The N.C. Utilities Commission approved an overall 7 percent rate increase Friday for Duke Energy's 1.8 million customers in the state, starting next month.

Monthly bills for typical residential customers will go up about $7.

The commission largely adopted an earlier settlement among Duke, the commission's Public Staff, which represents consumers, and Time Warner Cable, a major customer for Duke.

N.C. Attorney General Roy Cooper, who opposed the settlement, immediately challenged the order. "We intend to review the opinion and look at available options," Cooper said.

Duke initially had sought a 15 percent hike, its second since 2009, to pay for the $4.8 billion it has spent on power plants and pollution controls since then. Customers reacted angrily, filing hundreds of letters of protest.

Duke's N.C. president, Brett Carter, said the settlement "balances the company's need to recover investments made in the electric system with the reality that many of our customers face continued economic challenges."

But the utility said it will seek a third rate increase later this year as two new power plants begin generating electricity.

The increase approved Friday will bring Duke $309 million a year in additional revenue. It allows Duke a 10.5 percent return on common equity, or profit margin.

Duke agreed to donate $11 million of shareholder money to community nonprofit groups to help low-income residents with energy costs.

The commission order made a few changes to the Duke-Public Staff settlement agreement.

One addressed complaints about inequities between industrial and commercial customers using similar rate schedules.

While Duke's cost of service to both classes is about the same, commercial customers said they paid more than industries, amounting to a $25 million subsidy for industrial customers.

The commission ordered Duke to reduce the rate differential by one-third.

The commission in 2009 allowed Duke to raise its N.C. rates by 7 percent spread over two years.