RALEIGH -- About 2 million Duke Energy customers in central and western North Carolina would face an average 6% rate increase if state regulators approve the country's largest electric company's request. Duke Energy said Monday it needed another $290 million a year to recoup spending on grid upgrades, coal-ash cleanup, storm repairs and to increase its potential profit margin to 10.3%. The company also proposes recouping money faster for three coal-burning power plants, potentially leading to earlier closings.The proposal would add about $8.06 per month to the typical residential customer's bill.A rate increase that took effect last year was expected to increase residential rates by 1.2% over four years.The Duke Energy subsidiary serving eastern North Carolina is expected to file a new rate request within a month.In 2018, several major storms and hurricanes that impacted the state had Duke Energy contemplating a rate increase . In November 2018, Duke Energy Progress asked state regulators for permission to notify customers of a price increase to account for the costs of fuel and purchasing renewable energy.