Alliant Energy: Wisconsin Power and Light Company files request to change retail electric and natural gas rates

Media Contact: Rob Crain (608) 458-4469

Investor Relations: Jamie Freeman (608) 458-3274

MADISON, WI – May 8, 2009 – Wisconsin Power and Light Company (WPL), a subsidiary of Alliant Energy Corporation (NSYE: LNT), filed a request today with the Public Service Commission of Wisconsin (PSCW) to adjust its retail electric and natural gas rates, effective January 1, 2010. WPL is requesting to increase retail electric rates by $85.5 million (9.2 percent) and increase natural gas service rates by $6.2 million (2.6 percent), when compared to current rates. The impact of the proposed change in rates will vary depending on customer class.

The request seeks to recover costs of operating the electric and natural gas utility systems. Such cost recovery has been severely reduced by a material reduction in sales and increased costs. Among the increased costs are those associated with providing utility service and investments related to maintaining a safe and reliable electric and gas infrastructure, enhancing renewable energy resources, promoting environmental stewardship via environmental control projects and providing additional energy-efficiency initiatives and options for customers. WPL’s increased electric costs have been partially offset by recent decreases in electric fuel costs.

“Recognizing the challenging economic situation for our customers, we made the decision to not increase our rates during 2009; however, an increase is needed in 2010 to maintain a reliable electric and gas system and stay financially strong to allow us to provide ongoing utility services,” said Barbara J. Swan, President-WPL. “We are dedicated to controlling our operational costs and have taken many steps to do so, while at the same time realizing that we are obligated to serve and need to recover our fixed costs and lay the groundwork for the future in terms of environmental, energy efficiency and renewable investments.

“We know that even though our investments to maintain quality service benefit our customers over the long run, there is also an impact on their monthly bills. We understand that our customers face difficult financial choices in the midst of this economic downturn. We encourage our customers to take advantage of the number of programs Focus on Energy and our company offer to help customers manage their energy costs.”

Alliant Energy is currently putting together specific data on how the rate case filing will impact all customer classes – residential, commercial, industrial, and agricultural – a process known as “rate design”. The rate design information will be filed with the PSCW by June 1st and the average monthly dollar impact on customers will be available at that time. The actual amount may vary depending on the outcome of the pending case and associated rate designs approved by the Commission.

The approval process for the base rate case is expected to take approximately seven months, resulting in new rates becoming effective on or about January 1, 2010. The electric and gas rate request is based on forecasted costs for 2010. All rate changes must be approved by the PSCW after a thorough review of the data and after obtaining input from the public.

Additional information for customers on the rate case and energy-saving ways to reduce the impact of the proposed rate changes is available at http://www.alliantenergy.com/wisconsinrates.