Part of the new Affordable Clean Energy rule announced Tuesday would focus on making coal plants more efficient — which could help them run for longer. But utility advocates say that’s unlikely to change energy companies’ plans.

Environmentalists are concerned that if the country’s coal plants become more efficient, then utilities will use the energy from coal more often — sending more harmful pollutants into the air.

But Indiana Energy Association President Mark Maassel says although it’s too early to tell, utilities are unlikely to shift gears toward more coal in their energy mixes.

“At the moment the single biggest driver in power plant decision making is the price of natural gas, the cost of that fuel,” he says.

Maassel says that price is projected to remain low and renewable energy sources are also becoming more affordable.

READ MORE: How The Rule Replacing The Clean Power Plan Might Affect Indiana

Maassel also says a power plant is a roughly 30-year investment that utilities don’t take lightly. He says plans to open or close a plant are usually made years in advance through the utility’s Integrated Resource Plan.

“So to suddenly change one way or the other is actually somewhat unlikely,” says Maassel.

We reached out to Duke Energy and Vectren for comment, but the utilities say they are still in the process of reviewing the rule.

The Affordable Clean Energy rule is the Trump administration’s replacement for the Obama-era Clean Power Plan.

Indiana Environmental reporting is supported by the Environmental Resilience Institute, an Indiana University Grand Challenge project developing Indiana-specific projections and informed responses to problems of environmental change.