How much does Duke Energy want to raise your bill? We’ll know soon.

Duke Energy disclosed plans Tuesday to file a rate hike request next month, in a move that starts its efforts to pass expensive coal ash cleanup costs to customers in the Charlotte area.

The Charlotte-based electric utility, in a notice to the North Carolina Utilities Commission, said it expects to file the request on or around Aug. 25. Tuesday’s notice does not detail how much rates might increase, so the fallout for customer bills remains unclear.

Duke is expected to seek a base-rate increase for a service area that includes Charlotte and western portions of North Carolina. The move follows a similar request Duke Energy Progress submitted last month proposing a 16.7 percent jump for residential customers in a territory that includes eastern North Carolina and the Asheville area. That was the largest rate hike the Raleigh-based subsidiary has sought since it was called Carolina Power & Light in the 1980s.

August’s request will mark the first increase to base rates affecting residential and other types of customers across the Charlotte area since 2013. That year, Duke was given approval for a 5.1 percent average hike, which took typical bills up an additional $7.60 a month.

The latest hike comes after a 2014 spill of ash into the Dan River triggered legislation ordering Duke to close all 32 of its North Carolina ash basins. Duke has said its shareholders will be on the hook for fines and cleanup costs associated with the Dan River incident. The company has estimated its ash cleanup costs in the Carolinas to total $2.5 billion by 2021.

In addition to coal ash, Duke noted that Tuesday’s hike will also cover investments to modernize North Carolina’s electric system and generate cleaner power.

“It’s our mission to deliver an energy future that is safer, more reliable, and increasingly clean, powered by technology that gives customers access to more information, services and bill-lowering tools,” David Fountain, Duke’s North Carolina president, said in a statement.

Figures Duke released in February place coal ash cleanup costs in the Carolinas at nearly $5.2 billion over several years. Company documents Duke released at the time said “multiple” North Carolina rate hikes are likely by 2021.

Those would cover the costs of a $1.1 billion power plant Duke is building in Asheville and $10 billion in grid upgrades planned over the next five years, the company had said.

Tuesday’s notice begins what is expected to be a months-long process involving public hearings in Charlotte and elsewhere across the state before the commission makes a final ruling.

This story was originally published July 25, 2017 at 3:05 PM with the headline "How much does Duke Energy want to raise your bill? We’ll know soon.."