The Iowa Utilities Board turned away arguments that the proposed expansion would give MidAmerican an unfair competitive advantage over smaller rivals.

MidAmerican claims to be the US leader in ownership of wind-powered electric generation among rate-regulated utilities. It has more than 1,390MW in operation, under construction and under contract in Iowa.

Location of the proposed wind farms has not been decided, according to the utility, which serves about 634,000 retail customers in Iowa.

Utility officials did not estimate cost of adding new wind power but told regulators that electric rates will not increase as a result. The company is based in the state capital of Des Moines.

Iowa is the second wind energy producer behind Texas with more than 3.050MW..