According to a new report from the U.S. Energy Information Administration (EIA), the carbon intensity of U.S. power generation fell 18 percent between 2016 and 2020, driven by a shift in the U.S. electricity generation mix away from coal and toward natural gas and renewables. (The “carbon intensity of power generation” measures the amount of CO₂ emitted to produce a unit of electricity.)

The report noted that all but seven U.S. states decreased their carbon intensity over that five-year period, although the amount of the decrease varied widely.

In 2020, the carbon intensity of U.S. power generation averaged 854 pounds of CO₂ per megawatthour (lbs. of CO₂/MWh), but carbon intensity varied by energy source. In 2020:

– The carbon intensity of coal in the United States was 2,274 lbs. of CO₂/MWh.

– Natural gas was less carbon intensive than coal, at 980 lbs. of CO₂/MWh.

–  Nuclear power plants and non-emitting renewables, such as hydroelectric, wind, and solar power, produce little to no CO₂ emissions.

As noted, the carbon intensity of power generation varied by state, because the mix of fuel sources used to generate electricity was different in different states. “Notably, states also receive and deliver electricity to other states, so the carbon intensity of generation in a state does not necessarily reflect the carbon intensity of the electricity used in that state,” said the report.

The states with the lowest carbon intensities of power generation either had a large share of generation from renewables or a large combined share from renewables and nuclear.

The states with the highest carbon intensities of power generation had larger shares of in-state generation from coal- or petroleum-fired power plants than the national average. Wyoming, for example, the state with the highest carbon intensity of power generation in 2020 (1,970.8 lbs. of CO₂/MWh), generated 79% of its power from coal.

Despite the large variation in carbon intensity levels, most states have been reducing the carbon intensity of their power generation. In fact, 43 states and the District of Columbia recorded lower carbon intensity of power generation in 2020 relative to 2016.

The five states with the largest reductions in carbon intensity of power generation between 2016 and 2020 were:

1. Tennessee (by 486 lbs. of CO₂/MWh)
2. Maryland (by 477 lbs. of CO₂/MWh)
3. Iowa (by 443 lbs. of CO₂/MWh)
4. Kansas (by 371 lbs. of CO₂/MWh)
5. Oklahoma (by 348 lbs. of CO₂/MWh)

In specific:

1 – In Tennessee, the share of in-state generation from nuclear and natural gas-fired plants increased. However, the share of coal-fired generation declined.

2 – In Maryland, natural gas’s share of generation increased from 15 percent in 2016 to 39 percent in 2020. Coal’s share decreased from 37 percent to 9 percent.

3 – Iowa, Kansas, and Oklahoma, all located in the central wind belt, reduced their carbon intensity as wind generation continued to displace coal-fired generation.