The company previously said it would retire the Buck and Riverbend steam stations in two years in advance of forthcoming federal environmental regulations.

Buck units 5 and 6 and Riverbend units 4 through 7 will instead be closed on April 1, bringing more than 80 years of operations at each facility to a final stop.

They are the oldest facilities in the state.

Officials said the units had been operating infrequently in recent years and with new and more efficient plants and natural gas prices, future operations would be cut even more.

Also playing a role in the decision was the success of the now-merged company's joint dispatch process, which utilizes generation across both Duke Energy Carolinas and Progress Energy Carolinas fleets.

It said the process was more efficient in meeting customer needs and the dispatch procedure would help it meet its $US687 million merger-related savings commitment.

“The investments we and our customers have made in the last 10 years allow us to retire older stations like these and continue transitioning to cleaner sources of electricity," Duke regulated utilities executive vice president and chief operating officer Keith Trent said.

“These stations played pivotal roles in the 1920s and 1930s in helping to electrify the industries and homes of the Carolinas and we honor all those employees who contributed their time and talents over the years to ensure safe, reliable operations.”

Buck steam station in Rowan County first went into commercial operation in 1926.

It was Duke's first large-scale power plant.

Its original two units retired in 1979 and units 3 and 4 retired in May 2011.

Units 5 and 6, at 128 megawatts each, went online in 1953 and three smaller natural gas combustion turbines at the site retired last October.

The 620MW natural gas Buck combined cycle station began operations in November 2011.

Riverbend steam station in Gaston County began operating in 1929.

Units 1 and 2 of the complex retired in 1979 and unit 3 retired in 1976.

Units 4 and 5, at 94MW each, began operating in 1952, while the 133MW units 6 and 7 began operating in 1954.

Four smaller natural gas combustion turbines there also retired last October.

Duke said it would “make every effort” to assist the 65 impacted employees in finding opportunities within the company or would provide severance to eligible individuals.

By the end of this year, officials said, Duke would have retired more than 3800MW of capacity.