Correction: An earlier version of this article misstated the unit of measure for greenhouse gas emissions. It is pounds per megawatt hour, not per megawatt. This version has been corrected.

The proposed EPA rule — years in the making and approved by the White House after months of review — will require any new power plant to emit no more than 1,000 pounds of carbon dioxide per megawatt of electricity produced. (Daniel Acker/BLOOMBERG)

The Environmental Protection Agency will issue the first limits on greenhouse gas emissions from new power plants as early as Tuesday, according to several people briefed on the proposal. The move could end the construction of conventional coal-fired facilities in the United States.

The proposed rule — years in the making and approved by the White House after months of review — will require any new power plant to emit no more than 1,000 pounds of carbon dioxide per megawatt hour of electricity produced. The average U.S. natural gas plant, which emits 800 to 850 pounds of CO 2 per megawatt hour, meets that standard; coal plants emit an average of 1,768 pounds of carbon dioxide per megawatt hour.

Costly controls

Industry officials and environmentalists said in interviews that the rule, which comes on the heels of tough new requirements that the Obama administration imposed on mercury emissions and cross-state pollution from utilities within the past year, dooms any proposal to build a coal-fired plant that does not have costly carbon controls.

“This standard effectively bans new coal plants,” said Joseph Stanko, who heads government relations at the law firm Hunton and Williams and represents several utility companies. “So I don’t see how that is an ‘all of the above’ energy policy.”

The rule provides an exception for coal plants that are already permitted and beginning construction within a year. There are about 20 coal plants now pursuing permits; two of them are federally subsidized and would meet the new standard with advanced pollution controls.

An administration official who asked not to be identified because the rule hasn’t been announced wrote in an e-mail Monday night: “This standard provides a clear and certain path forward for industry and the important domestic energy sources they rely on” for electricity generation.

The proposal does not cover existing plants, although utility companies have announced that they plan to shut down more than 300 boilers, representing more than 42 gigawatts of electricity generation — nearly 13 percent of the nation’s coal-fired electricity — rather than upgrade them with pollution-control technology.

Michael Brune, executive director of the Sierra Club, said the new rule “captures the end of an era” during which coal provided most of the nation’s electricity. It currently generates about 40 percent of U.S. electricity.

The power sector accounts for 40 percent of the nation’s greenhouse gas emissions, and Brune said it is “the only place where we’re making significant progress” in curbing greenhouse gas emissions linked to climate change, adding that “at the same time, it’s not sufficient.”

Cheap natural gas is also contributing to the closure of aging coal-fired plants, as many utilities switch over to gas plants, which produce about half the carbon emissions.

“Gas is contributing to the closure of these plants,” Dominion Resources chief executive Thomas F. Farrell II said in an interview last week. Farrell, who also chairs the Edison Electric Institute, the utility trade association, added: “It’s not all EPA. It’s a combination of low gas prices and EPA working at the same time.”

National Mining Association spokesman Luke Popovich said the proposal shows that President Obama is following through on his pledge to reduce greenhouse gas emissions through means other than legislation.

Bypassing Congress

“After Congress refused to pass carbon caps, the administration insisted there were other ways to skin the cat, and this is another way — by setting a standard deliberately calculated to drive affordable coal out of the electricity market,” Popovich said.

Conrad Schneider, advocacy director for the Clean Air Task Force, said the proposed rule will ensure a cut in the nation’s carbon output even if gas prices spike.

The proposal will provide some flexibility, allowing super-efficient coal plants an exemption for the first decade of operation before requiring them to reduce their carbon emissions by more than 50 percent.

The EPA rule, called the New Source Performance Standard, will be subject to public comment for at least a month before being finalized, but its backers said they were confident that the White House will usher it into law before Obama’s term ends.

“The Obama administration is committed to moving forward with this,” said Nathan Willcox, federal global warming program director for the advocacy group Environment America. “They’re committed to doing it this, and we’re committed to helping them do it.”

Staff writer Steven Mufson contributed to this report.