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Carbon emissions from generating electricity for electric vehicles vary greatly across the individual US states

by Michael Sivak, Sivak Applied Research

The overall advantage of battery electric over gasoline vehicles, in terms of well-to-wheels emissions of greenhouse gases, has been well documented. However, the emissions of electric vehicles depend greatly on 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 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.

Energy source Proportional amount of emissions relative to hydro
Coal 175.9
Oil 175.9
Natural gas 87.9
Geothermal 16.5
Solar 14.6
Nuclear 2.2
Wind 2.0
Hydro 1

Individual US states vary greatly in the distribution of the energy sources for generating electricity within their borders. For example, the dominant source in Rhode Island is natural gas (90.9%), in West Virginia it is coal (90.8%), in Washington it is hydro (64.6%), and in New Hampshire it is nuclear (56.5%). Therefore, this study analyzes state-to-state variation in the corresponding emissions. The raw data (the percentages of electricity generated from different energy sources in the individual states in 2021) came from the Nuclear Energy Institute.

According to the EIA, “the plants that are the source of biomass for energy capture almost the same amount of CO2 through photosynthesis while growing as is released when biomass is burned, which can make biomass a carbon-neutral energy source.” Therefore, biomass as energy source was assumed to produce no additional carbon emission. The category labelled “other” among the energy sources (less than 1% in the total United States) was disregarded.

The table below lists the 5 states with the most emissions and the 5 states with the least emissions. (The entries are on the same scale as in the table above.)

Rank State Proportional amount of emissions relative to 100% hydro
1 West Virginia 163.9
2 Kentucky 143.1
3 Missouri 139.2
4 Hawaii 137.1
5 Wyoming 132.3
47 South Dakota 25.3
48 Maine 24.4
49 Idaho 24.4
50 Washington 18.8
51 Vermont 2.5

This analysis indicates that, for the two extreme states, the indirect emissions from electric vehicles powered by the electricity produced in West Virginia are, on average, 66 times greater than the indirect emissions from electric vehicles powered by the electricity produced in Vermont. The electricity generation fuel shares in these two states are shown in the table below.

Energy source Electricity generation fuel shares (%)
West Virginia Vermont
Coal 90.8 0
Oil 0.3 0.2
Natural gas 4.1 0.1
Geothermal 0 0
Solar 0 8.8
Nuclear 0 0
Wind 2.5 15.7
Hydro 2.3 50.0
Biomass and other 0.1 25.2

Michael Sivak is the managing director of Sivak Applied Research and the former director of Sustainable Worldwide Transportation at the University of Michigan.



Here in CO over the past week, zero-carbon, sustainable, renewable generation varied from about 5% during a brief dunkelflaute to 85% during a couple of sunny and windy periods. In areas with nuclear, peak demands are usually met with fossil peakers. Timing is everything. And it's not difficult to time the charging of EVs to coincide with low emissions generation. Lots of EVs out there with 70 kWh batteries, using 10 kWh or less on a given day. Or conversely to come home and blithely plug in at 6PM as the sun sets during the summer peak period.


@fred, you are absolutely right on the timing and battery size.
With large batteries, it should be possible to charge most of the time in times of high renewable penetration.
The problem is getting people to a: care about it and b: actually do it.

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