Over the past 15 years, the electricity generation mix in the United States has shifted away from coal and toward natural gas and renewables, resulting in lower CO2 emissions from electricity generation, according to the U.S. Energy Information Administration (EIA).
In 2019, the U.S. electric power sector produced 1,724 million metric tons (MMmt) of CO2, 32% less than the 2,544 MMmt produced in 2005.
Lower CO2 emissions have largely been a result of a shift from coal to natural gas in the electricity generation mix. In 2005, coal made up 50% of U.S. electricity generation; that share declined to 23% in 2019. Conversely, natural gas increased from 19% of total generation in 2005 to 38% in 2019.
Coal has more carbon content per unit of energy, while natural gas-fired generators are more efficient and produce electricity with significantly less energy input than coal, which also helps lower emissions.
The EIA report also notes that of the 819 million metric ton decline in CO2 emissions from 2005 to 2019, approximately 248 million metric tons (30%) of that decline is due to the increase in renewable generation. In comparison, almost 532 million metric tons (65%) of the decline in CO2 emissions is attributable to the shift from coal-fired to natural gas-fired electricity generation. EIA says decreased petroleum-fired generation largely influenced the remaining decrease in CO2 emissions.