Carnegie Mellon University

Power Sector Index as of 2021 Q2

October 19, 2021

Power Sector Carbon Index Q2 2021 Update

The Power Sector Carbon Index was created by researchers in the Scott Institute to track the progress of the United States’ transition to cleaner electricity generation. The index represents an estimate of U.S. carbon emissions created by electricity generation in comparison to the total amount of electricity generated during that period. The project uses public data to create monthly, quarterly, and yearly values, illustrating changes in the carbon intensity of US electricity generation over time. This project is supported by Mitsubishi Power.

The most recent report found U.S. power plant emissions averaged 807 lb CO2 per MWh in the second quarter of 2021, a 10 percent increase in comparison to that period the year prior. Compared to the benchmark year of 2005, the Power Sector Carbon Index lowered from 1,321 lb CO2 per MWh to 807 lb CO2 per MWh, a 39% decrease in the annual value.

The index also provides a quick look at trends in electricity generation in the US. This most recent report found that wind generation was up by 9 percent in the second quarter of 2021 compared to the prior year. Natural gas and nuclear generation saw minor changes. Hydro generation saw a decrease of 17 percent. Solar generation increased by 26 percent. Coal generation saw the greatest change, increasing by 35 percent. A full list of Q2 highlights can be found on