Aquila Inc. said Friday it was selling two peaking power plants in Illinois to St. Louis-based utility AmerenUE for $175 million.

The plants include the Goose Creek Energy Facility, a 510-megawatt plant in Platt County, and the Raccoon Creek Energy Facility, a 340-megawatt plant in Clay County. Both plants run only during peak periods for electricity consumption.

Both deals are expected to be completed in the first half of next year.

Aquila said it expected to record a pretax impairment charge of $160 million on the sale.

The Kansas City,Mo.-based utility built the two plants in 2002 as part of its expansion into the unregulated energy marketing business. Since then, Aquila has retreated from that sector to focus on just providing natural gas and electricity to its regular customers in seven states.