Demand for energy is largely covered by fossil fuels, namely petroleum, coal, and natural gas. Those fuels, however, are finite resources, and burning them emits large amounts of pollutants that contribute to climate change. The United States is the second largest primary energy consumer in the world, gobbling up nearly 117 exajoules every year. U.S. primary energy consumption has remained mostly unchained since the 1990s, which is in part a result of a leveling of energy demand by energy intensive sectors like electric power and transportation. In 2019, U.S. electricity end use, not counting conversion losses, fell below four petawatt hours, a decrease compared to the peak recorded the year prior.
Renewables still account for a small share of total primary energy consumption, although combined solar thermal and photovoltaic demand exceeded one quadrillion British thermal units in 2019. Meanwhile, natural gas used for electricity generation and thermal output climbed to 12.8 trillion cubic feet that same year, having notably increased since 2000.
Nevertheless, until 2050 renewables consumption in the U.S. is forecast to reach over 20 quadrillion British thermal units, nearly double the amount covered by wind, solar, and biomass sources in 2019.