition - Narrative (Details) - USD ($) $ in Thousands	May 31, 2021	Apr. 09, 2021	Apr. 08, 2021	May 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019
Business Acquisition [Line Items]
Amount due at closing					$ 160	$ 0	$ 0
Loss on pre-existing agreement					30,368	1,262	$ 1,121
Long-term debt, current portion					1,644	924
Long-term debt					$ 4,727	$ 427
Hi-Power
Business Acquisition [Line Items]
Initial ownership interest		100.00%	49.00%		49.00%			49.00%
Notes Payable | Hi-Power Purchase Agreement
Business Acquisition [Line Items]
Long-term debt, current portion					$ 4,926
Long-term debt					$ 13,769
Hi-Power
Business Acquisition [Line Items]
Percentage of voting interests acquired		51.00%	51.00%
Aggregate purchase price		$ 25,000
Aggregate purchase price payment due this year		5,000
Aggregate purchase price payment due year one		5,000
Aggregate purchase price payment due year two		5,000
Aggregate purchase price payment due year three		5,000
Aggregate purchase price payment due year four		5,000
Amount due at closing				$ 5,000
Payment to terminate agreement		724
Consideration transferred, liabilities incurred	$ 5,000
Consideration transferred			$ 418
Fair value of previously held ownership interest			205
Loss on remeasurement			$ 7,480
Hi-Power | Holtec Power, Inc.
Business Acquisition [Line Items]
Aggregate purchase price		35,283
Amount due at closing		10,283
Fair value		33,474
Payment to terminate agreement		$ 32,750

Acquisition - Related Fair Valu

Acquisition - Related Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Apr. 09, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 4,331		$ 0
Hi-Power
Business Acquisition [Line Items]
Inventory		$ 2,666
Vendor deposits		818
Property and equipment, net		74
Goodwill		4,331
Accounts payable and accrued expenses		(3,634)
Provision for firm purchase commitments		(3,890)
Net assets acquired, net of cash and cash equivalents		365
Cash and cash equivalents		$ 53

Revenue Recognition - Informati

Revenue Recognition - Information about Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 1,369	$ 0
Contract liabilities	$ 849	$ 77

Revenue Recognition - Narrative

Revenue Recognition - Narratives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total revenue	$ 4,598	$ 219	$ 496
Increase (decrease) in contract asset	1,369
Increase (decrease) in contract liabilities	772	(223)
Revenue recognized in contract liabilities	$ 77	$ 184	$ 58
Revenue Benchmark | Customer 1 | Customer Concentration Risk
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Concentration risk percentage	36.80%	84.10%	36.30%
Revenue Benchmark | Customer 2 | Customer Concentration Risk
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Concentration risk percentage	21.40%	15.90%	31.40%
Revenue Benchmark | Customer 3 | Customer Concentration Risk
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Concentration risk percentage			26.10%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 849
Remaining performance obligation, expected timing of satisfaction, period	12 months
Transferred at Point in Time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total revenue	$ 4,562	$ 184	$ 496
Transferred over Time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total revenue	$ 36	$ 35	$ 0

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 11,898	$ 0
Work-in-process	43	0
Finished goods	1,035	214
Total Inventory, net	$ 12,976	$ 214

Property and Equipment, Net - C

Property and Equipment, Net - Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 20,509	$ 10,722
Less: Accumulated Depreciation and Amortization	(7,619)	(5,069)
Property and equipment, net	12,890	5,653
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 13,489	7,055
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful lives	10 years
Finance lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 226	201
Useful lives	5 years
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 808	211
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	$ 2,933	2,732
Tooling
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,053	$ 523
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 - N

Property and Equipment, Net - Narratives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 2,573	$ 1,518	$ 2,083
Impairment of property and equipment	$ 0	$ 0	$ 1,590

Intangible Assets - Narratives

Intangible Assets - Narratives (Details) - Patents - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	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	$ 40

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
2022	$ 40
2023	40
2024	40
2025	40
2026	40
Thereafter	80
Total	$ 280	$ 320

Investment in Unconsolidated _2

Investment in Unconsolidated Joint Venture (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 09, 2021	Apr. 08, 2021	Aug. 31, 2019
Schedule of Equity Method Investments [Line Items]
Contribution made to the JV	$ 4,000	$ 3,020	$ 768
Investment income (loss) from unconsolidated joint venture under the equity method of accounting	440	127	$ (178)
Investment in joint venture	$ 0	$ 3,736
Hi-Power
Schedule of Equity Method Investments [Line Items]
Initial estimated financial commitment						$ 4,100
Initial ownership interest	49.00%			100.00%	49.00%	49.00%

Notes Receivable, net and Var_2

Notes Receivable, net and Variable interest entities (“VIEs”) Consideration (Details) - Variable Interest Entity, not primary beneficiary - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Loan commitment on the consolidated balance sheet	$ 3,650	$ 100
Financing receivable, allowance for credit loss	$ 6	$ 0

Commitment and Contingencies (D

Commitment and Contingencies (Details) $ in Thousands	Dec. 31, 2021USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual	$ 382
Batteries
Loss Contingencies [Line Items]
Non-cancellable purchase commitment	$ 5,370

Grant Expense, Net (Details)

Grant Expense, Net (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)grant	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Other Income and Expenses [Abstract]
Number of grants approved | grant	2
Grants approval amount	$ 7,000
Grant expense (income), net	269	$ 913	$ (469)
Grant income	2,025	381	984
Grant costs	2,294	1,294	515
Grant payments received	0	1,531	$ 3,209
Deferred grant income	0	1,136
Grants receivable	$ 1,020	$ 131

Income Taxes - Narratives (Deta

Income Taxes - Narratives (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 08, 2021	Apr. 09, 2021	Apr. 08, 2021
Operating Loss Carryforwards [Line Items]
Net loss before income taxes for domestic operations	$ (124,216,000)	$ (70,643,000)	$ (79,483,000)
Tax provision (benefit)	0	0	$ 0
Convertible notes payable, net	6,371,000	1,351,000
Increase (decrease) in valuation allowance	(36,627,000)
Valuation allowance	80,415,000	43,788,000
Valuation allowance to be allocated to additional paid-in capital when released	1,762,000
Valuation allowance to be released through continuing operations	78,653,000
Unrecognized tax benefits that would impact effective tax rate	0
Hi-Power
Operating Loss Carryforwards [Line Items]
Percentage of voting interests acquired					51.00%	51.00%
Tax deductible goodwill					$ 36,768,000
Paycheck Protection Program
Operating Loss Carryforwards [Line Items]
Convertible notes payable, net	0	1,257,000		$ 1,273,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
NOL carryforwards	263,270,000	173,868,000
NOL subject to expiration	89,051,000
NOL with an indefinite carryforward period	174,219,000
Domestic Tax Authority | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credits	3,733,000	4,603,000
Amount federal R&D credits will expire unused	3,733,000	4,603,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
NOL carryforwards	125,855,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credits	$ 65,000	$ 1,131,000

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current expense (benefit):
U.S. federal	$ 0	$ 0	$ 0
U.S. state and local	0	0	0
Total current income tax (benefit) provision	0	0	0
Deferred expense (benefit):
U.S. federal	0	0	0
U.S. state and local	0	0	0
Total deferred income tax (benefit) provision	0	0	0
Total income tax (benefit) provision	$ 0	$ 0	$ 0

Income Taxes - Reconciliation f

Income Taxes - Reconciliation from Statutory to Effective Tax Rate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income (loss) before income taxes	$ (124,216,000)	$ (70,643,000)	$ (79,483,000)
Statutory U.S. federal income tax	(26,085,000)	(14,835,000)	(16,691,000)
State and local income tax	(6,592,000)	(3,123,000)	1,548,000
Non-deductible convertible debt	(3,676,000)	4,563,000	11,903,000
Non-deductible transaction cost	0	66,000	0
Non-deductible equity cost	0	1,726,000	0
Non-deductible warrant cost	(373,000)	450,000	0
Federal R&D Credit	0	3,660,000	(1,002,000)
Uncertain Tax Position	0	322,000	0
Valuation Allowance	36,541,000	7,253,000	4,215,000
Other	185,000	(82,000)	27,000
Total income tax (benefit) provision	$ 0	$ 0	$ 0
Effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
NOL carryforwards	$ 63,203	$ 40,278
Capital loss carryforwards	710	0
Tax credit carryforwards	65	1,204
Goodwill	8,471	0
Employee compensation	4,455	1,478
Accruals and reserves	1,586	1,744
Organizational costs	162	179
Lease Liability	1,185	0
Interest Limitation	1,430	0
Inventory	1,448	0
Transaction costs	301	324
Deferred tax assets, gross	83,016	45,207
Valuation allowance	(80,415)	(43,788)
Total deferred tax assets, net	2,601	1,419
Deferred tax liabilities:
Fixed assets	(1,073)	(1,358)
Investment in partnership	0	(61)
Right of Use Asset	(954)	0
Note payable	(497)	0
Intangibles	(77)	0
Deferred tax liabilities	(2,601)	(1,419)
Total deferred tax asset (liability)	$ 0	$ 0

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits Associated with Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Beginning balance	$ 722	$ 0	$ 0
Current year tax positions	0	722	0
Prior year tax positions	0	0	0
Rate change	(3)	0	0
Settlements	0	0	0
Lapse of statute of limitations	0	0	0
Ending balance	$ 719	$ 722	$ 0

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	Dec. 29, 2021	Dec. 01, 2021	Jul. 06, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 28, 2021	Apr. 08, 2021
Related Party Transaction [Line Items]
Payment made for debt issuance cost				$ 4,370,000	$ 0	$ 0
Interest payable, related party				2,900,000
Accounts payable and accrued expenses - related parties				1,200,000	2,517,000
Selling, general and administrative expenses				42,998,000	17,621,000	6,589,000
Provision for firm purchase commitments - related parties				0	1,585,000
Loss contingency accrual				$ 382,000
Related party, ownership interest qualifier				5.00%
Hellman Parties | Dilutive Effect Prior to Merger Agreement
Related Party Transaction [Line Items]
Equity interest issued or issuable (in shares)	159,977	300,000
B.Riley Securities, Inc
Related Party Transaction [Line Items]
Payment made for debt issuance cost			$ 3,000,000
Spring Creek Capital, LLC
Related Party Transaction [Line Items]
Notes receivable, related parties				$ 100,000,000
Director
Related Party Transaction [Line Items]
Costs incurred with related parties				69,000	19,000
Equity Method Investee | Holtec International
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties					2,382,000
Selling, general and administrative expenses				$ 30,368,000	1,262,000	$ 1,121,000
Affiliated Entity | Consultant Fees
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties					138,000
Affiliated Entity | B.Riley Securities, Inc
Related Party Transaction [Line Items]
Due from related parties, current					432,000
Corporate Joint Venture | Hi-Power
Related Party Transaction [Line Items]
Due from related parties, current					$ 278,000
Hellman Parties | Dilutive Effect Prior to Merger Agreement
Related Party Transaction [Line Items]
Estimated litigation liability								$ 5,000,000
Settlement deductible								$ 2,000,000
Loss contingency accrual							$ 1,200,000
Loss contingency accrual carrying amount, cash	$ 1,200,000
Loss contingency accrual, share equivalent	140,023

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued payroll	$ 826	$ 1,023
Warranty accrual	1,667	1,924
Accrued legal and professional fees	3,069	2,146
Other	2,112	0
Total	$ 7,674	$ 5,093

Accrued Expenses - Rollforward

Accrued Expenses - Rollforward (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Accrued warranty - beginning of period	$ 0
Additions for current year deliveries	2,343
Warranty costs incurred	(231)
Accrued warranty - end of period	$ 2,112

Convertible Notes Payable - Nar

Convertible Notes Payable - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 06, 2021USD ($)tradingDay$ / shares	Dec. 31, 2021USD ($)$ / shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Common stock, par value (in usd per share) | $ / shares		$ 0.0001	$ 0.0001
Payment made for debt issuance cost		$ 4,370	$ 0	$ 0
Long-term debt		6,371	$ 1,351
Koch Industries, Inc. | Eos
Debt Instrument [Line Items]
Ownership percentage by noncontrolling owners	14.00%
2021 Convertible Senior Notes
Debt Instrument [Line Items]
Conversion ratio	0.0499910
Conversion price per unit (in usd per share) | $ / shares	$ 20
Common stock, par value (in usd per share) | $ / shares	$ 5,144,074
Discount, beneficial conversion features	$ 29,866
Gain (loss) on beneficial conversion feature		17,507
Payment made for debt issuance cost	4,194
Unamortized discount and debt issuance costs, net	2,942
allocated beneficial conversion feature	1,252
Paid in kind interest		2,900
2021 Convertible Senior Notes | B.Riley Securities, Inc
Debt Instrument [Line Items]
Payment made for debt issuance cost	3,000
Senior Notes | 2021 Convertible Senior Notes
Debt Instrument [Line Items]
Principal	$ 100,000	102,900
Debt instruments, coupon rate	5.00%
Interest paid in kind, stated percentage	6.00%
Percentage of stock price	130.00%
Threshold trading days | tradingDay	20
Consecutive trading days | tradingDay	30
Discount, beneficial conversion features		12,359
Long-term debt		$ 84,148
Senior Notes | 2021 Convertible Senior Notes | Risk Free Rate
Debt Instrument [Line Items]
Debt Instrument, variable rate	0.50%

Convertible Notes Payable - Deb

Convertible Notes Payable - Debt Assumptions (Details)	Jul. 07, 2021	Dec. 31, 2021	Sep. 30, 2021
Debt Instrument [Line Items]
Annual effective interest rates in excess			14.30%
2021 Convertible Senior Notes
Debt Instrument [Line Items]
Debt instrument, term	5 years	4 years 6 months
Annual effective interest rates in excess	13.70%	19.00%
2021 Convertible Senior Notes | Dividend Yield
Debt Instrument [Line Items]
Debt Instrument, measurement input	0	0
2021 Convertible Senior Notes | Measurement Input, Risk Free Interest Rate
Debt Instrument [Line Items]
Debt Instrument, measurement input	0.008	0.012
2021 Convertible Senior Notes | Measurement Input, Price Volatility
Debt Instrument [Line Items]
Debt Instrument, measurement input	0.550	0.600

Convertible Notes Payable - Int

Convertible Notes Payable - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total		$ 1,545	$ 23,706	$ 49,708
2021 Convertible Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 2,900
Amortization of debt discount	1,545
Amortization of debt issuance costs		$ 152
Total	$ 4,597

Convertible Notes Payable - Dis

Convertible Notes Payable - Disaggregates the Net Carrying Value (Details) - USD ($) $ in Thousands	Jul. 06, 2021	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Convertible notes payable, net		$ 6,371	$ 1,351
2021 Convertible Senior Notes
Debt Instrument [Line Items]
Discount, beneficial conversion features	$ 29,866
2021 Convertible Senior Notes | Senior Notes
Debt Instrument [Line Items]
Principal	$ 100,000	102,900
Discount, original issuance		(28,321)
Unamortized debt issuance costs		(2,790)
Discount, beneficial conversion features		12,359
Convertible notes payable, net		$ 84,148

Convertible Notes Payable - Leg

Convertible Notes Payable - Legacy Narrative (Details)	Nov. 16, 2020USD ($)$ / sharesshares	May 31, 2019USD ($)$ / shares	May 31, 2019USD ($)$ / shares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2021USD ($)grant	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)$ / shares	Sep. 30, 2021	Nov. 15, 2020USD ($)	Aug. 01, 2019	Jun. 01, 2019
Debt Instrument [Line Items]
Loss on extinguishment of convertible notes - related party					$ 1,273,000	$ 0	$ (6,111,000)
Aggregate cash proceeds					100,000,000	9,009,000	19,346,000
Embedded derivative liability, initial fair value				$ 1,145,000		411,000	1,145,000
Embedded derivative assets, initial fair value				181,000			181,000
Derivative liability, current				$ 1,681,000	0		1,681,000
Change in fair value, embedded derivative					17,507,000	2,092,000	(716,000)
Annual effective interest rates in excess								14.30%
Accreted interest on convertible notes payable – related party					1,545,000	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
Payment made for debt issuance cost					$ 4,370,000	$ 0	$ 0
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					2
Aggregate cash proceeds					$ 10,768,000
Discount, fair value of preferred units					3,790,000				$ 3,790,000
Convertible Debt | 2019 Phase I Notes
Debt Instrument [Line Items]
Aggregate principal amount		$ 13,529,000	$ 13,529,000
Conversion ratio			1.15
Conversion price per unit (in usd per share) | $ / shares		$ 1.75	$ 1.75
Liquidation ratio		1.5	1.5							3	2
Optional prepayment ratio		3	3
Aggregate gross equity proceeds threshold		$ 25,000,000	$ 25,000,000
Percentage of holders for repayment to become due on demand		25.00%
Loss on extinguishment of convertible notes - related party				0
Redemption percentage		100.00%
Discount, fair value of preferred units						0
Annual effective interest rates in excess		400.00%	400.00%
Convertible Debt | 2019 Phase II Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 5,995,000			$ 5,995,000
Conversion ratio				1.15
Conversion price per unit (in usd per share) | $ / shares				$ 0.50			$ 0.50
Liquidation ratio				6			6
Percentage of holders for repayment to become due on demand				25.00%
Redemption percentage				200.00%
Aggregate cash proceeds						11,991,000
Discount, fair value of preferred units				$ 2,031,000		$ 2,031,000	$ 2,031,000
Annual effective interest rates in excess						1200.00%
Convertible Debt | 2020 Phase II Notes
Debt Instrument [Line Items]
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					$ 0
Convertible Debt | 2019 Convertible Notes
Debt Instrument [Line Items]
Debt instruments, coupon rate						0.00%
Convertible Debt | AltEnergy | Investor | 2019 Phase I Notes
Debt Instrument [Line Items]
Aggregate principal amount		$ 4,137,000	$ 4,137,000
Convertible Debt | AltEnergy | Investor | 2019 Phase II Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 2,017,000			$ 2,017,000
Convertible Debt | AltEnergy | Investor | 2020 Phase II Notes
Debt Instrument [Line Items]
Aggregate principal amount									$ 1,075,000

Convertible Notes Payable - Sum

Convertible Notes Payable - Summary of Balances Recognized upon Issuance of Convertible Notes (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Nov. 15, 2020	Dec. 31, 2019	May 31, 2019
Debt Instrument [Line Items]
Convertible notes payable, net	$ 6,371,000	$ 1,351,000
Convertible Debt
Debt Instrument [Line Items]
Convertible notes payable	108,863,000		$ 108,863,000
Discount, original issuance	(66,464,000)		(66,464,000)
Premium (Discount), embedded derivative	(1,375,000)		(1,375,000)
Discount, fair value of preferred units	(3,790,000)		(3,790,000)
Discount, beneficial conversion features	(1,799,000)		(1,799,000)
Convertible notes payable, net, excluding gross discount	35,435,000
Discount, accumulated amortization			73,428,000
Convertible notes payable, net			108,863,000
Principal		5,469,000		$ 19,524,000
Convertible Debt | 2019 Phase I Notes
Debt Instrument [Line Items]
Convertible notes payable		40,587,000
Discount, original issuance		(20,946,000)
Premium (Discount), embedded derivative		181,000
Discount, fair value of preferred units		0
Discount, beneficial conversion features		(1,799,000)
Convertible notes payable, net, excluding gross discount		18,023,000
Principal					$ 13,529,000
Convertible Debt | 2019 Phase II Notes
Debt Instrument [Line Items]
Convertible notes payable		35,973,000
Discount, original issuance		(23,982,000)
Premium (Discount), embedded derivative		(1,145,000)
Discount, fair value of preferred units		(2,031,000)		(2,031,000)
Discount, beneficial conversion features		0
Convertible notes payable, net, excluding gross discount		$ 8,815,000
Principal				$ 5,995,000
Convertible Debt | 2020 Phase I Notes
Debt Instrument [Line Items]
Convertible notes payable	510,000
Discount, original issuance	(340,000)
Premium (Discount), embedded derivative	0
Discount, fair value of preferred units	0
Discount, beneficial conversion features	0
Convertible notes payable, net, excluding gross discount	170,000
Convertible Debt | 2020 Phase II Notes
Debt Instrument [Line Items]
Convertible notes payable	31,793,000
Discount, original issuance	(21,196,000)
Premium (Discount), embedded derivative	(411,000)
Discount, fair value of preferred units	(1,759,000)
Discount, beneficial conversion features	0
Convertible notes payable, net, excluding gross discount	$ 8,427,000
Convertible Debt | Phase 1
Debt Instrument [Line Items]
Convertible notes payable			41,097,000
Discount, original issuance			(21,286,000)
Premium (Discount), embedded derivative			181,000
Discount, fair value of preferred units			0
Discount, beneficial conversion features			(1,799,000)
Discount, accumulated amortization			22,904,000
Convertible notes payable, net			41,097,000
Convertible Debt | Phase 2
Debt Instrument [Line Items]
Convertible notes payable			67,766,000
Discount, original issuance			(45,178,000)
Premium (Discount), embedded derivative			(1,556,000)
Discount, fair value of preferred units			(3,790,000)
Discount, beneficial conversion features			0
Discount, accumulated amortization			50,524,000
Convertible notes payable, net			$ 67,766,000

Notes Payable (Details)

Notes Payable (Details) - USD ($) $ in Thousands	Apr. 09, 2021	May 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Amount due at closing			$ 160	$ 0	$ 0
Long-term debt, current portion			1,644	924
Long-term debt			4,727	$ 427
Hi-Power Purchase Agreement | Notes Payable
Debt Instrument [Line Items]
Long-term debt, current portion			4,926
Long-term debt			$ 13,769
Hi-Power
Debt Instrument [Line Items]
Aggregate purchase price	$ 25,000
Amount due at closing		$ 5,000

Long-term Debt - Summary of Lon

Long-term Debt - Summary of Long-term Indebtedness (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 08, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Aggregate carrying value	$ 6,371		$ 1,351
Less: long-term debt, current portion	(1,644)		(924)
Long-term debt	4,727		427
Paycheck Protection Program
Debt Instrument [Line Items]
Aggregate carrying value	0	$ 1,273	1,257
Equipment financing facility
Debt Instrument [Line Items]
Aggregate carrying value	6,371		0
Other
Debt Instrument [Line Items]
Aggregate carrying value	$ 0		$ 94

Long-term debt - Narrative (Det

Long-term debt - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 07, 2020
Debt Instrument [Line Items]
Gain on debt forgiveness		$ 1,273,000	$ 0	$ 0
Long-term debt, current portion		1,644,000	924,000
Long-term debt		4,727,000	427,000
Debt issuance costs, gross	$ 175,000
Prepaid expenses		2,595,000	2,274,000
Line of credit facility, interest rate	3.25%
Repayment of equipment financing facility	$ 204,000	455,000	0	0
Debt instrument, fee amount	$ 70,000
Annual effective interest rates in excess	14.30%
Interest expense, debt		$ 1,545,000	$ 23,706,000	$ 49,708,000
Paycheck Protection Program
Debt Instrument [Line Items]
Principal					$ 1,257,000
Equipment financing facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 25,000,000
Long-term line of credit	7,000,000
Remaining borrowing capacity	18,000,000
Proceeds from lines of credit	500,000
Commitment fee amount	188,000
Debt issuance costs, gross	53,000
Prepaid expenses	$ 135,000
Non-utilization fee, percentage		3.00%
Line of credit, current		$ 1,644,000
Interest expense, debt		$ 157,000

Contingently Redeemable Prefe_3

Contingently Redeemable Preferred Units - Narratives (Details)	Nov. 16, 2020shares	Dec. 31, 2019USD ($)$ / sharesshares	Nov. 16, 2020USD ($)shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)$ / sharesshares
Temporary Equity [Line Items]
Debt threshold requiring preferred members majority vote | $				$ 1,000,000,000
Percentage deviated from approved budget requiring preferred members majority vote				15.00%
Liquidation preference, percentage				8.00%
Percentage threshold of voting units owned				50.00%
Liquidation preference | $		$ 136,816,000			$ 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
Unrecognized deemed dividend | $		$ 0
EES common units to be issued upon conversion (in shares) | shares					224,900,000
Series C Preferred Units
Temporary Equity [Line Items]
Preferred units issued (in usd per share)		$ 1.10		$ 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	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	$ 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 Prefe_4

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

Warrants Liability (Details)

Warrants Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class of Warrant or Right [Line Items]
Warrant outstanding (in shares)	7,002,254	8,750,000
Warrants liability - related party	$ 926	$ 2,701
Change in fair value, warrants liability - related party	$ (1,775)	$ 2,142	$ 0
Private Placement
Class of Warrant or Right [Line Items]
Warrant outstanding (in shares)	325,000

Stock-Based Compensation - Narr

Stock-Based Compensation - Narratives (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	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)	2,282,906	3,825,176
Expected life (years)	4 years 2 months 4 days	5 years 2 months 8 days	6 years 3 months
Unrecognized stock compensation expense	$ 31,487
Unrecognized stock compensation expense attributable to stock option	$ 3,507
Weighted average grant date fair value of options granted (in usd per share)	$ 8.08	$ 5.38	$ 1.21
Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting term	4 years
Options, vested and expected to vest, outstanding, number (in shares)	51,873
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
Expected life (years)	5 years
Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting term	5 years
Expected life (years)	10 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock compensation expense attributable to RUs	$ 27,980
Period for unrecognized stock compensation expense to be recognized	4 years
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
Number of additional shares authorized (in shares)	498,021

Stock-Based Compensation - Comp

Stock-Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 15,058	$ 5,081	$ 135
Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	3,809	4,104	131
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 11,249	$ 977	$ 4

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Beginning outstanding balance (in shares)	2,143,636	392,838	303,028
Granted (in shares)	114,429	1,972,679	254,882
Cancelled/Forfeited (in shares)	(110,768)	(221,881)	(165,072)
Exercised (in shares)	(123,837)
Ending outstanding balance (in shares)	2,023,460	2,143,636	392,838	303,028
Exercisable (in shares)	1,124,199
Weighted-Average Exercise Price
Beginning outstanding balance (in usd per share)	$ 9.19	$ 15.09	$ 26.20
Granted (in usd per share)	18.07	9.07	9.54
Cancelled/Forfeited (in usd per share)	13.02	18.57	27.24
Exercised	8.67
Ending outstanding balance (in usd per share)	9.51	$ 9.19	$ 15.09	$ 26.20
Exercisable (in usd per share)	$ 9.55
Weighted-Average Remaining Contractual Term (years)
Options outstanding	6 years 3 months 18 days	9 years 6 months	5 years 4 months 24 days	2 years 9 months 18 days
Options exercisable	7 years

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Unit Activity (Details) - RSUs	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Units
RU Outstanding, beginning balance (in shares) | shares	42,318
Granted in period (in shares) | shares	2,580,670
Cancelled/Forfeited in period (in shares) | shares	(273,632)
Vested in period (in shares) | shares	(154,600)
RU Outstanding, ending balance (in shares) | shares	2,194,756
Weighted-Average Grant-Date Fair Value
Period start RU outstanding weighted average fair value (in usd per share) | $ / shares	$ 13.46
Granted, weighted-average grant-date fair value (in usd per share) | $ / shares	16.62
Cancelled/Forfeited, weighted-average grant-date fair value (in usd per share) | $ / shares	14.98
Vested, weighted-average grant-date fair value (in usd per share) | $ / shares	16.50
Period end RU outstanding weighted average fair value (in usd per share) | $ / shares	$ 16.36

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-Average Assumptions Used to Determine the Fair Value of Options Granted (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Volatility	58.86%	52.99%	58.20%
Risk free interest rate	0.67%	0.39%	1.89%
Expected life (years)	4 years 2 months 4 days	5 years 2 months 8 days	6 years 3 months
Dividend yield	0.00%	0.00%	0.00%

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2021
Leases [Abstract]
Operating lease right-of-use asset, net	$ 3,468	$ 0		$ 3,662
Present value of minimum lease payments	4,308			$ 4,465
Operating lease, cost	$ 1,158	$ 959	$ 1,291
Operating lease, weighted average remaining lease term	4 years 1 month 24 days
Operating lease, weighted average discount rate, percent	3.30%
Finance lease, weighted average remaining lease term	3 years 5 months 19 days
Finance lease, weighted average discount rate, percent	12.50%
Sales-type lease, term of contract	20 years
Sales-type lease, interest income, lease receivable	$ 353
Sales-type lease, lease receivable	$ 347

Leases - Balance Sheet Classifi

Leases - Balance Sheet Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease right-of-use asset, net	$ 3,468	$ 3,662	$ 0
Finance lease assets	28
Total lease assets	3,496
Liabilities
Operating lease liability, current portion	1,084		0
Finance lease liability	8
Operating lease liability, long-term	3,224		$ 0
Finance lease liability	17
Present value of minimum lease payments	$ 4,333
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Property and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other liabilities

Leases - Future Minimum Lease (

Leases - Future Minimum Lease (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Jan. 01, 2021
Operating lease
2022	$ 1,210
2023	850
2024	916
2025	986
2026	601
Later years	0
Later years	0
Total minimum lease payments	4,563
Less amounts representing interest	255
Present value of minimum lease payments	4,308	$ 4,465
Financing lease
2022	12
2023	8
2024	8
2025	8
2026	1
Later years	37
Less amounts representing interest	12
Present value of minimum lease payments	25
Total
2022	1,222
2023	858
2024	924
2025	994
2026	602
Later years	0
Total minimum lease payments	4,600
Less amounts representing interest	267
Present value of minimum lease payments	$ 4,333

Leases - Future Minimum Lease P

Leases - Future Minimum Lease PY (Details) $ in Thousands	Dec. 31, 2020USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2021	$ 685
2022	755
2023	825
2024	895
2025	966
Later years	679
Total minimum lease payments	4,805
Capital
2022	14
2023	4
2024	0
2025	0
2026	0
Later years	0
Total minimum lease payments	18
Less amounts representing interest	3
Present value of minimum lease payments	$ 15

Fair Value Measurement - Fair V

Fair Value Measurement - Fair Value of Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private Placement Warrants	$ 926	$ 2,701
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private Placement Warrants	0	0
Fair Value, Inputs, Level 1 | Embedded Derivative Financial Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative liability within the 2021 Convertible Notes	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private Placement Warrants	926	2,701
Fair Value, Inputs, Level 2 | Embedded Derivative Financial Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative liability within the 2021 Convertible Notes	0	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private Placement Warrants	0	0
Fair Value, Inputs, Level 3 | Embedded Derivative Financial Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative liability within the 2021 Convertible Notes	$ 12,359	$ 0

Fair Value Measurement - Carryi

Fair Value Measurement - Carrying Value and Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Carrying Value | Notes Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	$ 18,695	$ 0
Carrying Value | Equipment financing facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	6,370	0
Carrying Value | 2021 Convertible Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	71,789	0
Carrying Value | Paycheck Protection Program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	0	1,257
Fair Value | Fair Value, Inputs, Level 3 | Notes Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	14,607	0
Fair Value | Fair Value, Inputs, Level 3 | Equipment financing facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	5,951	0
Fair Value | Fair Value, Inputs, Level 3 | 2021 Convertible Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	61,866	0
Fair Value | Fair Value, Inputs, Level 2 | Paycheck Protection Program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument	$ 0	$ 1,222

Fair Value Measurement - Liabil

Fair Value Measurement - Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ 12,359	$ 0	$ 1,681
Additions	29,866	411
Change in fair value included in earnings	(17,507)	(2,092)
Balance at end of the period	$ 12,359	$ 0

Shareholders' Equity (Details)

Shareholders' Equity (Details) $ / shares in Units, $ in Thousands	Jan. 22, 2021tradingDay$ / sharesshares	Nov. 16, 2020tradingDay$ / sharesshares	Dec. 31, 2021USD ($)vote$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	May 22, 2020$ / sharesshares
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)		2,000,000	53,786,632	48,943,082
Common stock, shares outstanding (in shares)			53,786,632	48,943,082
Contingent equity, earnout period		5 years
Contingent equity, earnout period, threshold business days | tradingDay		5
Contingent equity, earnout period, threshold price (in usd per share) | $ / shares	$ 16	$ 16
Contingent equity, earnout period, threshold trading days | tradingDay	20	20
Contingent equity, earnout period, threshold consecutive trading days | tradingDay	30	30
Contingent consideration, liability (in shares)		1,718,000
Contingent consideration, liability, earnout period		5 years
Contingent liability, earnout period, threshold trading days | tradingDay	20	20
Contingent liability, earnout period, threshold consecutive trading days | tradingDay	30	30
Cancellation of shares used to settle payroll tax withholding | $			$ 353
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)			7,002,254	8,750,000
Issuance of contingently issuable common stock (in shares)			0
Capital contribution - disgorgement of short swing profits | $				$ 432
Related party, ownership interest qualifier			5.00%
B. Riley Financial Inc.
Class of Stock [Line Items]
Related party, ownership interest qualifier				5.00%
Block A Sponsor Earnout Shares
Class of Stock [Line Items]
Contingent consideration, liability (in shares)		859,000
Stock price trigger | $ / shares		$ 12
Block B Sponsor Earnout Shares
Class of Stock [Line Items]
Contingent consideration, liability (in shares)		859,000
Stock price trigger | $ / shares	$ 16	$ 16
Common Stock
Class of Stock [Line Items]
Issuance of contingently issuable common stock (in shares)	1,999,185		1,999,185
Exercise of public warrants (in shares)			1,747,746
Additional Paid in capital
Class of Stock [Line Items]
Cancellation of shares used to settle payroll tax withholding | $			$ 353
Capital contribution - disgorgement of short swing profits | $				$ 432

Shareholders' Equity - Anti-dil

Shareholders' Equity - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock options and restricted stock units
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	4,218,216	2,185,954	392,838
Warrants
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	7,327,254	9,075,000	0
Block B Sponsor Earnout Shares subject to restrictions
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	0	859,000	0
Contingently Issuable Common Stock
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	0	2,000,000	0
Convertible Notes (if converted)
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	5,144,074	0	7,655,908
Contingent redeemable preferred units
Class of Stock [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	0	0	12,964,231