EPA's proposed standard reflects a trend in the U.S. power sector to build cleaner plants, primarily new, clean-burning, efficient natural gas generation. The new standard is flexible is designed to help minimize carbon pollution through the deployment of the same types of modern technologies and steps that power companies are already taking to build the next generation of power plants, EPA said.

"If old King Coal isn't dead already, he's certainly teetering toward life support," Frank O'Donnell, president Clean Air Watch said in Washington today, commenting on the EPA's proposed emission rules for new power plants.

At present, there is no uniform national limit on the amount of carbon pollution that new power plants can emit. Operators of fossil power plants in the U.S. currently primarily weigh up the cost of coal versus natural gas when considering how to fuel their plants. Now, the new EPA standards proposals are expected to turn the tide towards gas-to-power generations as gas-fired plants emit significantly less carbon emissions than coal-fired plants.

"We're putting in place a standard that relies on the use of clean, American made technology [for new and planned power plants] to tackle a challenge that we can't leave to our kids and grandkids," EPA Administrator Lisa P. Jackson said when unveiling the new rules on Friday last week.

As a direct result of the Supreme Court's 2007 ruling, EPA in 2009 determined that greenhouse gas pollution threatens Americans' health and welfare by leading to long lasting changes in our climate that can have a range of negative effects on human health and the environment.