Dive Brief:

• Alliant Energy on Tuesday announced it would retire its 1,100 MW Columbia Energy Center, making the company's subsidiary Wisconsin Power & Light coal-free by 2025.

• The announcement leaves three coal plants remaining in Wisconsin without planned retirement dates. Alliant plans to produce net-zero electricity by mid-century, and still owns six coal fired plants in its Iowa portfolio, three of which do not yet have a planned retirement date.

• Duke Energy on Tuesday also announced it would be shuttering a coal plant unit — the utility notified North Carolina regulators it has plans to shutter its 270 MW Allen Unit 3 by March 31. The Allen plant is a 1,140 MW, five unit facility, and will be fully retired by 2024.

Dive Insight:

Alliant and Duke's announcements are the latest in a spate of utility decisions to end operations of their coal plants, largely due to economic factors. More and more companies are turning toward cheaper, cleaner generation such as wind and solar, particularly as they pursue lower carbon emissions.

"The closure of Columbia is truly a historic moment as we stop burning coal in our Wisconsin Operations and fully turn our attention to generating cleaner energy using renewable resources, such as solar, battery storage and high efficiency gas," said David de Leon, president of Alliant Energy's Wisconsin energy company in a statement. The utility co-owns the plant with Wisconsin Public Service Corporation, a subsidiary of WEC Energy Group, and Madison Gas and Electric Company. Unit 1 will retire by the end of 2023, and unit 2 by the end of 2024.

In May, the utility announced it would retire its other Wisconsin coal facility — the last 380 MW unit of the Edgewater plant — by the end of 2022. A study released by Sierra Club in 2019 found the unit lost $8.3 million in net energy market revenues in 2016, after its $26.2/MWh production costs remained above median power market prices every month of that year. Sierra Club had also hoped to see Alliant retire its Columbia plant before 2030.

"By acting now to move away from coal to clean energy, Alliant Energy is putting words into action at a critical time," said Elizabeth Katt Reinders, deputy director of Sierra Club's Beyond Coal Campaign, in a statement. Shutting the plant early will help save the company over $250 million in operating costs, according to de Leon, and will help the company cut emissions 50% by 2030. The company plans to eliminate all coal from its portfolio, including in Iowa, by 2040.

Alliant is aiming to add 1,000 MW of new solar in Wisconsin by 2023, and has announced plans for 675 MW thus far, intending to make further announcements "in the coming months," according to the utility.

Duke is moving up its Allen unit retirement date by nine months — originally the plant was scheduled to come offline by Dec. 31. It must retire three of its Allen units by 2024, following a 2016 settlement with environmentalists over the utility's violations of the Clean Air Act. Units 2 and 4 of the plant are listed for 2022 retirement, and 1 and 5 are slated for 2024.

Unit 3 was placed in service in 1959, making it 62 years old, according to Duke, which said in its filing that the unit "has reached the end of its useful life."

Based upon the unit's condition and economic evaluations, the Company has determined that Allen Unit 3 will "no longer provide economic and reliable commercial service to customers," the filing reads. 

"We applaud Duke's decision to retire Allen Unit 3, which has been running since Eisenhower was in the White House, and a decade before astronauts first walked on the moon," said Will Harlan, senior representative for the Beyond Coal campaign in the Carolinas, in a statement. "We hope this is a signal of a larger effort to retire the rest of their uneconomic, polluting coal fleet and replace it with the clean, safe, affordable renewable energy customers have been demanding for years."