v3.26.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2025
Jun. 12, 2026
Jun. 30, 2025
Document Information [Line Items]      
Entity Central Index Key 0001883984    
Entity Registrant Name Alternus Clean Energy, Inc.    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2025    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Document Transition Report false    
Entity File Number 001-41306    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 87-1431377    
Entity Address, Address Line One 17 State Street, Suite 4000    
Entity Address, City or Town New York    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10004    
City Area Code 212    
Local Phone Number 739-0727    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status No    
Entity Interactive Data Current No    
Entity Filer Category Non-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     $ 1,650,000
Entity Common Stock, Shares Outstanding   724,658  
Auditor Firm ID 6651    
Auditor Name Kreit & Chiu CPA LLP    
Auditor Location Los Angeles, California    
Warrant [Member]      
Document Information [Line Items]      
Title of 12(b) Security Warrants, each whole warrant exercisable for one share of Common Stock    
Trading Symbol ACLEW    
Common Stock [Member]      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, par value $0.0001 per share    
Trading Symbol ALCE