The cradle to grave greenhouse gas emissions of an average electric car are estimated at 28.43 metric tons (MT) of CO2e. Over an estimated 11.5 years of use (173,151 miles), an electric car will emit 2.47 MT CO2e per year, which is 13.6% of the 2018 average annual emissions for Americans. An average conventional gas car, rated at 26 miles per gallon (MPG), is estimated to emit 80.25 MT CO2e over its full lifecycle, which is 2.8 times more emissions than the electric car. Averaged over 11.5 years of use, the gas car will emit 6.98 MT CO2e per year, which is 38.5% of the 2018 average annual emissions for Americans.

Emissions of electric cars can vary significantly based on the carbon intensity of the power supply. The lifecycle emissions can vary between 8.36 MT CO2e and 45.00 MT CO2e, depending on the geographic location in the United States and the electricity mix.

Are Electric Cars Carbon Neutral?

No. Even when electric cars are powered by 100% renewable energy, there are emissions associated with manufacturing of the vehicle, end of life disposal, and manufacturing of the renewable energy infrastructure. The GREET Model (Wang, 2020) estimates 6.90 MT CO2e to manufacture and dispose of an electric car, which is 38% of the average American’s annual greenhouse gas emissions.

If the average electric car is powered by residential solar panels, it will emit an additional 1.46 MT CO2e over its lifespan (does not include battery storage). If the average electric car is powered by the average American grid electricity (EPA Power Profiler, 2020), it will go on to emit another 21.53 MT CO2e over its lifespan. While these emissions do not come from the tailpipe, they are instead emitted at the power plant.

While electric cars will often reduce emissions compared to gas cars, it is difficult to argue that an emissions reduction has occurred due to the purchase of an electric car, and thus to claim carbon neutrality. Just because you trade in your gas car for an electric car doesn’t mean you have reduced any emissions. An electric car could be claimed to be carbon neutral if a gas car is retired before the end of its useful life, and if the avoided emissions are greater than the lifetime emissions of the electric car replacing it.

The decision to purchase an electric car may even increase emissions. An electric car owner may feel less guilt about driving with less emissions per mile, and increase their total miles driven per year, which decreases the carbon benefit of switching. In some states, this would actually increase emissions. If someone does not own an electric car and decides to buy one instead of walking, biking, or carpooling, they may well be increasing their carbon emissions quite considerably.

While electric cars can be an excellent way to reduce your carbon emissions, be careful to label them as carbon neutral.

Data and Assumptions

The average electric car is based on the standard assumptions in the Greenhouse gases, Regulated Emissions, and Energy use in Technologies Model (GREET) 2 Model developed by Argonne National Laboratory. The GREET 2 Model is a Cradle to Grave Life Cycle Assessment (LCA) model that models all material and fuel inputs in a vehicle’s lifecycle.

  • The estimated lifespan of the vehicle is 173,151 miles with 2 battery replacements. The vehicle is estimated to be driven 15,000 miles per year, which results in a lifespan of 11.5 years.
  • The passenger car is equipped with a 27 kWh Lithium Ion battery and is rated at 117 Miles per Gallon Equivalent (MPGe). At the standard EPA assumption of 33.7 kWh per gallon of gasoline (US Department of Energy, 2020), this vehicle is rated at 3.46 miles / kWh, or 28.9 kWh per 100 miles.
  • The vehicle has an estimated range of 93 miles.
  • The GREET 2 Model estimates cradle to grave emissions of 2,595 kg CO2e over 3 sets of batteries at 27 kWh. Thus, batteries are estimated to emit 96.11 kg CO2e / kWh.
  • The marginal increase in the carbon footprint for a car with a larger range, such as the Chevy Bolt with a 259 mile range and 66 kWh of batteries (Chevrolet, 2020), is estimated at 3.75 MT CO2e. This would increase the carbon footprint of manufacturing and disposal by 54%.
 
Fuel emissions from the electric car are modeled separately from the GREET 2 Model. Gasoline emissions are modeled directly from the lifecycle emissions of a gallon of gasoline, which includes emissions from extraction, refining, and transport to the fuel pump, modeled in the GREET 2 Model. The lifecycle emissions of a gallon of gasoline are estimated at 11.14 kg CO2e / gallon (See Carbon Footprint of Gasoline Page).
 
The average conventional gas car manufacturing and disposal are based on the standard assumptions of the GREET 2 Model.
 
US Power Grid Emissions are based on the EPA Power Profiler. The Average US Grid carbon intensity is 947.2 lbs CO2e / MWh. The Central Wisconsin Grid (MROE) is 1678.0 lbs CO2e / MWh.
 
The carbon emissions from solar PV are based on Asdrubali et al. (2015), which reports a median carbon intensity of 29.2 g CO2e / kWh, based on 12 studies, and 36 systems modeled.
  • The study does not clearly state system boundaries, but implies a cradle to grave approach. Values reported ranged from 9.4 – 167.0 g CO2e / kWh, and thus there is a significant variability in manufacturing carbon intensity, as well as solar PV production.
  • The solar PV carbon intensity of powering an electric vehicle does not include battery storage, and thus emissions from a storage system could significantly increase the carbon footprint of the 100% solar PV powered car.
 
The 2018 average annual emissions for Americans is based on the EPA Inventory of US Greenhouse Gas Emissions Sources and Sinks 1990 – 2018 (2020), which reports 5,903.2 MMT CO2e in 2018. The average US population in 2018 is reported at 327.1 Million residents (US Census, 2018). Average emissions are estimated at 18.13 MT CO2e / resident / year.

References

Asdrubali, F., Baldinelli, G., D’Alessandro, F., & Scrucca, F. (2015). Life cycle assessment of electricity production from renewable energies: Review and results harmonization. Renewable and Sustainable Energy Reviews, 42, 1113-1122.

Chevrolet. (2020). Chevrolet Bolt EV – 2020. See Link to Source

EPA – US Environmental Protection Agency. (2020). Inventory of US Greenhouse Gas Emissions Sources and Sinks 1990 – 2018. See Link to Source

EPA Power Profiler – US Environmental Protection Agency. (2020). eGRID Power Profiler. See Link to Source

US Census. (December, 2018). 2018 National and State Population Estimates. See Link to Source

US Department of Energy – Office of Energy Efficiency & Renewable Energy. (2020). FuelEconomy.gov Top 10. See Link to Source

Wang, M. (2020). Greenhouse gases, Regulated Emissions, and Energy use in Technologies Model (GREET) 2 Model. US Department of Energy – Argonne National Laboratory. See Link to Source