The United States relies on electricity to meet a significant portion of its energy demands. Electricity generators used 31 percent of U.S. energy from fossil fuels and emitted 33 percent of the CO, from fossil fuel combustion in 2019. The type of energy source used to generate electricity is the main factor influencing emissions." For example, some electricity is generated through non-fossil fuel options such as nuclear, hydroelectric, wind, solar, or geothermal energy. The mix of fossil fuels used also impacts emissions. The electric power sector is the largest consumer of coal in the United States. The coal used by electricity generators accounted for 93 percent of all coal consumed for energy in the United States in 2019. "However, the amount of coal and the percentage of total electricity generation from coal has been decreasing over time. Coal-fired electric generation (in kilowatt-hours (kWh]) decreased from 54 percent of generation in 1990 to 28 percent in 2019." This corresponded with an increase in natural gas generation and renewable energy generation, largely from wind and solar energy. Natural gas generation (in kWh) represented 11 percent of electric power generation in 1990 and increased over the subsequent thirty-year period to represent 34 percent of electric power generation in 2019. Wind and solar generation (in kWh) represented 0.1 percent of electric power generation in 1990 and increased over the subsequent thirty-year period to represent 9 percent of electric power generation in 2019.