Sorry, Buying A Prius Won't Help With Climate Change

Hybrid and electric car sales may help automakers' bottom line, but they might not do much to mitigate upcoming environmental disasters.

There are lots of good reasons for buying an electric car, from cutting your gas bill to feeling good for helping out with smog. But climate change? Not really.

Though Priuses and Leafs are associated with greener living, it turns out they do little planetary good, according to a new study. When you quantify the economy-wide impact of electric vehicles, measured in greenhouse gas pollutants, it's basically a wash. From a climate perspective, you might as well keep your old sedan.

Researchers look at 108 scenarios for adoption of hybrids, plug-in hybrids, and full battery electric vehicles between now and 2050, using combinations of five parameters: oil prices, natural gas prices, vehicle battery costs, government incentives for alternative fuels, and a possible federal cap on CO2 emissions. So in one scenario, for example, they assumed high oil prices, low battery costs, no cap on CO2 in 2030.

Even assuming electric vehicle adoption rates approaching 50%, the effect in carbon emissions was negligible, they found. "The model results do not demonstrate a clear and consistent trend toward lower system-wide emissions as [electric drive vehicle] deployment increases," the paper says.

The researchers cite two main reasons. One is that lower tailpipe emissions are offset by the impact of increased electricity generation need to charge the cars' batteries, even assuming a lot of renewable sources of power are used. The second is that any given person's own vehicle emissions are relatively modest—adding up to no more than 20% of their own total carbon emissions.

The research isn't the first to conclude that increased power production minimizes the CO2 benefits of EVs, says one of the authors, Joe DeCarolis, an assistant professor at North Carolina State. But the work is unusual in taking a system-wide view, including factors like oil prices.

DeCarolis stresses that the model doesn't account for improvements like local air quality. But it does have implications for climate policy, suggesting that, if the goal is to cut carbon emissions, the government would be better off introducing a carbon cap—which produces the biggest drop in CO2, sulfur dioxide, and nitrogen oxide according to the model—than encouraging people to buy EVs. New car sales may help Detroit and Toyota, but they don't do squat for global warming.

[Image: Prius via Flickr user Toyota UK]

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  • A few other clarifications. The energy system model deploys mainly electric vehicles by 2050, so the article's focus on the Prius is largely irrelevant. Also, we did not look at "government incentives for alternative fuels", but rather a renewable portfolio standard, which requires a minimum share of renewable electricity. Finally, light duty vehicles represent approximately 20% of total US emissions, not an individual's emissions.

    It pays to read the paper, not just extrapolate from a press release.

  • The conclusions in our paper are much more nuanced. With regard to policy implications, we say the following: "Therefore, it is not enough to simply incentivize the purchase of EDVs and wait for emissions benefits to accrue. The emissions benefits -- if any -- will depend on a broad set of future conditions. Therefore, public policies that target EDV deployment should be formulated, reviewed, and revised with careful attention paid to evolving changes to the broader energy system over time. If the primary objective is to reduce emissions, policy makers should focus on implementing targeted emissions policy rather than the promotion of specific technologies or fuels." I don't view this as an indictment of electric drive vehicles. I told Ben via email that much more work needs to be done, and that uncertainties associated with projections to 2050 are very large.

  • I am the senior author of this paper.

    This article goes way beyond the conclusions of our journal paper. Three quotes from the article that I strongly disagree with: (1) "it turns out they do little planetary good", (2) "From a climate perspective, you might as well keep your old sedan", and (3) "New car sales may help Detroit and Toyota, but they don't do squat for global warming". Also, I have no idea where the block quote came from "Even assuming electric vehicle adoption rates approaching 50%, the effect in carbon emissions was negligible." It is not in our paper or press release.

  • Thanks for clarifying. We've had Priuses for several years, and now have one and a Mitsubishi EV. A rough guess is that we have racked up a total of 400,000 miles on these vehicles. The math says that an average of 45 mpg, we've avoided about 7,000 gallons of gasoline as opposed to 25-mpg gas-fueled autos. At 20 pounds of CO2 per gallon, that's 140,000 pounds (70 tons) of carbon dioxide avoided, for a single family. I don't believe that is insignificant on the household scale. Too bad the author created a meme that will live on in the conspiracist propaganda mills.

  • William J. Hamilton

    I am quite certain our Prius had far less impact on the planet this evening than the five thousand pound extended cab pickup crowding us on the road. I took transit to work this morning, but the ride home required crossing 12 lanes of traffic. I'm legally blind. I have a reflective vest and blinker lights. However it was foggy tonight and my left foot really hurts because I stepped off a bus into a pot hole two weeks ago because the area wasn't lighted and my lights and vision didn't work well enough. I think cars suck and we got as little car as we could live with. We use it as little as we can. I understand that brave young men and women are dying in the middle east and every drop of petrolium products we consume contributes to those deaths. I run the local pro public transit organization. www.busec.org A serious commitment to transit by the environmental community would help a lot. That means getting your body on a bus, a lot.

  • Ruben Anderson

    Neither gasoline cars nor electric cars are good for the ecosphere. They are less bad, but they aren't good. Walkable neighbourhoods are good.

  • John Hartshorn

    Current technologies will allow us to reduce CO2 from electrical generation by around 90% by mid-century. Even using the current mix of generation, about 25% CO2 free, the rest divided 50-50 between gas and coal, a car like the Prius produces only a third to a half of the emissions of a similar vehicle with an internal combustion engine. We can fully electrify all road and rail transportation if we are willing to invest in the electrification of roads instead of relying on bulky, expensive batteries for most energy. With all major roads electrified it would require only a small battery pack to deal with local roads for 50 miles or so at a time, substantially reducing the cost of electric vehicles as well as improving performance and handling. The article neglects all this to focus on one set of scenarios that takes no account of the likely evolution of energy systems.

  • David Swartwood

    Wow this is taking this study WAY out of context. His point was that if we had a Carbon Cap nationwide that electric cars would not provide a benefit as we would go right up to the cap no matter what. He never said that electric cars don't lower pollution taken individually. Just like recycling is great but really only a stop gap until we start use something more sustainable than plastic.

  • Gregory Lemieux

    The largest problem with this study is that I can’t seem to find where they define the assumptions in emissions due to fossil fuel generation (i.e. the well-to-pump emissions). They spend an awful lot of time talking about electricity generation emissions, but not about the emissions in refining gas, mining, or other sources that are a large part of emissions as well. If I remember correctly, EVs are already lower emissions from cradle-to-grave compared to ICEs given the ongoing emissions cost of generating fuel. Limiting the paper to only comparing power plant emission against tail-pipe emissions probably skews the results drastically in favor of ICEs.

    A better review of the paper: http://www.slate.com/blogs/future_tense/2014/01/27/north_carolina_state_study_electric_cars_won_t_save_planet_but_they_ll_help.html

  • Edison Santos ES Emprendimiento Sostenible

    Don't think so. Fossil fuels industry may absolutely agree with you. So now you dare to say that burn fossil fuels don't affect Climate Change? Please, if transportation is the 2nd biggest Global co2 emissions sector. Take for example Dominican Republic, our Electric Generation mix emit 0.64 kg of co2 per kw of energy we produce, I have and electric vehicle that gave me 60km per charge and only consume 1.3 kw per charge, that 0.83 kg of co2 vs the 9.6 kg of co2 it will be with gasoline for the same 60km based on the 150grs per km. That's 91% more clean or carbon neutral that gasoline. Or my Prius that give me almost 4 times the mileage that my past “sedan" you promote used to gave to me proportionally with 4 times less gasoline and co2. We have to be careful with what kind of sources we believe in, because some of them respond to some unsustainable Interest. I respond to an specific Interest too, the one call “Sustainable Development", CEO of a better future!