Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Common Stock Warrants	Additional Paid-In Capital	Accumulated Deficit
Balance at beginning of period (in shares) at Dec. 31, 2020	0
Balance at beginning of period at Dec. 31, 2020	$ 0
Balance at end of period (in shares) at Mar. 31, 2021	0
Balance at end of period at Mar. 31, 2021	$ 0
Balance at beginning of period (in shares) at Dec. 31, 2020		58,919,345
Balance at beginning of period at Dec. 31, 2020	(27,888)	$ 6	$ 153	$ 35,446	$ (63,493)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Legacy ESS Redeemable Convertible Preferred Stock (in shares)		5,746,003
Issuance of Legacy ESS Redeemable Convertible Preferred Stock	29,516	$ 1		29,515
Issuance of common stock upon exercise of options (in shares)		2,379,260
Issuance of common stock upon exercise of options	518			518
Issuance of common stock upon exercise of warrants (in shares)		60,418
Issuance of common stock upon exercise of warrants	356			356
Stock-based compensation expense	129			129
Net loss	(154,918)
Balance at end of period (in shares) at Mar. 31, 2021		67,105,026
Balance at end of period at Mar. 31, 2021	$ (152,287)	$ 7	153	65,964	(218,411)
Balance at beginning of period (in shares) at Dec. 31, 2021	0
Balance at beginning of period at Dec. 31, 2021	$ 0
Balance at end of period (in shares) at Mar. 31, 2022	0
Balance at end of period at Mar. 31, 2022	$ 0
Balance at beginning of period (in shares) at Dec. 31, 2021		151,839,058
Balance at beginning of period at Dec. 31, 2021	$ 205,159	$ 16	0	745,753	(540,610)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)	138,617	138,617
Issuance of common stock upon exercise of options	$ 47			47
Issuance of common stock upon release of restricted stock units (in shares)		873,070
Cancellation of shares used to settle payroll tax withholding (in shares)		(244,202)
Cancellation of shares used to settle payroll tax withholding	(2,808)			(2,808)
Issuance of common stock upon exercise of warrants (in shares)		20
Stock-based compensation expense	2,760			2,760
Net loss	(5,709)				(5,709)
Balance at end of period (in shares) at Mar. 31, 2022		152,606,563
Balance at end of period at Mar. 31, 2022	$ 199,449	$ 16	$ 0	$ 745,752	$ (546,319)