Exhibit 99.1 NRG Energy, Inc. Reports First Quarter 2025 Results and Reaffirms 2025 Financial Guidance HOUSTON—May 12, 2025—NRG Energy, Inc. (NYSE: NRG) today reports GAAP Net Income of $750 million for the three months ended March 31, 2025. GAAP EPS — basic is$3.70, Cash Provided by Operating Activities is $855 million, Adjusted Net Income is$531 million, Adjusted EPS is $2.68, Adjusted EBITDA is$1,126 million, and Free Cash Flow before Growth Investments (FCFbG) is $293 million for the first quarter of ...