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Do EVs Matter? Four Takeaways from a Study on Electric Vehicle Emissions

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A recent paper from North Carolina State University researchers posed the provocative question: “How much do electric drive vehicles matter to future U.S. emissions?” The article, published in Environmental Science & Technology, attempts to answer this question by examining the possible interactions between our national electricity and transportation system. As you can imagine, this is a complex question with an equally complicated set of answers. However, their finding that sales of electric vehicles (EVs) won’t necessarily lead to lower overall emissions has received the most attention. But does it mean electric vehicles don’t reduce emissions? No, it doesn’t: in fact one of the authors said they didn’t intend to show EVs have no impact on emissions in an interview with Slate.

So what can we take away from this study? The authors used models of transportation and electric generation emissions and tested several assumptions about future prices and policies: the price of oil, the price of natural gas, the cost of EV batteries, and whether the U.S. has policies on renewable energy and/or CO2 policies. For all the scenarios (108 in total), they vary the characteristics described above and calculate the least cost transportation and electrical generation options and the resulting emissions (CO2, SOx, NOx) of that scenario in 2050. The model predicts EV market share ranges from 0 to 46%. Below are some of the interesting takeaway messages of the paper from my perspective.

1. EVs reduce the costs to comply with policies that limit CO2 emissions.

When the authors model a policy requiring a 40% reduction of  CO2 by 2050 (based off 2010 emissions), EVs reduce the cost of compliance. This means EVs are an effective way to reduce CO2 emissions for the combined electricity and transportation sectors. That said, the authors suggest their results do not show a correlation between EV deployment and emissions reductions. However, the simple cap on total emissions means that when the model generates emissions savings from EVs, emissions are allowed to grow in other parts of the model—potentially masking EV emissions savings. At UCS we believe a larger CO2 reduction is necessary, which is a major focus of our Half the Oil campaign for the transportation sector. A higher CO2 reduction requirement would probably make EVs look more desirable and increase their market share, though a sweeping carbon policy may be difficult to implement in today’s world.

Nissan Leaf at the 27th Electric Vehicle Symposium in Barcelona Spain November 2013.

Nissan Leaf on display at the 27th Electric Vehicle Symposium in Barcelona Spain November 2013. Source: R. Nealer

2. Lower battery costs would increase EV deployment.

This is not a shocking result. We already know that EVs are much more favorable when they cost less. This paper emphasizes the need to continue to reduce those costs. The Joint Center for Energy Storage Research, funded by the Department of Energy, is working to do just that; their goal is to develop batteries that are five times more powerful and five times cheaper than current technology within five years, helping make EVs more affordable.

3. EVs are an important piece of a suite of solutions.

The authors suggest EVs don’t directly reduce emissions in 2050, suggesting that other factors (like CO2 policies) play a larger role in reducing emissions. At UCS we advocate for many policy and technology solutions that will reduce emissions even in the absence of broader CO2 policy. Within our clean vehicles program our Half the Oil campaign calls out a number of solutions, including better biofuels, electric vehicles, and more efficient cars and trucks. EVs are part of a longer term, multi-faceted strategy to reduce emissions. Focusing on a single solution and ignoring the rest is not going to be beneficial in the long-run.

4. The model results show, on average, more EVs equal greater emissions reductions.

Of the 108 combinations of future policies and technologies in the study, there are 6 that have no EV deployment and 22 that have high EV deployment (42% market share). When I looked at the average emissions of the high EV deployment combinations, there is a reduction of CO2 by 23%, SOx by 11%, and NOx by 11% compared to the average emissions with no EV deployment—though these results have significant variability.

Overall, the authors do a good job of starting the discussion about the interactions between the electricity and transportation sectors. As difficult as it is to model such large and uncertain systems into the future, UCS believes EVs have a significant role to play in reducing U.S. emissions. How much EVs reduce emissions depends in part on decreasing battery costs and the choices the U.S. makes about lowering the emissions of the electricity grid.

Posted in: Vehicles

About the author: Rachael Nealer is an engineer and Kendall Science Fellow exploring the lifecycle environmental impacts of advanced vehicles, specifically hybrid-electric, plug-in electric, and fuel cell vehicles. See Rachael's full bio.

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