America’s oldest coal plants are retiring like they’re Baby Boomers, and some of them are the same age. About 17 percent of U.S. coal-fired power generation will vanish in the next few years — some 7.5 percent this year alone, according to Bloomberg New Energy Finance. Obstacles facing coal plants include their age, the abundance of cheap natural gas and a new EPA rule that begins taking effect April 16.

The new Mercury and Air Toxics Standards requires that coal plant owners limit poisons such as mercury, arsenic, and metals, which have previously freely spilled into the atmosphere and waterways.

The Supreme Court will weigh in on the rules at the end of this term. But with plants this old and gas this cheap, most of these plants are set for closure or conversion to gas, regardless. A chunk of these old plants, in red, are standing by while their fates are determined.

America’s approximately 300 gigawatts of coal-burning power capacity makes up 30 percent of the national total.