Mississippi Power Co. has asked state regulators to approve a 4.2 percent increase in its rates to offset higher fuel costs.

Mississippi Power, a Southern Company subsidiary, serves 183,000 customers in 23 southeast counties.

If the Public Service Commission approves the request, residential customers will see an increase of approximately 3 percent a month, company official said Thursday. Commercial and industrial customers will see higher increases because fuel costs make up a larger portion of their bills, the company said.

The typical residential customer uses 1,000 kilowatts of electricity a month.

“That customer is going to see an increase of $3.49 per month per 1,000 kilowatt hours,” said Mississippi Power spokeswoman Cindy Duvall. “Last year there was a 3.25 percent increase for residential customers.”

Any change to the bills will be effective for a year beginning in January.

Duvall said from 2007 to 2008, “our average for rail transportation is projected to increase 6 to 8 percent.”

Fuel costs account for more than half of Mississippi Power’s total operating costs.

“Fuel costs are recovered from customers on a dollar-for-dollar basis,” Duvall said. “No profit for the company is associated with fuel consumed.”

The PSC adjusts Mississippi Power’s rates up or down every year to reflect changes in the cost of fuel used to make electricity.