Under some scenarios, a new Trump administration proposal to reduce carbon emissions from power plants could curtail the construction of new natural gas combined-cycle power plants by as much as 30% and increase the use of existing coal plants by 13%, according to the Environmental Protection Agency’s own regulatory impact analysis on its proposal, the Affordable Clean Energy (ACE) rule.

But the eventual outcome of the proposal, announced Aug. 21, will depend on a host of variables, including fuel cost and demand for renewable energy, says Andy Byers, director of environmental services for Black & Veatch.

“I kind of take it with a grain of salt,” Byers says of the analyses of the plan by EPA and others. “There’s a lot that could happen between now and 2025,” which is about the earliest the proposal could go into effect, he adds.

ACE was proposed as a replacement for the Obama Clean Power Plan, which dozens of states and groups opposed because they said it exceeded EPA authority. The U.S. Supreme Court stayed the rule in 2016. Compared with the Obama rule, which aimed to cut carbon emissions 32% below 2005 levels by 2030, EPA says ACE could pare 2030 CO2 emissions by just 0.7% to 1.5%.

Democrats say they will take legislative action against the rule, which by EPA’s own analysis could cause an additional 1,400 deaths because of particulate matter. About 200,000 people in the U.S. die each year because of particulate matter, according to scientific studies. Environmental groups also say the rule will increase carbon emissions.

In the meantime, the nation’s coal-burning utilities, including the Tennessee Valley Authority, say they will move forward with plans to shut their coal plants. TVA said on Aug. 22 it will study closing two of its six remaining coal-fired power plants for economic reasons.

Byers says most utilities with coal plants will probably analyze the rule and start examining their set of candidate technologies, including intelligent soot blowers, blower feed pumps and air heater and duct leakage control, to see how much they can help improve efficiencies of coal plants and whether those investments  would make economic sense.

As part of ACE, the EPA is proposing changes to its New Source Review permitting to allow coal plant owners to make efficiency upgrades without triggering a review. The proposal is open for public comments.