December 15, 2008 Cedar Ridge Wind Farm begins producing emissions-free energy

MADISON, WI – December 15, 2008
Wisconsin Power and Light Company (WPL), a subsidiary of Alliant
Energy Corporation (NYSE: LNT), has begun commercial operation of
Cedar Ridge Wind Farm, providing an additional 68 megawatts of
emissions-free wind energy for its customers.

This is an important day for Alliant Energy and our customers as we
continue to strive to meet the increasing demand for green energy,
said Bill Harvey, President and Chief Executive Officer for Alliant
Energy. The addition of Cedar Ridge to our renewable energy portfolio
moves us further down the path to a greener energy future.

Cedar Ridge consists of 41 wind turbines spread out over 12.2 square
miles in the townships of Eden and Empire in Fond du Lac County,

Its 68 megawatts are enough to power approximately 17,000 homes. After
construction was completed this fall, tests were conducted by Alliant
Energy and American Transmission Company (ATC) prior to beginning
commercial operation.

Our investment in Cedar Ridge helps us balance the need to provide
affordable energy to our customers while at the same time making sure
we are utilizing new technologies to reduce our impact on the
environment, said Barbara Swan, President WPL. We are extremely
grateful to the community leaders and residents of the Towns of Eden
and Empire for their tremendous support throughout this process.

In the next 20 years, Cedar Ridge Wind Farm is expected to offset as
much as 4.5 million tons of carbon dioxide, 3,500 tons of nitrogen
oxides, 6,000 tons of sulfur dioxides and 50 pounds of mercury. The
carbon dioxide avoided is roughly the equivalent of taking 155,000
standard-size automobiles off the road each year.

WPL’s commitment to the environment extends beyond the wind energy
being generated at Cedar Ridge. The Administration Building is
Leadership in Energy and Environmental Design (LEED) gold certified.
LEED is a performance-oriented rating system where building projects
earn points for satisfying criteria designed to address specific
environmental impacts inherent to the design, construction and
operation of the building.
Cedar Ridge is the latest example of Alliant Energy’s commitment to
renewable energy choices.

Building on an already-robust renewable portfolio, the company plans
to add an additional 400 megawatts of wind power to its portfolio by
the end of 2010. When those 400 megawatts are in commercial operation,
wind energy will make up nearly 850 megawatts, or eight percent, of
Alliant Energy’s overall energy mix.