— North Carolina Attorney General Josh Stein has appealed Duke Energy’s most recent rate increase to the state Supreme Court.

The state Utilities Commission had approved an increase of about $5.22 a month for residential customers in the eastern half of North Carolina, including much of Wake County. Some of that money would go toward coal ash pond cleanups at Duke plants, which is one of the reasons Stein’s office asked the Supreme Court to take another look at the decision.

The Sierra Club has also filed an appeal in the case.

The attorney general argues that Duke’s violation of environmental regulations and criminal laws in dealing with coal ash and evidence that the company knew the risks of storing ash in unlined ponds well before the 2014 Dan River spill should have kept the commission from approving the increase.

In a statement Wednesday, Duke said it believes the increase decision was fair and noted that rates remain below the national average.

This case affects Duke Energy Progress customers. Duke Energy Carolinas, which powers much of the western half of the state, has its own rate increase before the Utilities Commission. Final briefs are due Friday in that case, and the commission will decide the increase later.