Duke Energy, the state's largest electric utility, will raise customer rates in January under an approval this morning from the N.C. Utilities Commission.

The effect on a typical residential customer will be about $7 a month, but the actual amount will vary by house size and energy usage.

The Charlotte-based power company will phase in the rate increase over two years. The company will raise rates 3.8 percent in January and raise rates again by 3.2 percent in 2011.