Recent Press Release

Interstate Power and Light Company receives pre-certification approval for construction of proposed Sutherland Generating Station Unit 4

DES MOINES, Iowa – April 30, 2008 – Interstate Power and Light Company (IPL), a subsidiary of Alliant Energy Corporation (NYSE: LNT), received pre-certification approval today from the Iowa Utilities Board (IUB) for construction of the company’s proposed Sutherland Generating Station Unit 4, located in Marshalltown, Iowa.

In its oral decision, the IUB approved IPL’s Application for Generation Siting Certificate (Siting Certification) on the conditions that IPL would periodically review the viability of carbon capture and sequestration technology for the proposed power plant with the IUB; the facility would utilize switch grass, corn stalks or other similar agriculturally based products for five and ten percent, respectively, of its fuel source within two and five years, respectively, of the facility becoming operational; ten percent of the company’s energy would be derived from renewables by 2013 and IPL would increase the amount of renewables in its energy portfolio by one percent per year for 15 years after the Sutherland Generating Station Unit 4 becomes operational.

The IUB expects to issue its written order within the next several weeks. The written order will provide additional details concerning the decision.

“Today’s decision moves forward the process of constructing and operating Sutherland Generating Station Unit 4,” stated Tom Aller, President-IPL. “Through the construction of Sutherland Generating Station Unit Four, our company is pleased to support Iowa’s economy by providing new Iowa-based sources of safe, reliable and environmentally responsible energy. The continued support IPL has received from its partners, labor representatives and residents and business leaders in Marshalltown and across our service area for this project has been overwhelming.”

The IUB’s decision to grant certification for construction of the proposed Sutherland Generating Station Unit 4 is also contingent upon IPL receiving all necessary permits and regulatory approvals related to the proposed power plant project. There are two required approvals, including the company’s air permit application and approval of advanced ratemaking principles, remaining before construction of Sutherland Generating Station Unit 4 begins. IPL expects to receive a decision from the Iowa Department of Natural Resources on its air quality permit application by the end of the third quarter 2008. The company also expects to receive a decision from the IUB on its request for advanced ratemaking principles in the third quarter 2008. The company expects to begin construction by the end of 2008 and expects the facility to be operational in 2013.

“We remain strongly committed toward making Sutherland Generating Station Unit Four a reality for the benefit of all Iowans,” added Aller. “While we are awaiting the IUB’s written order in the coming weeks, the conditions set forth in today’s decision appear to be reasonable and attainable.”

Sutherland Generating Station Unit 4 is a 630 megawatt facility with an additional 19 megawatt equivalent of steam cogeneration that will be available for use by nearby industries. The power plant’s design consists of a hybrid technology, which allows the facility to utilize switch grass, corn stalks or other similar agriculturally based products for up to 10 percent of its fuel source. As a result, IPL expects to reduce the amount of coal burned at the facility.

This statement contains forward-looking statements. These forward- looking statements can be identified as such because the statements include words such as "expects," or other words of similar import. Similarly, statements that describe future plans or strategies are also forward-looking statements. 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: state or federal regulatory actions or local government actions, including inability to obtain all necessary approvals and permits; unanticipated construction issues, delays or expenditures; current or future litigation, regulatory investigations, proceedings or inquiries that could impede the implementation of the IPL's plans; failure of equipment and technology to perform as expected; unsuccessful negotiations with potential partners for co-ownership or purchased power arrangements; inability to find additional partners; political conditions in IPL's service territories; and economic conditions in IPL'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 IPL undertake no obligation to update publicly such statements to reflect subsequent events or circumstances.

Media Contact: Rob Crain (608) 458-4469
Investor Relations Contact: Jamie Freeman (608) 458-3274