In 2019, natural gas will continue to be the top power plant fuel in the United States after first overtaking coal in 2016, according to a new federal report.

The Energy Information Administration's latest Short-Term Energy Outlook forecasts electricity generation from coal will dip to 28 percent in 2018 and 26 percent in 2019, down from 30 percent in 2017. Meanwhile, the report forecasts natural gas generation's share to rise to 35 percent in 2018 and 2019, compared to 32 percent in 2017.

As a result of the upward trend, "the Henry Hub natural gas spot price averaged $4.15/million British thermal units in November, up $0.87/MMBtu from the October average," the report said. "Cold temperatures and low inventory levels contributed to the increase in price."

These higher prices may not stick around. "Despite low inventory levels, EIA expects strong growth in U.S. natural gas production to put downward pressure on prices in 2019."

The agency also predicted electric utilities would burn 644.4 million short tons of coal in 2018, which would be the lowest in 34 years, and 599.7 million short tons in 2019, the lowest since 1982. That compares with 665.0 million short tons in 2017.

Nationwide, renewables make up about 10 percent of the generation mix, according to EIA. In 2019, that share is expected to rise to 11 percent. Meanwhile, changes in solar technology are behind the rise in U.S. solar generation: 212 megawatt hours per day in 2017, 268,000 MWh/d in 2018 and 303,000 MWh/d in 2019.

"In recent years, the industry has seen a shift from fixed-tilt PV systems to tracking systems. Although tracking systems are more expensive than fixed-tilt systems, revenue from the additional electricity generated by following the path of the sun across from the sky often exceeds the increased cost," the report said.