Montana-Dakota Utilities Co.'s electric customers will be paying slightly higher bills because the company's surplus power sales goals fell almost $1 million short last year, state regulators say.

Starting this month, MDU electric customers will see a charge of less than three thousandths of one cent per kilowatt hour on their electric bills, the Public Service Commission said Wednesday.

Susan Wefald, the commission's president, said the charge equals an extra $1.65 on the bill of a residential customer who uses 750 kwh per month. It will last until March 31, 2008.

Since April 2005, MDU customers have been sharing the utility's market risk for surplus power sales as part of the settlement of an MDU request to increase its electric rates.

The utility must reach a $6.5 million profit benchmark from surplus power sales before MDU begins granting electric-bill credits to its customers.

Until now, the plan has resulted in $2.73 million worth of credits on the bills of MDU's electric customers, commissioners said. The present credit equals $1.13 on the monthly bill of a residential customer who uses 750 kwh.

However, the Bismarck-based utility fell $1.08 million short of the profit benchmark last year, and Wefald said customers must make up the difference.

"At this point, we're still ahead of the game by setting this up," she said. "However, we are going to be watching it carefully this year."

One reason for the shortfall is that Montana-Dakota had less power to sell. Basin Electric Power Cooperative has been supplying MDU with 66.6 megawatts of electricity from its Antelope Valley plant in western North Dakota. However, the supply contract ended last October and was not renewed, Commissioner Tony Clark said.