Wisconsin Power and Light Receives Public Service Commission of Wisconsin Approval to Purchase Neenah Generating Facility

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

MADISON, Wis., April 11 /PRNewswire-FirstCall/ — Wisconsin Power and Light Company (WPL), a subsidiary of Alliant Energy Corporation (NYSE:LNT) , has received approval from the Public Service Commission of Wisconsin to purchase the Neenah Generating Facility, an existing 300 megawatt, simple cycle, natural gas-fired electric generating facility located in the Town of Neenah, Wisconsin. This purchase is intended to replace the output currently obtained under a purchased power agreement (PPA) with Calpine’s RockGen Facility.

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“This purchase represents the lowest-cost option to meet our customers’ long-term peaking power needs,” said Barbara Swan, President of WPL. “Demand continues to increase throughout our WPL service territory, and having the ability to meet that demand in a cost-effective manner is crucial.”

Peaking power units are traditionally gas-fired combustion turbines that are utilized to meet customer’s 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 this an excellent resource for responding to peak demands. The natural gas unit would further broaden WPL’s existing fuel mix.

The Neenah Generating Facility is currently owned by Alliant Energy Resources (AER), a non-regulated affiliate of WPL, and began commercial operation in 2000. WPL needs approval from the Federal Energy Regulatory Commission. WPL plans to purchase the facility, pending federal regulatory approval, for the net book value of the plant, which is expected to be approximately $95 million. The purchase is expected to occur in June, 2009 upon the expiration of the RockGen PPA.

Alliant Energy is an energy-services provider with subsidiaries serving approximately 1 million electric and over 400,000 natural gas customers. Providing its customers in the Midwest with regulated electric and natural gas service is the company’s primary focus. Wisconsin Power and Light, the company’s Wisconsin utility subsidiary, serves 453,000 electric and 175,000 natural gas customers. Alliant Energy, headquartered in Madison, Wis., is a Fortune 1000 company traded on the New York Stock Exchange under the symbol LNT. For more information, visit the company’s Web site at http://www.alliantenergy.com/.

This press release includes forward-looking statements. These forward- looking statements can be identified as such because the statements include words such as “expected,” “plans” or other words of similar import. Such statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those currently anticipated. Actual results could be affected by such factors as: regulatory actions or legal proceedings which delay, prevent or alter the proposed terms of the purchase, including inability to obtain all necessary approvals; unforeseen events which cause the book value of the plant to change; unanticipated issues related to the Calpine bankruptcy; and economic conditions in WPL’s service territory. These factors should be considered when evaluating the forward- looking statements and undue reliance should not be placed on such statements. The forward- looking statements included herein are made as of the date hereof and Alliant Energy and WPL undertake no obligation to update publicly such statements to reflect subsequent events or circumstances.

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Source: Alliant Energy Corporation

CONTACT: media, Rob Crain, +1-608-458-4469, or investors, Jamie Freeman,
+1-608-458-3274, both for Alliant Energy Corporation

Web site: http://www.alliantenergy.com/