The Environmental Protection Agency (EPA) is floating new CO2 emissions regulations, but meeting them might be tricky.

Clean-burning natural gas is most likely to get the tap on the shoulder. Coal use in existing power plants will have to be slashed.

In 2013, coal fires generated 39% of the nation’s electricity, while natural gas and nuclear generated 27% and 19%, respectively. Environmentalists emphasize the prospects of renewable sources, yet wind, solar and other forms accounted for just 6% of electricity generation.

Jack Gerard, president and CEO of the American Petroleum Institute, raised concerns about the EPA’s proposed regulations, announced June 2, on greenhouse-gas emissions from existing power plants.

The EPA's proposal targets CO2 pollution and sets a goal of reducing emissions from existing power plants by 30% from 2005 levels by 2030.

“This proposal is not consistent with the administration’s own ‘all of the above’ energy strategy,” Gerard said. “The uncertainty created will have a chilling effect on energy investment that could cost jobs, raise electricity prices and make energy less reliable. The energy sector is already one of the most heavily regulated industries in the United States.”

The EPA's proposed CO2 regulations assume a 25% cut in coal and a 35% increase in gas-fired generation by 2020, according to analysis by Bernstein Research.

Gerard pointed out that the air is getting cleaner under existing regulations, and that carbon emissions are down due to technological advancements developed by the private sector.

“We can continue to make environmental progress without damaging the economy,” he said.

Benchmarked to 2005 emissions levels, the EPA's 30% CO2 reduction target “is far less ambitious than it sounds,” said Hugh Wynne, a senior analyst at Bernstein Research, in a June 3 report.

In 2013, U.S. energy-related CO2 emissions were 10% below 2005 levels. Emissions in 2013 were roughly 2% above their 2012 level, according to the U.S. Energy Information Administration.

Between 2005 and 2011, all four Census regions—West, South, Midwest and Northeast—experienced emissions declines, with the Northeast experiencing larger emissions reductions than the other regions. Underlying state-level emissions changes created an even wider spread. Nebraska (Midwest) saw a 20% emissions increase, while Nevada's (West) emissions fell 33%.

Regional and subregional spreads reflect differences in local energy economics, population distribution and other factors. For instance, Nebraska's emissions profile was affected by the expansion of the biofuels industry, increased crude production and the temporary closure of a nuclear power plant.

Wynne said laws and regulations on the books today are expected to achieve a further 9% reduction in utility CO2 emissions by 2017, when the EPA's new CO2 regulations would begin to take effect.

By then, power sector emissions of CO2 will stand about 19% below 2005 levels, limiting the reduction to be achieved by the new regulations to 11% off of the 2005 base, Wynne said.

Bernstein Research calculated changes in power sources based on the EPA's proposed CO2 emissions target of 1,777 million metric tons for the U.S. in 2020.

How to cut 30% of CO2 emissions

National coal-fired generation

25% reduction by 2020.

Coal-fired generation

35% increase (achieved by increasing the existing fleet of combined-cycle gas turbines to 75% from 45%).

Nuclear power

12% increase, primarily reflecting capacity additions from new nuclear power.

Renewable generation

28% increase, assuming compliance with various states' renewable portfolio standards.

Source: Bernstein Research

Opposition to the plan has come from many corners.

The International Brotherhood of Electrical Workers (IBEW) said President Obama’s goals may be laudable, but wind and solar power are simply not ready to replace other fuel sources needed to meet electric power demand.

“The EPA has a track record of underestimating the impact of its rules, making faulty predictions that have cost tens of thousands of good jobs,” the group said in statement.

In 2011 the IBEW and several other unions testified before the agency, predicting that 56 gigawatts of generation would be lost due to plant closings under then-proposed rules. The EPA estimated only 4.7 gigawatts would be lost.

“Approximately 90% of the plants scheduled to close were required to run during last winter’s polar vortex to prevent grid disruption,” the IBEW said. “We will critically examine the new rules to determine how much additional capacity could be lost.”

Frances Beinecke, president of the Natural Resources Defense Council (NRDC), wrote in her blog that an April poll by the Yale Project on Climate Change Communication found the public supported carbon pollution limits by a 2-to-1 margin.

She touted wind power for cutting carbon pollution by 10% in 13 states, and efficiency standards for appliances for cutting consumer costs.

“And yet, big polluters and their allies in Congress are already attacking carbon limits and claiming America can’t generate energy without fouling our air and destabilizing our climate,” she said. “I know that’s not true.”

The new proposal may seem a negative headline for the coal industry and a positive for the renewable energy sector and related industries, but reality is a bit more complicated, said Pearce Hammond, managing director and co-head of exploration and production research for Simmons & Co. International.

“The Carbon Pollution Standards are simply a proposal, and it remains likely that at least some changes will occur before a final rule is scheduled to be issued in June 2015,” he said. “It also seems likely that the proposal will encounter vigorous legal, political, and industry opposition.”

The mandated 30% decline in CO2 emissions by 2030 is less than some worst-case fears. The NRDC has advocated for a proposal that would cut emissions by 21% to 31% by 2020, and 25% to 36% by 2025.

The aging coal fleet already made at least some decline in coal generation likely over the longer term, Hammond said.

“Longer-term, future export thermal opportunities could potentially offset declining domestic thermal coal demand,” he said.