Wisconsin Power and Light: Closes on purchase of the Neenah Energy Facility

Media Contact: Rob Crain (608) 458-4469

Investor Relations: Jamie Freeman (608) 458-3274

Purchase will replace output previously obtained from purchased power agreement with RockGen Facility

Madison, WI – June 1, 2009 – Wisconsin Power and Light Company (WPL), a subsidiary of Alliant Energy Corporation (NYSE: LNT), closed on the purchase of the Neenah Energy Facility, an existing 300 megawatt, simple cycle, natural gas-fired electric generating facility located in the Town of Neenah, Wisconsin. This purchase will replace the output previously obtained through a purchased power agreement with Calpine’s RockGen facility, which terminated on May 31, 2009.

“This purchase represents the lowest-cost option to meet our customers’ long-term peaking power needs,” said Barbara Swan, President of WPL. “Having the ability to meet those needs in a cost-effective manner, while providing flexibility for the future, is crucial.”

Peaking power units are traditionally gas-fired combustion turbines that are utilized to meet customers’ needs for electricity on hot summer days when demand is highest. This type of combustion turbine can be started and shut down more quickly than coal-based units, thus affording more flexibility and making it an excellent resource for responding to peak demands. The natural gas unit will further broaden WPL’s existing fuel mix.

The Neenah Energy Facility was previously owned by Alliant Energy Resources, LLC, a non-regulated affiliate of WPL. The company received approvals from the Public Service Commission of Wisconsin in April 2008 and the Federal Energy Regulatory Commission in September of 2008 to purchase the facility. WPL is purchasing the facility for approximately $92 million, the net book value of the plant and related assets.