Carbon intensity of US power generation continues to fall

20 September 2022

From 2016 to 2020, the carbon intensity of USA power generation fell 18%, driven by a shift in the electricity generation mix away from coal and towards natural gas and renewables. The carbon intensity is a measure of the amount of CO2 emitted to produce a unit of electricity. All but seven states decreased their carbon intensity over that five-year period, although the size of the reduction varied widely from state to state.

In 2020, the carbon intensity averaged 854 pounds of CO2 per MWh, but carbon intensity varies by energy source. In 2020, that for coal in the USA was 2274 lb 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 or no CO2 emissions.

The figure varies by state because the mix of fuel sources used to generate electricity is different in different states. Notably, states also receive and deliver electricity with other states, so the carbon intensity in a state does not necessarily reflect the carbon intensity of the electricity used in that state.

The states with the lowest carbon intensities of power generation either have a large share of generation from renewables or a large combined share from renewables and nuclear. In 2020, Vermont had the lowest carbon intensity of power generation at 8.4 lb of CO2/MWh. Almost all of Vermont’s in-state electricity generation came from renewables, and Vermont brings in about 60% of its electricity from Canada.

The states with the highest carbon intensities have larger shares of in-state generation from coal- or petroleum-fired power plants than the national average. Wyoming, the state with the highest carbon intensity of power generation in 2020 (1970.8 lb of CO2/MWh), generated 79% of its power from coal.

But despite the large variations, most states are reducing the carbon intensity of their power generation. Forty-three states and the District of Columbia recorded lower levels in 2020 compared to 2016.

The five states with the largest reductions in carbon intensity of power generation between 2016 and 2020 were Tennessee (by 486 lb of CO2/MWh), Maryland (by 477 lb of CO2/MWh), Iowa (by 443 lb of CO2/MWh), Kansas (by 371 lb of CO2/MWh) and Oklahoma (by 348 lb of CO2/MWh).

In Tennessee, the share of in-state generation from nuclear and natural gas-fired plants increased as the share of coal-fired generation declined. In Maryland, the natural gas share increased from 15% in 2016 to 39% in 2020, while coal’s share decreased from 37% to 9%. Iowa, Kansas, and Oklahoma - all located in the central wind belt - reduced their carbon intensity as wind generation continued to displace coal-fired generation.

Image source: US EIA ‘Power Plant Operations report’

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