Interstate Power and Light (IPL), a subsidiary of Alliant Energy, will file this week a request with the Minnesota Public Utilities Commission (MPUC) to increase its Minnesota retail electric rates.

IPL’s request seeks to increase annual revenues by approximately $15m, or 22%. The company is requesting a return on common equity of 10.5% and a regulatory capital structure of 46.8% common equity, 41.9% long term debt, 6.4% short term debt and 4.9% preferred equity.

The MPUC has sixty days after IPL’s filing to issue a decision on the company’s request to implement interim rates. IPL anticipates implementing interim rates, if approved, in July 2010. The company has proposed an annual electric revenue interim rate increase of approximately $14m, or 21%.

Interim rates will remain in effect until the MPUC issues a final decision on the company’s electric rate request, expected in the second quarter of 2011. If the final electric revenues approved by the MPUC are lower than the interim revenue levels, IPL will issue refunds equal to the difference between the interim and final rate levels, plus interest, the company said.