v3.26.1
Cover Page - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 16, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
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 Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
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    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 65,017,000
Documents Incorporated by Reference The information required by Part III of Form 10‑K is incorporated herein by reference to portions of the registrant’s Definitive Proxy Statement relating to its 2026 Annual General Meeting of Shareholders, which will be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2025    
Entity Central Index Key 0001842279    
Amendment Flag false    
Document FY Focus 2025    
Document Fiscal Period Focus FY    
Common Class A      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   29,001,120  
Common Class B      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   121,500,000  
Common Class D      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   22,899,037