RALEIGH, NC (AP) - One of Duke Energy's North Carolina divisions wants to raise electricity rates by an average of 15 percent to pay for system upgrades, conversion to more natural gas and cleaning up coal ash pits.

The nation's largest electric company filed the request Thursday with state utilities regulators for customers of Duke Energy Progress, which operates in much of eastern North Carolina and Asheville. A separate request affecting Duke Energy Carolinas customers in Durham and western North Carolina could come before the state Utilities Commission later this year.

READ: Clever Ways to Lower Your Electric Bill

Duke Energy Progress last sought a rate increase in 2012, when it wanted an average 14 percent increase for households and 9 percent for commercial and industrial customers. The utilities commission approved and the state Supreme Court allowed an average 5 percent increase.

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