The price was about $92 million.
The generating plant replaces the output currently obtained under a purchased power agreement with Calpine's RockGen Facility that terminated May 31.
"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."
The Neenah Generating Facility, which began operation in 2000, was owned by Alliant Energy Resources, a nonregulated affiliate of Wisconsin Power and Light. Wisconsin Power and Light is owned by Madison-based Alliant Energy Corp.