Duke Energy says its customers will benefit from a new deal on costs for closing the company’s coal ash basins in North Carolina.

The agreement announced Monday is between Duke Energy, North Carolina officials and the Sierra Club, a conservation group.

Duke Energy Spokesperson Meredith Archie says this is a “milestone agreement” for the state.

Archie says the plan puts the coal ash debate to rest in North Carolina and assists as the company transitions to cleaner energy sources.

This latest plan would reduce the costs to Duke Energy’s North Carolina customers by $1.1 billion over a 15-year period from 2015 to 2030.

The agreement still needs the approval of state regulators.

Archie says the agreement does not change the operations at the H.F. Lee Plant in Goldsboro, where Duke Energy has begun recycling the over 6 million tons of coal ash at the site.