Alliant Energy said it is looking to expand its 200MW Whispering Willow project in Franklin County, northern Iowa.
It said it was looking to maximise the renewable energy tax credit, following the five-year extension of the production tax credit in December.
Developers must begin construction or have spent a proportion of project capital by the end of 2016 to qualify for the full PTC before it begins its phase out.
"Our customers expect low-cost, clean energy, which is exactly what this project will bring to the communities we serve. Wind has no fuel costs and zero emissions, making it a win-win for Iowans and the Iowa economy," said Doug Kopp, president of Alliant Energy's Iowa utility.
Alliant Energy said it also generates an additional 1GW and purchases 600 megawatts of wind power in Iowa, Minnesota and Wisconsin.
Vestas will service the Whispering Willow project for another five years through its UpWind Solutions subsidiary. The project currently comprises 122 Vestas V82 1.65MW turbines, according to Windpower Intelligence, the research and data division of Windpower Monthly.
The announcement from Alliant comes after Warren Buffet's MidAmerican Energy announcing a $3.6 billion investment in building 2GW of wind in Iowa in April.
Vestas signed a conditional agreement in June to supply turbines to the 2GW MidAmerican cluster.
Iowa has over 6.3GW of installed capacity, according to the American Wind Energy Association's latest quarterly report.