One of the largest U.S. utilities is weighing the retirement or repowering to lower-emitting fuel sources of several thousand megawatts of coal- and gas-fired power plants through 2028 while on the way to a goal of net-zero greenhouse gas emissions by 2050.

Southern Co. subsidiaries Georgia Power Co. and Alabama Power Co. recently filed plans with their respective state environmental authorities detailing how each utility expects to comply with the U.S. Environmental Protection Agency's effluent limitation guidelines, which apply to waste streams from coal-fired power plants. The guidelines, approved in 2020, exempt coal-fired plants that plan to close no later than the end of 2028 from compliance with new standards, which has prompted a number of planned retirements.

"With these expected changes ... Southern Co. will have announced total decreases in its coal generating capacity from more than 20,000 MW across nearly 70 generating units to less than 4,500 MW of coal capacity remaining at eight generating units," Southern Co. Chairman, President and CEO Thomas Fanning said Nov. 4, outlining some of the company's planned changes during its third-quarter earnings call. "This equates to a reduction of nearly 80%."

Among the changes, according to details shared in the third-quarter call and in a 10-Q filing, are the retirement by 2028 of coal-fired units, including the 757-MW unit 5 at the Barry plant in Alabama, units 1 and 2 at the Bowen plant in Georgia, the 860-MW unit 3 at the Scherer plant in Georgia, and both units at the 1,744-MW Wansley plant in Georgia. Also planned is the retirement of four gas-fired units at the E.C. Gaston plant in Alabama, all of which are roughly 60 years old.

The company also plans to potentially repower or retrofit existing coal plants to burn natural gas during peak loads. So far, Southern Co. announced potential plans to repower Gaston plant unit 5, now 832 MW, and the 362-MW Barry unit 4. All of the plans remain subject to state regulatory approval.

Southern Co. also identified several units for compliance with the revised effluent limitation guidelines, including units 3 and 4 at the Bowen plant and units 1 and 2 at the Scherer plant.

The four-unit Scherer plant is the largest operating coal-fired plant in the U.S., and ownership is split among seven utilities. Unit 4 is already slated for retirement in 2022; it is owned by NextEra Energy Inc. subsidiary Florida Power & Light Co. and the city of Jacksonville, Fla., utility JEA.

Other owners of the Scherer plant, with interests in units 1 and 2, include Oglethorpe Power Corp., the Municipal Electric Authority of Georgia and the city of Dalton, Ga.

Southern Co. previously announced plans to retire the two-unit 1,004-MW Victor J. Daniel Jr. coal plant in Mississippi, where ownership is shared by its subsidiary Mississippi Power Co. and NextEra subsidiary Gulf Power Co.

Retiring coal plants will free up operation and maintenance costs, Fanning said, adding, "We intend to use that O&M to basically allow for cost recovery, account for the incremental revenue requirements associated with new generation that will replace that and keep rates as low as possible for our customers."

The assets Alabama Power plans to retire or repower have net book values totaling about $1.5 billion, and Georgia Power's identified assets have a total net book value of about $2.2 billion, excluding capitalized asset retirement costs, Southern Co. said in its 10-Q filing.