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All Charged Up, No Place to Go

Today EVs are driven much less than other cars, which has big implications for the environment.

Where in the country you drive an electric vehicle matters a lot for the environment, a point made repeatedly — both by economists (here and here) and by engineers (here and here).

You know what else matters a lot? How much you drive. This gets very little attention, but has major implications for the environmental impact of EVs.

After all, it isn’t the manufacturing of EVs that gives them their environmental edge. If anything, the copper, aluminum, and lithium required to build batteries actually make EVs somewhat more resource intensive.

Instead, the prospect for EVs as a climate change solution hinges on their ability to reduce gasoline consumption. But how much gasoline is actually saved depends, crucially, on how many miles the EV is driven and on how many miles the driver would have otherwise driven in a gasoline vehicle.

How Much Are EVs Actually Driven?

Although this seems like a straightforward question, there is surprisingly little direct evidence.  Last year in our blog, Jim Bushnell lamented that we know little about how much EVs are driven.

To shed light on this, I constructed the figure below using newly available nationally representative data from the 2017 National Household Travel Survey (NHTS).  Prior to the 2017 NHTS, the most recent NHTS was conducted way back in 2009, when there were virtually no EVs on the road.

A valuable feature of the NHTS is that respondents fill out an “Odometer Mileage Record Form.”  I took these odometer readings and divided by the age of each vehicle to calculate the average number of miles driven per year. The table below plots averages for four different types of vehicles.

fig1

Thus according to these data, EVs are driven significantly less than other types of vehicles. All-electric and plug-in hybrid vehicles are driven 6,300 and 7,800 miles annually, respectively, compared to 10,200 for gasoline and diesel vehicles, and 12,000 for conventional hybrids.

I find this pretty surprising. After all, the basic tradeoff with EVs is that they cost more to purchase than gasoline vehicles, but cost less to operate per mile. So EVs are an investment that pays off the more you drive, and consumer guides tend to recommend EVs to commuters and other people who drive a lot. I expected the opposite pattern, with EVs tending to be driven more than other vehicles.

What is Going on?

The most obvious explanation is limited range. The first generation Nissan Leaf, for example, has a range of less than 80 miles, making it impractical for roadtrips. This limited range impacts who buys EVs, and also impacts how they are used. For example, many households that own EVs have more than one vehicle, so they may just decide to leave the EV at home on high-mileage days.

Note: Today’s Nissan Leaf S has a 30kwh battery, and a 100+ mile range.   Image licensed under creative commons. https://www.flickr.com/photos/pittou2/

It is not clear how much limited range should matter for plug-in hybrids. With a plug-in hybrid you always have the option to run on gasoline, so they are not subject to the same range limitations as all-electric vehicles. Still, many plug-in hybrid vehicle drivers purchased their vehicles with the intention to use them primarily powered by electricity, so this may still have a big impact on the type of driver who buys these vehicles.

Most other potential explanations are variations on the type of person who buys an EV. For example, it could be that urban vs rural can help explain the pattern. Urban households may be more likely to buy electric vehicles, perhaps because of stronger “green” preferences in urban areas, and may also tend to drive fewer miles per year. Previous research has shown that environmental ideology is a major determinant of what kind of vehicle people buy, so the mileage pattern may simply reflect the characteristics of the places where EV buyers tend to live.

So What?

Regardless of the explanation, this pattern has important implications for the environment. In particular, it suggests that so far EVs imply far smaller gasoline savings than previously believed.

For example, a recent study called “Are There Environmental Benefits from Driving Electric Vehicles?” by Energy Institute alumni Erin Mansur and coauthors, finds that the environmental benefits from replacing a gasoline vehicle with an EV in California are worth about $2,800. Reading the fine print, however, Mansur and coauthors make this calculation assuming that all vehicles are driven 15,000 miles per year. If, instead, each EV is avoiding only 7,500 miles per year driven in a gasoline vehicle, then the benefits are half as large, only $1,400.

I’m not trying to pick on Mansur and coauthors. Other analyses on the use of EVs also rely on what seem to be overly optimistic assumptions on miles driven. Another well-known model in this space is the “GREET” model”, which assumes that EV batteries are used for a lifetime of 160,000 miles.  Moreover, federal CAFE standards use a lifetime for cars and trucks of 195,000 and 225,000 miles, respectively. All these measures seem high relative to the newly-available evidence from NHTS. For example, dividing 195,000 by 7,500 mile per year, implies an implausibly long average lifetime of 26 years.

The broader point is that mileage matters for EV policy. What we ultimately care about is reducing gasoline consumption, but current policies like the $7,500 federal tax credit treat low-mileage and high-mileage drivers uniformly. Is there some better policy that would target EVs to high-mileage drivers?  Why, yes, there is. It is called a gasoline tax. Making gasoline more expensive would incentivize EVs for all drivers, but the biggest incentive would be for people who drive a lot of miles.

roadtrip
Note: No long road trips for EVs? Image licensed under creative commons. https://www.flickr.com/photos/daxis/

 

For more details see Energy Institute Working Paper, “How Much Are Electric Vehicles Driven?

 Keep up with Energy Institute blogs, research, and events on Twitter @energyathaas.

Lucas Davis View All

Lucas Davis is the Jeffrey A. Jacobs Distinguished Professor in Business and Technology at the Haas School of Business at the University of California, Berkeley. He is Faculty Director of the Energy Institute at Haas, a coeditor at the American Economic Journal: Economic Policy, and a Faculty Research Fellow at the National Bureau of Economic Research. He received a BA from Amherst College and a PhD in Economics from the University of Wisconsin. Prior to joining Haas in 2009, he was an assistant professor of Economics at the University of Michigan. His research focuses on energy and environmental markets, and in particular, on electricity and natural gas regulation, pricing in competitive and non-competitive markets, and the economic and business impacts of environmental policy.

17 thoughts on “All Charged Up, No Place to Go Leave a comment

  1. Echoing comments by others: this is a very small sample size, of early short distance models, in a rapidly evolving market. Of course we get more benefits when we substitute more gas miles with electric miles, so we want to encourage electrification of as many miles as possible. That is happening with longer range vehicles, more fast charging, more workplace charging etc.

    On another note: we are transforming a market here. If you were to look at the cost-effectiveness of solar, or wind energy, or highly efficient appliances, in the first 3-4 years after they entered the market, you would certainly conclude that they were not very cost effective technologies. However, they are critical steps towards the necessary long range goal (in this case, ending the use of fossil fuels for transportation.)

    Last point: many of us have very happily driven gas cars for 20+ years. That’s part of the challenge to transforming this sector – it’s a very long term stock and flow problem.

  2. Since over 90% of driver mostly drive within 40 miles of their home, I think the researchers actually need to verify their thesis is true. Also, most families have two cars and if the primarily use the EV for most of their local driving and just utilize their SUV for longer driving, it still may be a huge net benefit. So I am skeptical of making any conclusions till we see much more data. – Scott Sklar, Adjunct Professor, The George Washington University (GWU)
    Scott Sklar, Adjunct Professor
    and Director of Sustainable Energy at the Environment &
    Energy Management Institute (EEMI) and Acting
    Director, GWU Solar Institute
    The George Washington University (GWU)
    https://eemi.seas.gwu.edu. https://solar.gwu.edu/

  3. An additional consideration: the vast majority of car trips are short ones, less than 20 miles. Some relatively old Federal data can be found here: https://www.fhwa.dot.gov/policyinformation/pubs/pl08021/fig4_5.cfm Two factors can make those short trips more polluting for gasoline-powered cars: the short trips are more of the stop-and-start variety around town, generating lower gas mileage per trip; and the initial starting of a cold gasoline-powered engine generates a disproportionately large amount of pollution. How might the analysis change if we factored in number of trips and pollution per trip?

  4. Are you suggesting that those who get EVs should drive more! No.
    Do EVs really ‘cost’ less per mile in energy? I have not looked at ToU residential rates, but if you charge at a public charging station typically the charge is 3-5c/ minute for L2 at EVGo station near me. It takes about 2hrs 20 min to fully charge a BMW 330e – which claims an electric range of 24miles, but delivers 16. So cost us $4.50 for say 20 miles. I get 35 mpg without station recharging, ie just in hybrid mode. So MY experience is crossover at about $8 per gallon gas.

    LCA must also include disposal impacts, not just production and use phases. Disposing the toxic chemicals and metals of EV systems is a heavier environmental burden.

    Having said all that: it feels good to drive in E mode – and know you are not emitting toxic exhaust in the neighborhood!! 😔

  5. It looks like this analysis neglects to account for leasing of EVs (especially lower-range BEVs). The California Air Resources Board has done some analysis of this and found that annual mileage is (unsurprisingly) correlated with the lease mileage cap. https://www.arb.ca.gov/msprog/acc/mtr/appendix_g.pdf (page G-20). ARB shows data for a 12k miles/yr cap, but a lot of the lowest cost lease deals are for 10k (or even less). http://ev-vin.blogspot.com/ The per mile costs for exceeding the lease limits can be high, so it wouldn’t be surprising if a good portion of BEV drivers were matching their driving to these limits. It’s the economically rational choice.

    Since many of the lower-range EVs (and a good number of PHEVs) were sold on leases while the fraction of gasoline cars leased is much lower, it seems that lease mileage caps could explain at least part of the VMT effect you are seeing.

  6. I agree with Jim Lazar about the problems of drawing conclusions from an examination of average mileage data drawn from the current on-the-road fleet of EVs.

    I would also point out that the idea that EVs are more resource intensive than conventional vehicles misses several key points. Yes, electric batteries use more of certain elements, such as lithium and cobalt, than you would find in an ICE vehicle. At the same time, they use less steel and related alloys, because of the lack of an engine and transmission. Ultimately, the evidence from life cycle analysis studies on conventional and electric vehicles is pretty definitive: for both EVs and ICE vehicles, the environmental impacts are, as a rule, dominated by the use phase rather than production. For most of the environmental metrics of interest, across most relevant scenarios, EVs have a significantly lower footprint across their life cycle than conventional vehicles due to their significantly better energy efficiency and the ability to utilize low-impact sources of electricity.

    I absolutely agree that we should take materials consumption into account when evaluating environmental policy. In the case of EVs, this claim has been repeatedly examined in the LCA and industrial ecology literature. In most cases, especially where regional or global impacts like air and surface water pollution are concerned, EVs are generally lower-impact than conventional alternatives.

    I would also point out that assuming 26 years is “implausibly long” fundamentally applies expectations about vehicle reliability which are based on our history with ICE vehicles. We don’t know how long EVs will last once they’re in wide-scale use. There are theoretical reasons to believe they may last significantly longer than ICE vehicles, due to fewer moving parts and less risk of systems damage from irregular maintenance or inadequately monitored fluids. While I agree that we shouldn’t base policy on an assumption of a longer lifespan for EVs, neither should we dismiss it out of hand.

  7. If it’s the case that EVs are being used primarily for short trips, it’s worth noting that fuel consumption and pollution are greater than the overall average for conventional vehicles.

  8. A couple points – yes, it’s long been clear that EVs are low mileage vehicles for those who commute relatively short distances and want carpool passes in California. Only time will tell if hybrid drivers will give up our 40-50 mpg vehicles with essentially unlimited range due to quick charging with gasoline. Secondly, i disagree on your Prop 6 view. The legislature has used fuel taxes as a general fund and pet project piggy bank and it’s irresponsible to support that toxic behavior. Yes on 6.

  9. Yes, the AVERAGE miles/year for existing EVs is low, but that’s mostly because the Existing EV fleet is dominated by early Nissan Leaf vehicles, which have limited range (but are a great choice for a person with a short commute.)

    But newer EVs have more range. Even the new Leaf has 151 miles of range. The Chevy Bolt has 238 miles of range. Teslas are available with up to 400 miles of range.

    It might be more useful to measure the average annual mileage of existing LONG RANGE electric vehicles to have a guide to the future. This means looking at Teslas and Bolts, not at Nissan Leafs. At the extreme end, there are Teslas being used as taxis and shuttle vehicles in California, Seattle, and Amsterdam. Some with up to 17,000 miles per MONTH and 400,000 miles total under their belts. https://www.tesloop.com/blog/2018/7/16/tesloops-tesla-model-s-surpasses-400000-miles-643737-kilometers

    There is a lot at play here. Long-range EVs are still expensive, and the tax credit is only relevant to people with taxable income. Therefore, they are mostly driven by people with above-average income, who may have the flexibility in their lives to not drive too much.

    That is changing: you can buy a used Leaf with low miles for under $10,000, and a neighbor of mine uses hers to commute to her part time job as a teacher.

    I think this post is taking a two-dimensional snapshot in a four-dimensional world; time will bring change.

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