Brattle Group economists have projected 59,000-77,000 megawatts will be lost through retirements, costing the industry $US126-$144 billion in retrofits and capacity replacements.

The range is about 25,000MW more than it estimated in a 2010 report.

The numbers also exceed other reports released in recent months, including the Electric Power Research Institute’s forecast of 36,000 to 61,000MW lost over the next several years.

“Everything else being equal, this amount of retirement will be enough to increase prices in both electric and gas markets for a few years. But we do not envision that impact to be large or persistent enough to alter retirement decisions," principal and study co-author Frank Graves said.

The company said that since it last released estimates in December 2010, power demand had dropped while natural gas prices have taken the same downward turn, the latter creating a run on gas-fired electricity.

With the change in conditions, retirement announcements accelerated and by July 2012, shutdowns of about 30,000MW of coal plants, or 10% of the nation’s coal capacity, were expected by 2016.

Because some of the regulations introduced by the US Environmental Protection Agency still need to be finalized, Brattle said the uncertainty left it to develop strict and lenient scenarios.

It estimates that 59,000MW will likely retire under lenient rules, and 77,000MW would cease to exist under strict regulations.

“Final regulatory requirements are still unresolved, but the authors suspect they will be akin to the lenient scenario,” the economists said, adding that projections are also sensitive to market conditions in the future, including natural gas prices going forward.

In all, the firm’s analysis indicated that future coal retirements would be more than double the level announced to date.

“The impacts will be modest over large areas, but more acute locally, especially for owners of smaller fleets that are predominantly coal-based,” Graves said.

“Everything else being equal, this amount of retirement will be enough to increase prices in both electric and gas markets for a few years, but we do not envision that impact to be large or persistent enough to alter retirement decisions.”

The study “Potential Coal Plant Retirements: 2012 Update,” was co-authored by Graves and fellow Brattle principal Metin Celebi along with research analyst Charles Russell.