Cover Page - shares	9 Months Ended
	Sep. 30, 2025	Nov. 07, 2025
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2025
Document Transition Report	false
Entity File Number	001-40272
Entity Registrant Name	OPAL FUELS INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-1578357
Entity Address, Address Line One	One North Lexington Avenue
Entity Address, Address Line Two	Suite 1450
Entity Address, City or Town	White Plains
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10601
City Area Code	914
Local Phone Number	705-4000
Title of 12(b) Security	Class A Common Stock, par value $0.0001 per share
Trading Symbol	OPAL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Central Index Key	0001842279
Amendment Flag	false
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		28,996,177
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		121,500,000
Class D Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		22,899,037