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How Do Lifecycle Carbon Emissions from Electric Vehicles Compare to Conventional Gasoline-powered Vehicles?

Ask a Scientist - January 2014

L. Engle of Pocatello, Idaho, asks "Are the lifecycle carbon emissions from a typical electric vehicle greater than that of a comparable conventional gasoline-powered vehicle?" and is answered by Dr. Rachael Nealer, a Kendall Fellow in the Union of Concerned Scientists’ Clean Vehicles Program.  

This can be a tricky question to answer given there are so many variables, but current research says that the lifecycle emissions from an EV are lower than that of a comparable gasoline vehicle. When modeling each of the vehicles’ impacts, studies assume the vehicles share common components: same chassis, same body, same interior. The main difference between an EV and a conventional vehicle is the EV stores energy from the electric grid in a battery and uses it instead of burning gasoline.

The first stage of a vehicle’s lifecycle includes extracting and fabricating the materials that make up the vehicle, transporting those materials to the factory, and then manufacturing and assembling it. The biggest difference when comparing EVs with conventional vehicles are the processes associated with manufacturing the EV’s battery. Because of the additional global warming emissions released while producing, assembling, and installing an EV battery, the EV is responsible for more pollution than a conventional vehicle when it reaches the dealership, as long as the electricity source for production is the same for both, say a coal- or natural gas-fired power plant. 

The next stage of a vehicle’s lifecycle is after it’s sold and hits the road. This is called the “use” phase. Most studies assume that a typical vehicle will last about 162,000 miles, which amounts to 13,500 miles per year for 12 years. Over that time, a typical conventional vehicle will pollute much more than an EV, which is responsible only for the pollution emitted from the source providing its electric charge. Regardless of the source of the EV’s electricity—be it a coal-fired power plant, nuclear plant, solar array, or wind farm—it will pollute less than a typical conventional gas-powered vehicle over that 162,000-mile lifespan, as shown in UCS’s 2012 State of Charge report. There will be some additional emissions from maintaining an EV, but they are expected to be minimal, or similar to that of a conventional vehicle, compared with other emissions during this phase of the lifecycle.

Finally, there’s the vehicle’s end-of-life stage when it can be salvaged for parts and crushed for a landfill. Most studies conclude that carbon emissions from recycling and disposing unusable parts from an EV are negligible, but there is not much data given EVs are still relatively new. 

EVs do produce more emissions in the manufacturing phase, but in most cases the emissions savings from driving the EV more than makes up this difference. Taking the two vehicles' entire lifecycles into account, making and using an EV in the United States produces less global warming emissions than a conventional gasoline-powered car.

There are some critics who claim EVs pollute more, but they often use shorter vehicle lifetimes, sometimes as little as 50,000 miles, to make a misleading comparison. If both the EV and the conventional vehicle only go 50,000 miles, then yes, because of the extra energy needed to manufacture the EV battery, the EV may generate more pollution than a conventional vehicle on our current electric grid mix. But today’s cars typically go more than three times that far, so those comparisons are not realistic. In fact, as electric utilities transition from coal to low carbon energy alternatives, EVs will be that much cleaner.

Rachael Nealer joined UCS in September 2013 as a Kendall Science Fellow in the Clean Vehicles Program. Before coming to UCS, Dr. Nealer worked for the U.S. Environmental Protection Agency where she modeled the lifecycle greenhouse gas emissions associated with biofuels for the Renewable Fuels Standard.Dr. Nealer received her joint Ph.D. in civil and environmental engineering and engineering and public policy from Carnegie Mellon University.





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