Per capita CO2 emissions from primary energy consumption decreased in every state from 2005 to 2023, according to recently released data in our State Energy Data System. Total energy-related CO2 emissions in the United States fell 20% over that time, and the population grew by 14%, leading to a 30% decrease in per capita CO2 emissions.
CO2 emissions across the country primarily declined because less coal was burned in the electric power sector. Increased electricity generation from natural gas, which releases about half as many CO2 emissions per unit of energy when combusted as coal, and from non-CO2-emitting wind and solar generation offset the decrease in coal generation. Looking ahead, our Short-Term Energy Outlook forecasts a slight 1% increase in U.S. total CO2 emissions in 2025, in part because of more recent increased fossil fuel consumption for crude oil production and electricity generation growth.
Our state energy-related CO2 data represent emissions from primary energy consumption of fossil fuels (petroleum, natural gas, and coal) for all sectors. We count CO2 emissions released at power plants in the state where they are located, even if the electricity generated is sent across the grid for use in other states or countries. Similarly, we account for transportation CO2 emissions in the state where fuels are sold to end users, even if the vehicles, boats, or planes later travel across state or international lines.
Maryland led all states with a 49% reduction in per capita CO2 emissions from energy consumption between 2005 and 2023, as the state's total CO2 emissions fell 43% and population grew 11%. In 2023, Maryland had the lowest per capita CO2 emissions of any state, at 7.8 metric tons of CO2 (mtCO2), which is the second lowest in recorded data beginning in 1960. The District of Columbia has lower per capita CO2 emissions than any state and tied its record low of 3.6 mtCO2 in 2023.
In Maryland, coal and natural gas accounted for 56% and 4%, respectively, of in-state electricity generation in 2005, but coal and natural gas shares nearly reversed to 5% and 41%, respectively, in 2023. During the same period, new solar and wind generation came online, and the combined generation mix shift resulted in a 74% reduction in Maryland's total electric power sector CO2 emissions. Similar coal retirement and replacement trends occurred in each of the states with the largest reductions in per capita CO2 emissions from 2005 to 2023.
