Great River Energy will close its Stanton, N.D., power station in May 2017, saying the coal-fired plant is no longer economical to operate.

The relatively small plant dates to 1966 and employs 65 workers.

The Stanton station's shutdown is part of a wave of planned coal-fired power plant closings in the U.S., as utilities shift to cheaper natural gas-fueled generators and look to shed power sources that emit more greenhouse gasses.

Maple Grove-based Great River is a cooperative that supplies wholesale power to 28 Minnesota electricity cooperatives, which in turn serve 665,000 customers. Great River's biggest plant is a coal-fired operation in Underwood, N.D., with a generation capacity of 1,146 megawatts. The Stanton plant, in contrast, has a 189-megawatt capacity. A megawatt is a million watts.

The Stanton station, located in west-central North Dakota, has been generating power on a "limited basis," Great River said in a prepared statement. It's often been more affordable for Great River to run its other plants more — or purchase power in the regional market — than to operate Stanton.

Great River has several natural gas-fired plants in Minnesota; the largest is a 513-megawatt operation in Lakefield in the state's southwest corner. The company also purchases power from at least five Upper Midwest wind farms.