Exhibit 99.1 Talen Energy Reports First Quarter 2026 Results, Reaffirms 2026 Guidance Earnings Release Highlights HOUSTON, May 5, 2026 – Talen Energy Corporation ("Talen," the "Company," "we," or "our") (NASDAQ: TLN), a leading independent power producer, today reported its first quarter 2026 financial results and other highlights. "Talen started the year strong and today we are reporting first quarter results, earning $473 million of Adjusted EBITDA and $350 million of Adjusted Free Cash Flow. We continue ...