Speaking from Paris, where officials were wrapping up negotiations on an international climate pact this week, Environmental Protection Agency (EPA) Administrator Gina McCarthy offered her take on the recent shift from coal to natural gas for U.S. electric generation.

During a question-and-answer session over social media, McCarthy said the United States “had heavily invested in coal” but that “we now know, however, as China does, that it is not necessarily the path to the future. We know in the U.S. that we’re transitioning away from coal because coal is no longer marketable. We have cleaner natural gas, and we have opportunities for lower-carbon sources like renewables and using energy efficiency to lower energy demand.”

McCarthy’s comments likely ruffled feathers in coal-mining states, where President Barack Obama and his EPA have been accused of waging a “war on coal.”

The EPA’s Clean Power Plan, which targets a 32% reduction in carbon emissions from U.S. power plants by 2030 based on 2005 levels, would likely force states to further reduce their reliance on carbon-intensive coal-fired generators.

But, to McCarthy’s point on coal’s marketability, Energy Information Administration data shows coal has lost market share to natural gas over the past decade, a trend experts have attributed largely to low commodity prices.

In April, for the first time ever, natural gas surpassed coal as the leading fuel source for domestic power generation. Natural gas has since fueled the greatest share of U.S. electric generation in July, August and September, the latest month for which data is available, according to EIA (see Daily GPI, Dec. 2, Oct. 28).

Natural gas fueled 35% of total U.S. power generation in September, compared to just under 34% for coal. In 2005, roughly half of all domestic power generation came from coal.

During a breakfast roundtable in Washington, DC, this week (see Daily GPI, Dec. 10), FERC Commissioner Tony Clark talked about the transformative impact that cheap natural gas has had on electric generation.

“Just in the last year there have been some rather amazing things that have happened on the natural gas side, this intersection between gas and electricity…The trend line had been going that way for a long time. In April, we reached the tipping point, and it’s probably unlikely the trend line is going to change any time soon,” Clark said.

The Federal Energy Regulatory Commission’s focus moving forward will be on reliability as the market shifts, Clark said. Approving new infrastructure to meet ambitious timelines under the Clean Power Plan will also be of critical importance, he said.

Noting that natural gas plants “pair relatively well with intermittent resources like wind and solar,” Clark said gas is becoming a bigger part of the electric grid.

“You can’t talk about natural gas without talking about electricity, and you can’t talk about electricity without talking about natural gas,” he said.