Cover - shares	9 Months Ended
	Sep. 30, 2022	Oct. 31, 2022
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	001-39525
Entity Registrant Name	ESS Tech, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-1550150
Entity Address, Address Line One	26440 SW Parkway Ave.
Entity Address, Address Line Two	Bldg. 83
Entity Address, City or Town	Wilsonville
Entity Address, State or Province	OR
Entity Address, Postal Zip Code	97070
City Area Code	855
Local Phone Number	423-9920
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		153,258,791
Entity Central Index Key	0001819438
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common stock, $0.0001 par value per share
Trading Symbol	GWH
Security Exchange Name	NYSE
Common Stock Warrants
Entity Information [Line Items]
Title of 12(b) Security	Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $11.50
Trading Symbol	GWH.W
Security Exchange Name	NYSE