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FAQ: Addressing Concerns about Electric Vehicle Well-to-Wheels Life Cycle Emissions

Posted by admin on Aug. 24, 2016  /  Electric Vehicles, Emissions & Fuel Economy  /  Subscribe 0

FAQ:

Question: Are Electric Vehicles truely cleaner than their traditional counterparts when you consider the source of the electrical power used to charge the vehicles?

Answer:  Vehicle emissions can be evaluated on a direct basis and a well-to-wheel basis. Direct emissions are emitted through the tailpipe, as well as through evaporation from the vehicle's fuel system and during the fueling process. Plug-in electric vehicles (PEVs) produce zero direct emissions. Well-to-wheel emissions include all emissions related to fuel production, processing, distribution, and use. In the case of gasoline, emissions are produced while extracting petroleum from the earth, refining it, distributing the fuel to stations, and burning it in vehicles. In the case of electricity, most electric power plants produce emissions, and there are additional emissions associated with the extraction, processing, and distribution of the primary energy sources they use for electricity production.

The life cycle emissions of a PEV depend on the sources of electricity used to charge it, which vary by region. In geographic areas that use relatively low-polluting energy sources for electricity production, PEVs typically have a life cycle emissions advantage over similar conventional vehicles running on gasoline or diesel.

In Louisiana specifically, energy produced from natural gas comprises 63.05% of the electricity used to charge PEVs, followed by nuclear power, which comprises 14.54%. According to the Alternative Fuels Data Center (AFDC) Emissions from Hybrid and Plug-In Electric Vehicles page (http://www.afdc.energy.gov/vehicles/electric_emissions.php), which provides a breakdown of electricity sources and annual emissions per vehicle type by geographic location, annual emissions per vehicle for PEVs in Louisiana is around 4,588 pounds (lbs) of carbon dioxide (CO₂) equivalent, while annual emissions per vehicle for conventional gasoline vehicles is approximately 11,435 lbs of CO₂ equivalent. 

On a national level, 33.28% of electricity is produced from coal and 32.77% of electricity is produced from natural gas. This breakdown of electricity sources results in an annual emissions per vehicle of 4,815 lbs of CO₂ equivalent for PEVs, compared to the 11,435 lbs of CO₂equivalent in emissions from conventional gasoline vehicles. As such, life cycle emissions from PEVs has generally been shown to be lower than conventional gasoline vehicles in the United States.

You may also refer to the AFDC Greenhouse Gas Emissions by Fuel Type figure (http://www.afdc.energy.gov/data/10741), which displays the results of a meta-analysis of studies looking at the greenhouse gas (GHG) emissions of a range of fuel-vehicle pathways. According to this figure, PEVs have the lowest GHG emissions, although, as mentioned previously, this varies depending on fuel mix of electricity.

For detailed information about PEV considerations, we recommend you refer to the AFDC Benefits and Considerations of Electricity as a Vehicle Fuel page (http://www.afdc.energy.gov/fuels/electricity_benefits.html). In addition, please see the AFDC Electricity page (http://www.afdc.energy.gov/fuels/electricity.html) for more general information about PEVs.

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