Recent Press Release

Wisconsin Power and Light Company's Second Nature Program Receives Green-e Certification

Madison, Wis. - April 19, 2007 - Wisconsin Power and Light Company (WP&L), an Alliant Energy Company (NYSE: LNT), announced today that its Second Nature renewable energy program has received Green-e certification from the Center for Resource Solutions (CRS), a national, nonprofit organization which certifies renewable power products sold by marketers, utilities and energy service providers in wholesale and retail markets.

Second Nature, a voluntary program through which Alliant Energy customers support renewable energy equivalent to a portion of their monthly electric usage, currently has more than 13,000 residential and business participants. The Second Nature program at Alliant Energy's Iowa-based utility, Interstate Power and Light Co., has been Green-e certified since 2004.

“We're very pleased to add our Second Nature program in Wisconsin to the Green-e status,” said Janice Mathis, product manager, Second Nature. “As the early adopters of renewable energy, all of our Second Nature customers now have the assurance that the renewable energy we purchase on their behalf meets the high standards established by CRS. We hope this achievement motivates more of our customers to join Second Nature and take advantage of the opportunity to reduce their carbon dioxide impact.”

Introduced in 2001, the Second Nature program purchases renewable energy from wind, solar and landfill sources. Over 42 million kilowatt-hours of renewable energy was purchased in 2006 on behalf of Second Nature customers.

“As we make decisions on how to meet the increasing demand for energy, our company's use of renewable energy will continue to grow,” said Kim Zuhlke, vice president-New Energy Resources. “Careful planning, as well as a commitment to balancing the needs of our customers and our environmental impact, makes renewable energy a solid choice.”

In addition to a semiannual compliance review, CRS also annually verifies all certified renewable power products to ensure that Green-e participants procured enough supply to meet their sales, resources and other requirements of the Green-e program.

“We are pleased that Alliant Energy now provides Green-e certified renewable electricity to its Wisconsin customers,” said Michael Vickerman, executive director of the renewable energy advocacy group RENEW Wisconsin. “More and more people are coming to understand that the health of the planet can be greatly affected by their energy decisions, and they want to do the right thing for the environment. Subscribing to a high-quality program like Second Nature is for many customers a simple yet powerful way to make sustainable energy a bigger part of everyday life.”

About Alliant Energy

Alliant Energy is an energy-services provider with subsidiaries serving approximately 1 million electric and over 420,000 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 456,000 electric and 182,000 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 www.alliantenergy.com.

About Green-e

Green-e provides an easy way for consumers to find credible greenhouse gas mitigation options that fit their budgets. The Green-e Program currently offers two types of certification: renewable energy product certification and certification of renewable energy commitments by businesses and organizations. Beginning in May, 2007, Green-e will also offer certification of retail greenhouse gas reduction products (or carbon offsets). Leadership in guiding renewable energy and climate change policies over the last 10 years have made Green-e the leading certification and verification program that sets standards and provides market support. To learn more about Green-e certified products and programs available in all 50 states, visit www.green-e.org. Green-e is a program of the Center for Resource Solutions (CRS), a national nonprofit organization that works to make it easier for people and organizations to mitigate climate change. CRS designs and operates national and international programs that support the increased supply and use of renewable energy resources, greenhouse gas reductions, and energy efficiency measures. To learn more about CRS, visit: www.resource-solutions.org.

Media Contact: Erin Dammen (608) 458-3285