The Obama administration is defending its plans to crack down on industrial pollution after a report from a utility group found proposed regulations may result in tighter U.S. power supplies.

The North American Electric Reliability Corp released a study on Tuesday that found four possible Environmental Protection Agency rules could “accelerate the retirement of a significant number of fossil fuel-fired power plants”.

Utilities may have to replace or make efficiency gains for up to 70 gigawatts, or about 7 percent, of U.S. power generation by 2015, the study said.

The EPA disputed those findings on Wednesday, saying the report by the industry group relied on faulty assumptions.

“By NERC’s own admission, its projections about electricity supply impacts rest on its own fortune-telling about future regulations that have not even been proposed yet,” EPA spokesman Brendan Gilfillan said in a statement.