Electric Vehicle Emissions: 4 Lessons Learned from the Literature

, , former engineer and Kendall Science Fellow | February 6, 2014, 10:58 am EDT
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Some people claim electric vehicles (EVs) emit more pollution than conventional vehicles, but based on what? Certainly not based on published literature.

I’ve recently been reading a lot about lifecycle impacts of EVs compared to conventional vehicles and find that a resounding majority of the peer-reviewed academic literature suggests that EVs usually emit less than conventional vehicles. Of course, this depends on many assumed factors in each study (like the electricity grid mix and the vehicle’s lifetime), which I’ve outlined below. Suffice to say: EVs are typically a great way to go for reducing vehicle emissions.

An engineer studying emissions in an engine research facility. Credit: Argonne National Laboratory

An engineer studying emissions in an engine research facility. Credit: Argonne National Laboratory

1. Vehicle lifetimes matter.

The lifetime of vehicles varies quite a bit, but the average is about 130,000 miles (or 210,000 km) according to EV lifecycle assessment (LCA) studies I reviewed, with a range of 93,000 miles to 180,000 miles. The vehicle lifetime is not just how long a single owner has the vehicle, but any and all of the owners combined. It’s basically the usable lifetime of the vehicle.

With a shorter lifetime, gasoline vehicles tend to look better in terms of emissions, but with a longer lifetime EVs tend to look better. Why is this? Well, EVs tend to create more greenhouse gas (GHG) emissions when they are manufactured because of the battery production. However, gasoline vehicles produce more GHG emissions when you drive them. As always, there’s a tradeoff: this time between more upfront emissions from the production of EVs, or more emissions from the use of the vehicle from a gas-powered car’s combustion.

2. Electricity emissions are the majority of the lifecycle emissions associated with an EV.

Although a lot of studies differ in the actual amount of pollution they report EVs emitting over the lifetime of the vehicle, all of them agree it’s the use of the EV where most of the emissions come from. UCS’ own State of Charge report estimates those emissions.

The results depend on a lot of variables, but our report concludes that EVs produce less emissions than the average compact car everywhere and are cleaner than even the most efficient hybrids for nearly half of Americans. And it can get even better as we reduce the carbon intensity of the electricity grid by adding more renewable energy like wind and solar.

3. The vehicle’s end-of-life has minimal impacts.

The end-of-life of an EV is difficult to determine, mostly because the EV market is still new enough that there aren’t a lot of vehicles at the end of their life. Most studies speculate what will happen when the vehicle is no longer useful, but believe that it is not nearly as important as the use phase or manufacturing phase of the lifecycle. The conservative approach is to assume that all the emissions impacts are directly related to the first use, the vehicle. Even so, EVs still reduce greenhouse gas emissions more than conventional vehicles in the studies I reviewed.

4. Batteries are the main contributor to emissions differences in manufacturing EVs compared to gas vehicles.

Most studies, due to lack of data available, model EVs as generic vehicles with batteries added on during the production phase. How much the battery production contributes to the overall LCA varies by study, but I’m very interested in the battery production impacts. Stay tuned for more information on how the battery production and other manufacturing GHG emissions impact the total LCA of EVs.

Featured image courtesy of Steve Jurvetson.

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  • Richard

    Thanks from me, too.

    I am a pleased owner of a Prius since 2008. While I plan to continue to drive my Prius for many more years to come, I hope to purchase an EV in the future. This is because I am basically a city driver and retired. At this point I drive less than 10,000 miles a year. So, an EV can meet my needs quite readily.

    It’ll be interesting to see how battery production and technology changes in the years to come.

    • Rachael Nealer

      Thanks so much Richard! That’s great to hear. Make sure to stay tuned. I’ll have many more EV blogs to come.

  • Thank you for the informative article! A brief note for the editor: clarifying what the acronyms GHG and LCA stand for is helpful for non-specialist readers who don’t take the time to figure it out from the article’s content.

    • Rachael Nealer

      Thanks for pointing that out, Damon. We will correct those. And thanks for reading the post!