The EPA is still on the fence about whether withdrawing toxic air pollution standards for power plants would benefit the energy industry.

The Environmental Protection Agency doesn’t want to uphold a “costly,” “stringent” rule, but also can’t ignore what industry has already spent on compliance, Bill Wehrum, assistant administrator for air pollution, said.

“The bell has been rung, and if you make the regulation go away, you can’t make the costs that it incurred go away,”...