Exhibit 99.1 Contact: Media: Lena Funston (509) 495-8090 lena.funston@avistacorp.com Investors: Stacey Wenz (509) 495-2046 stacey.wenz@avistacorp.com Avista 24/7 Media Access (509) 495-4174 Avista Corp. Reports Financial Results for the First Quarter of 2024, Confirms 2024 Earnings Guidance • First quarter consolidated earnings per diluted share of $0.91, in line with expectations • Confirms consolidated earnings guidance of$2.36 to $2.56 per diluted share SPOKANE, Wash. – May 1, 2024, 4:05 a.m. PDT: Avist ...