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Cover - USD ($)
 12 Months Ended
Dec. 31, 2025
Jan. 31, 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 001-15891    
Entity Registrant Name NRG Energy, Inc    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 41-1724239    
Entity Address, Address Line One 1301 McKinney Street    
Entity Address, City or Town Houston    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77010    
City Area Code 713    
Local Phone Number 537-3000    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 26,643,647,974
Entity Common Stock, Shares Outstanding   214,677,543  
Documents Incorporated by Reference
Portions of the Registrant's definitive Proxy Statement relating to its 2026 Annual Meeting of Stockholders
are incorporated by reference into Part III of this Annual Report on Form 10-K 		   
Entity Central Index Key 0001013871    
Amendment Flag false    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
New York Stock Exchange      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, par value $0.01    
Trading Symbol NRG    
Security Exchange Name NYSE    
NYSE Texas      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, par value $0.01    
Trading Symbol NRG    
Security Exchange Name NYSE