The Riverside Energy Center, a subsidiary of Calpine Corp, is a 600MW combined cycle natural gas-fired electric generating facility located in Beloit, Wisconsin, and it began operation in 2004.

WPL currently has a purchase power agreement with Riverside for about 500MW.

Under the purchase power agreement, WPL has the option to purchase Riverside if it exercises the option on or before 31 May 2012.

WPL will make a decision whether to exercise its option to purchase Riverside on or before 31 May 2012, and if the company does exercise its option, closing is expected to occur by 31 December 2012.