Alliant Energy Corporation is a public utility holding company that incorporated in Madison, Wisconsin in 1981. It consists of four subsidiaries:
- Interstate Power and Light Company (IPL) is a public utility that generates and distributes electricity and distributes and transports natural gas in Iowa.
- Wisconsin Power and Light Company (WPL) provides similar services as IPL in southern and central Wisconsin.
- Resource is organized to manage non-regulated investments
- Corporate Services provides administrative services to Alliant Energy and its subsidiaries.