by Michael Sivak, Sivak Applied Research
Battery electric vehicles are only as clean as the energy source used to generate the electricity that powers them. The calculated relative amounts of well-to-wheels emissions of greenhouse gases from eight different energy sources are shown in the table below. (The calculations were based on the data developed by the Union of Concerned Scientists.) These results indicate that coal and oil are the energy sources leading to most emissions, and that hydro, wind, and nuclear are the energy sources leading to least emissions. On the two extremes, coal and oil result in about 176 times the emissions from hydro.
Proportional amount of emissions relative to hydro
This brief study analyzes, for each individual state, the changes from 2018 to 2020 in the use of coal (one of the two most polluting energy sources) to generate electricity. (Oil is used relatively infrequently in the United States as an energy source for electricity. In 2020, only two states used oil to generate more than 3% of the electricity: 66% in Hawaii and 16% in Alaska.) The raw data (the percentages of electricity generated from different energy sources in the individual states) came from the Nuclear Energy Institute.
This study is an update of a study that examined the changes from 2008 to 2018. Therefore, the data for 2008 are included here as well.
The results indicate that the percentage of electricity generated from coal decreased (or stayed at 0) from 2018 to 2020 in 49 states. The increases occurred only in Alaska (from 11% to 13%) and Oregon (from 2% to 3%). For the United States overall, the use of coal to generate electricity decreased from 28% to 19%.
The table below shows the top 10 states in terms of the percentage of electricity generated from coal in 2008, 2018, and 2020.
% from coal
% from coal
% from coal
The number of states that generated more than 90% of electricity from coal decreased from 2 in 2018 to 0 in 2020. Analogously, the number of states that generated more than 10% of electricity from coal decreased from 34 in 2018 to 28 in 2020.
Michael Sivak is the managing director of Sivak Applied Research and the former director of Sustainable Worldwide Transportation at the University of Michigan.