Exhibit 99.1 Alliant Energy Corporation Corporate Headquarters 4902 North Biltmore Lane Madison, WI 53718-2148 www.alliantenergy.com News Release FOR IMMEDIATE RELEASE Media Hotline: (608) 458-4040 Investor Relations: Susan Gille (608) 458-3956 ALLIANT ENERGY ANNOUNCES FIRST QUARTER 2024 RESULTS • First quarter GAAP earnings per share was $0.62 in 2024, compared to$0.65 in 2023 • Reaffirming 2024 earnings guidance range of $2.99 -$3.13 per share MADISON, Wis. - May 2, 2024 - Alliant Energy Corporation (NA ...