McCarthy noted that her agency has consulted with a broad set of stakeholders ahead of writing the proposal that is now undergoing White House vetting ahead of a June release. But she said the conversation would not end when the proposal is made public. The final rule released in June 2015 will look substantially different from this spring’s proposal, she said, in part because of subsequent discussions with stakeholders and the states.

The proposed document — which was written during the autumn and winter months — will “tee up a number of ideas” for how states could structure their plans, McCarthy said.

“There is enormous flexibility in the definition of a state plan, and our ability to look at the timeline for achieving that — for submitting the plans and for achieving the reductions,” she said. “And we’re going to take full advantage of that in this proposal, so that we can have more concrete discussions as we move forward.”

President Obama’s memorandum signed last year asked states to submit their implementation plans to EPA by the end of June 2016 in order to allow the agency to accept or reject them before the end of his administration. Reductions are set to phase in by 2020.

McCarthy said again that the proposal would recognize the differences between utility sectors in different states and would avoid interfering with their resource management planning or compromising reliability.

But she said it would require states to make demonstrable emissions reductions.

“This carbon pollution standard is going to be federally enforceable,” she said. “It is going to be a requirement. It is not going to be an aspirational goal that ‘if everything else goes right, it ought to happen.'”

EPA will vet the plans to see if they make the reductions the guidance requires, she said.

McCarthy shared the stage with Colette Honorable, president and chairman of the board of the National Association of Regulatory Utility Commissioners.

Honorable, who also heads the Arkansas Public Service Commission, said utility regulators did not expect EPA to accept plans that would not result in carbon reductions. But she said many states are working to better integrate renewable energy and efficiency into their power systems, and those efforts should be counted toward any reduction goal the federal agency puts forward.

“We aren’t saying, ‘Let’s throw it all up against the wall and see what sticks,'” she said. “We are saying we have demonstrated, proven, cleaner energy options. And it would be a shame not to allow these efforts going on across the country to support the work Gina is speaking of.”

But Honorable noted that regulators from different states have drastically different positions about what EPA should and should not do in its rule. NARUC advocates only for positions that are a consensus among its members, she said. The organization adopted a resolution late last year urging EPA to ensure that its guidelines credit states for the emissions reductions they have already made and not to intrude on states’ jurisdiction over decisions about integrated resource planning and generation portfolios (Greenwire, Dec. 6).

So questions like how EPA should hold states accountable for emissions reductions will be a subject for future discussions, she said.

Arkansas and other states are already working to lay the groundwork for implementation plans even before EPA releases its proposed guideline, Honorable said. Speaking to reporters after the panel with McCarthy, Honorable said she had met with Arkansas’ environmental regulators and with industry to give and receive input ahead of writing its plan. She educated the environmental regulators about energy efficiency and demand response programs that utility regulators are currently implementing that might be tapped for Arkansas’ implementation plan for the existing power plant rule, she said.

She said NARUC encouraged other states to begin doing the same preparatory work, and many had. But states’ views on the rule vary broadly, and some, including Oklahoma and West Virginia, have devoted significant resources to advocating against the coming rules, arguing that they will undermine fossil fuel use.

“We are all over the map literally and figuratively, so I don’t want to paint too rosy of a picture in saying that I’m certain we can find consensus,” Honorable said.

But regulators are primarily interested in ensuring that customers have access to reliable power no matter what federal agencies propose.

“So we think it’s more prudent for us to get on top of it and to work ahead,” she said.