The Associated Press set out to determine which power plants in the U.S. would retire or be at risk of retirement because of two new air pollution regulations.
One data source was the Environmental Protection Agency, which had used computer models to predict which fossil-fuel-fired generating units are likely to retire early to comply with each of the rules, separating them from those that are likely to retire anyway.
The AP then contacted every company with a plant predicted to retire early based on EPA modeling to determine whether the prediction was accurate, and whether plants were missing from the EPA's list. The AP also called companies that appeared on other lists, but were not flagged by the EPA, to determine their status.
Based on interviews with each of the companies, the AP characterized the plants as "retiring" or "at risk". Plants converted to natural gas or another fuel, or scheduled for pollution controls, were removed from the list. If the company attributed the retirement mainly to economics, state laws or other reasons, the AP also removed the plants. Companies unsure how they were going to comply, but which said retirement was not a serious consideration, were also not counted.
The analysis found generating units at more than 32 plants in 12 states retiring due in part to EPA regulations. The AP identified units at another 36 plants in 16 states at risk of retirement.
The AP included the 4,000 megawatts of capacity estimated to retire by Southern Co., a major producer of power from coal, in its calculations of how much power production would be lost. However, the company would not identify the specific units it planned to retire, so the AP's total number of plant retirements could not be precise.