Recent Press Release

Interstate Power and Light Company files Sutherland Generating Station Unit 4 advanced ratemaking principles application with Iowa Utilities Board

Application demonstrates that proposed facility is the most reasonable and cost-effective option for customers

CEDAR RAPIDS, Iowa – March 31, 2008 – Interstate Power and Light Company (IPL), a subsidiary of Alliant Energy Corporation (NYSE: LNT), filed with the Iowa Utilities Board (IUB) today an application for advanced ratemaking principles concerning IPL’s proposed construction of the Sutherland Generating Station Unit 4, located in Marshalltown, Iowa.

“Construction of Sutherland Generating Station Unit 4 is the right choice for our customers, economy and environment,” says Tom Aller, president of IPL. “We believe the decision to construct and operate Sutherland Generating Station Unit 4 is the most reasonable and cost-effective option for our customers as it reduces exposure to volatile purchased power markets. We expect that construction of the facility will bolster Iowa’s economy with more than 1,400 on-site construction jobs and a project payroll of approximately $343 million. Upon completion, the power plant expects to employ more than 85 employees with an annual operational payroll of approximately $8.5 million.”

In addition, an economic development impact analysis recently completed indicates that the facility could support the growth of 105,000 Iowa jobs with a total labor payroll of approximately $3.65 billion.

Iowa statute requires the IUB to issue a ruling on ratemaking principles that are to be applicable for any baseload generating facility over 300 megawatts. Ratemaking principles define how construction costs will be recovered in utility rates throughout the life of the generating facility. IPL is requesting a 12.55 percent return on common equity as part of the filing.

IPL expects to receive an IUB decision on its application for ratemaking principles for Sutherland Generating Station Unit 4 in the third quarter of 2008.

IPL filed Sutherland Generating Station Unit 4’s siting application for the project in July 2007. IPL expects a decision from the IUB on this application in May 2008. Approval of both the siting application and ratemaking principles application are necessary before construction begins.

IPL is requesting that the ratemaking principles apply to up to 432.5 megawatts of the proposed 649 megawatt facility. IPL will own 350 megawatts of the facility’s output. Central Iowa Power Cooperative and Corn Belt Power Cooperative will each receive 100 megawatts of output. North Iowa Municipal Electric Cooperative Association’s participating municipal members will receive approximately 16.5 megawatts. IPL expects to attain additional partners or enter into purchased power agreements for the remaining 82.5 megawatts of capacity above its previously announced planned 350 megawatt share.

IPL expects its total cost in escalated dollars for the company’s 350 megawatt share of the facility, excluding allowance for funds used during construction, to be approximately $950 million to $1,050 million.

As announced in February 2008, IPL’s advanced ratemaking principles application includes details on the company’s stated plans to permanently reduce greenhouse gas emissions when the proposed Sutherland Generating Station Unit 4 becomes operable in 2013. IPL’s proposal includes the retirement or fuel switching of less efficient coal-fired generating stations, aggressively pursuing energy efficiency and investing in renewables. Combined, IPL expects its plan will more than offset its 350 megawatt ownership share of Sutherland Generating Station Unit 4’s expected CO2 emissions in 2013 when the facility is operational.

“Sutherland Generating Station Unit 4 will enable our company to permanently reduce carbon dioxide emissions,” adds Mr. Aller. “With an obligation to serve, it is critical that our company pursue a long-term plan that balances the need to meet growing energy demand and strengthen Iowa’s economy with mitigating the impact to our environment. The proposal filed today provides a balanced approach to positioning Iowa for a bright energy future.”

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. The power plant is a 630 megawatt facility with an additional 19 megawatt equivalent of steam cogeneration that will be available for use by nearby industries.

This press release includes forward-looking statements. These forward- looking statements can be identified as such because the statements include words such as “expects,” “believe,” “approximately,” 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; political conditions in IPL's service territories; failure of equipment and technology to perform as expected; unsuccessful negotiations with potential utility partners for co-ownership or purchased power arrangements; inability to find additional partners; 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: Ryan Stensland (319) 786-4171
Investor Relations: Jamie Freeman (608) 458-3274