CHEYENNE - Rocky Mountain Power customers in Wyoming will see a slight uptick in their electrical rates starting today.

The state Public Service Commission this week approved an increase of nearly 5 percent for residential customers, which for the average household will mean paying around $2.85 more a month.

The increase will boost revenue for Rocky Mountain Power by $23 million a year, a sum the company says it needs to cover the costs of higher wholesale power prices and investments in new generation, transmission and distribution facilities.

The increase comes on the heels of a larger April 1 increase that will generate $31 million and allow Rocky Mountain Power to recoup a number of unanticipated expenses, including the high cost of wholesale power purchased when prices were spiking last summer. That increase is temporary and could be reduced by ruling of the Public Service Commission.

"Rocky Mountain Power understands that electricity is a basic service and is doing everything possible, including reducing internal costs, to keep prices for Wyoming customers among the lowest in the nation," said Jeff Hymas, a spokesman for the Utah-based company.

Rocky Mountain Power is Wyoming's largest public utility and provides about 57 percent of the state's electricity. The utility serves nearly 130,000 customers, including many in the Casper area.