The public staff for the state Utilities Commission and Duke Energy have reached an agreement on Duke's request for a 13 percent residential rate increase to cover operating expenses.

The propsal, which must be approved by the Utilities Commission, would allow Duke to raise residential rates by about 7 percent over two years, said Robert Gruber, executive director of the Utility Commission's public staff.

The two-year increase will add $7.31 to the monthly bill for a household that uses 1,000 kilowatt hours of electricity. Currently, a Duke Energy customer using 1,000 kilowatt hours a month pays $90.19.

The first of the two rate increases will occur Jan. 1 and will add $3.70, or 4 percent, to an average residential customer's bill.

Duke's request for a 13 percent increase would have added about $11 a month to residential bills. Duke raised rates by about 5 percent on Sept. 1 to offset higher energy prices.

The Charlotte-based utility has 4 million electricity customers in five states, including about 160,000 in the western Triangle.