Since 2007, the number of states where coal was the most prevalent electricity generation fuel has fallen as natural gas, nuclear and hydroelectricity have gained market share.

In 2017, coal provided the largest generation share in 18 states, down from 28 states in 2007, according to the Energy Department's Energy Information Administration (EIA). Natural gas had the largest share in 16 states, up from 11 in 2007. Petroleum remained the largest generation share in only one state — Hawaii — providing 62% of the state’s electricity generation in 2017.

For the United States as a whole, natural gas provided 32% of total electricity generation in 2017, slightly higher than coal's 30% share.

EIA says that nuclear power plants provided the largest electricity share in nine states, up from six in 2007. Hydroelectricity is the most prevalent electricity generation source in six states, up from four in 2007. Hydro is the only renewable energy source with the largest share in any state, but EIA says that may soon change with the continued addition of wind turbines in states such as Kansas and Iowa.

Source: EIAIn the 10 states that were primarily generating electricity from coal in 2007 but not 2017, five are now primarily generating electricity from natural gas and five primarily from nuclear. These changes have occurred as coal-fired power plants have retired or been used less and as natural gas-fired power plants have been built and used more nationwide. EIA says that only one nuclear power plant was built in those years — Watts Bar Unit 2 in Tennessee — but some other nuclear power plants across the country have completed uprates to their existing nuclear generators.

In 2007, nuclear power provided 81% of Vermont’s electricity generation. Following the 2014 retirement of the state’s sole nuclear power plant, Vermont Yankee, the state’s nuclear share fell to zero, and hydro and biomass became the state's top two generation sources.

In New Jersey, the addition of natural gas-fired generators led natural gas to surpass nuclear in 2015. More than a quarter of New Jersey’s currently operating natural-gas fired capacity came online from 2009 through 2016.

Among the 11 states where natural gas was the most prevalent electricity generation fuel in 2007, all were still using mostly natural gas in 2017, except Maine. There, lower utilization of the state’s natural gas-fired generators resulted in hydroelectricity surpassing natural gas as the state’s most common electricity generation source in 2017.