America’s older coal generators are dirtier, less efficient and less utilized than the rest of the country’s coal fleet. And a report from the Union of Concerned Scientists has found they’re not economically viable either.

The report’s authors looked at each coal generator in the U.S. and determined whether its operating costs would be higher than those of a natural gas generator when updated with any of the pollution controls for sulfur dioxide, nitrogen dioxide, mercury or soot that it lacked. It found that up to 353 coal-fired generators in 31 states are “ripe for retirement” – meaning adding upgrades important to the health of communities and the planet was more costly than retiring the coal plant or using natural gas and renewable energy.

The 353 generators, which account for about six percent of the nation’s power supply, are in addition to the UCS’s estimated 288 units that have already been scheduled for retirement in the U.S. According to the report, the two groups of generators – those which are ripe-for-retirement and those which will be closing soon – have a lot in common:
•On average, the ripe-for-retirement generators are 45 years old – 15 years past the 30-year average lifespan of a coal generator and 5 years shy of the average age of the 288 generators slated for closure.
•The two groups of coal generators are dirty – more than 70 percent of the generators identified as ripe-for-retirement lacked at least three out of the four pollution control upgrades accounted for in the study. The same is true for 88 percent of the soon-to-be-closed generators.
•The two groups are under-utilized. On average, ripe-for-retirement generators operate at 47 percent of their power generation capacity, while the generators slated for closure operate at 44 percent. The total U.S. coal fleet operates at 64 percent of its capacity.

The report found the ripe-for-retirement generators were primarily located in the Southeast, with Georgia, Alabama, Tennessee and Florida containing the most, followed by Michigan. Southern Company, which operates in Georgia, Alabama and the Florida panhandle, owns about 27 percent of the 353 ripe-for-retirement units, but has announced the fewest number of closures when compared to other large energy companies, including Tennessee Valley Authority and Duke Energy Corp.

These findings make clear that, as America’s existing coal fleet ages and natural gas and renewable energy sources become more affordable, it will be the energy market – not environmental regulations – that plays the largest role in phasing out coal in the country. Even without accounting for needed pollution controls updates, the report found that about 40 percent of the ripe-for-retirement coal generators are more expensive to operate than existing natural gas plants.

“Consumers are hearing, especially during the election, about the EPA’s war on coal and how we need to keep coal plants open, and our analysis provides good information to show that that’s not necessarily the case,” Steve Clemmer, research director of the UCS’s climate and energy program and one of the report’s authors, said during a webcast Wednesday.

Replacing the 353 ripe-for-retirement and 288 scheduled-to-close generators with natural gas generators would reduce U.S. carbon dioxide emissions by approximately 245 million tons per year — equivalent to 9.8 percent of U.S. power sector CO2 emissions in 2010. Of course, natural gas is not a long-term solution to climate change, and the report notes that if ripe-for-retirement generators are closed, state governments should incorporate renewable energy and energy-saving technologies into its replacement energy sources.