The figures for March are a big shift from April 2012, when the agency reported an equal share of coal and natural gas generation.

However, that was before higher natural gas prices and increased electricity demand beginning last May resulted in a usage spike by coal-fired units.

“In March 2013, coal-fired units generated a little over 130,000 megawatt-hours of electricity, while natural gas units produced nearly 85,000 megawatt-hours,” the EIA said.

In the spring shoulder season – the area of time between winter and summer when electricity demand normally drops – this year natural gas price increases reduced its share of the total generation pie below last April’s record highs.

The EIA noted that while coal’s share was up it was still well below its typical range of pre-2009 levels.

Between 2001 and 2008, the coal share on an annual basis was between 48% and 51%.

The last time coal achieved a 50% share was in 2005, although the agency’s short-term energy report projects it will hit 40% this year.