Electric Cars: Are They Really A Dire Emissions Threat?

Follow John

2012 Toyota Prius Plug-In Hybrid - production model

2012 Toyota Prius Plug-In Hybrid - production model

Enlarge Photo

This seems to be our time for debunking dumb stories about plug-in electric cars.

First, we had to educate a Forbes columnist (and oil-industry consultant) about how the auto industry works.

Now, it's time to offer some gentle guidance to all those journalists who covered last month's release of a study from the Norwegian University of Science and Technology that says, in essence, that plug-in cars are worse emitters of carbon dioxide on a wells-to-wheels basis than gasoline or diesel cars.

We were prompted by a piece on Jalopnik, but it was also covered in many other places.

(We note with amusement that the Popular Mechanics coverage hat-tips a gent who lists Chevron and Mobil as current employers. Uh huh.)

Data is good

In any case, we like data, we tend to like university studies, and we think that, if peer reviews of the Norwegian report hold up over time, it's a valuable contribution to the discussion.

But like all knowledge, there's some important context required to give media audiences a true sense of what it means.

The coverage of the Norwegian report highlights the reductionism often found in science coverage by quick-hit journalists, who take 20 minutes to cover the complex topics found at the intersection of energy policy and the global auto industry.

In almost all the coverage, there are a lot of qualifiers and caveats that reporters neglect in their eagerness to delineate the black and the white.

So here goes.

Norway: Not the U.S.

First, and by far most importantly, the study is more applicable to Europe than to the States.

Electric power plant outside Ithaca, New York

Electric power plant outside Ithaca, New York

Enlarge Photo

The study looks at "the present European energy mix," which is vastly different than the various mixes found in the U.S. (Norway has both a very positive attitude toward electric cars and strong government incentives for their adoption.)

Across Europe, the dominant fuel for electric grids is largely coal (with the exception of France, which has a huge amount of nuclear generation).

And in Europe, the baseline cars for comparison are much more efficient to start with: say, 40 mpg on average vs. 25 mpg for the States. Worse, differing test cycles between Europe and the U.S. make head-to-head comparisons quite challenging.

But about those grids: In the U.S., many electric utilities use more natural gas and--in some places--more renewables, including not only wind and solar but also hydro.

Thus the amount of carbon dioxide produced per kilowatt-hour across different U.S. grids varies by more than a factor of two, which makes it dangerous to generalize about the effect of electric cars.

Beware broad conclusions

And that's the biggest problem with the coverage, in our view: What's applicable in a comparison of far more fuel-efficient cars against electrics charged on European grids may be quite different from less efficient U.S. vehicles compared to plug-ins used in states with much cleaner grids.

A single coal plant in a particular grid may not make the plug-in emissions worse, but clearly electric cars are challenged in those states like North Dakota (the very worst) with 90-plus-percent coal.

On the other hand, California, which will buy more plug-ins than the next five states combined, has a grid that's somewhat cleaner than the U.S. average.

How Green Is My Plug-In, illustration by Holly Lindem

How Green Is My Plug-In, illustration by Holly Lindem

Enlarge Photo

So how green your plug-in car is will vary considerably depending on where you plug it in.

Your mileage may vary

Second, as a follow-on to the points above, how green your plug-in actually is depends not only on what grid you use, but what your comparison car is.

Jalopnik hedged somewhat in its piece by saying, "If you live somewhere with oil or coal-fired power plants, then having an electric car is actually far worse for the environment than a comparable gas or diesel car. This includes many areas of the U.S."

That's largely true, for some areas, if your comparison car is a 2012 Toyota Prius hybrid that gets a combined EPA gas mileage rating of 50 mpg.

It's not nearly as true if you're comparing to a more average U.S. vehicle, which gets 20 to 25 mpg.

Follow Us

Comments (39)
  1. Nice piece and great to have GCR discussion emissions.

    It is also worth noting (but complicates the discussion) that emissions does not equal CO2 as implied in the article. There are many other emissions, CO, NOx, particulate, hydrocarbons, etc, that come out of an ICE that do not come out of an EV.

    Funny how times change. Used to be these other things were emissions, now people think of CO2

  2. Like I've said before electricity is what the automotive industry will use to make zero emission green cars. What the electric companies will ultimately do to go green is a separate issue, it's a related issue but it has been an issue for a while well before the rebirth of the electric car. What bothers me is people only seem to care about power plant emissions when they want to discredit electric cars. The truth is a vast majority of people don't take the time to care where the electricity comes from, it would be like caring about where your trash goes when it magically disappears from the curb.

  3. People also tend to "forget" that electricity is what the oil industry uses to refine gasoline and pump it into your car. Any well-to-wheel analysis that doesn't include this MAY have a hidden agenda.

  4. "in places like Europe where electricity is generated from a wide variety of sources, including renewable energy, they do represent a "10% to 24% decrease in global warming potential (GWP) relative to conventional diesel or gasoline vehicles assuming lifetimes of 150,000 km."

    Keep your EV for over 100k miles and you are cleaner. That is the statement from that study and article...

    Nuff said there.

  5. The study basically indicates the importantance of EVs in saving emission is by keeping the EV running as long as possible. When its life is short, then its impact in emission is actually worse than hybrid/ICE cars. But when its lifetime is approaching 100K miles, then its saving in emission is significant.

    Volt has 100K miles battery warranty!

  6. "In the use phase we tracked electricity and fuel consumption, together with their full supply chains. Use phase energy requirements are based on the performance of the Mercedes A-series ICEV and the Nissan Leaf EV, vehicles of comparable size, mass, and power"

    Problem #1.

  7. Most people should also read the study themselves, especially on the "sensitivity" part of it. The charts shows the variability of the fuel production are much tighter than the variability of the electricity generation.

    So,the study made a lot of assumption.

    Its basic conclusion is that in the worst case, EV can be worse than the "average" good ICE. But in the best case, EV can be way better than the "BEST" ICE. To judge how beneficial EVs are, you would have to look at all the data and it is more than just MPG. That is a fair statement.

    But b/c EVs allow you to "offset" your use phase by using a much cleaner source of energy such as solar, you, the owner can decide how clean the car is where you can NOT do the same in ICE cars.

  8. Oil refineries are the largest commercial user of electricity with the exception of agriculture in California, so burning gasoline actually more than doubles the emission factor if fossil fuels/coal are used for electric generation in refining oil and burnt again as gasoline for the fossil fuel engine. That is not the same standard as a plug in electric vehicle.

  9. ^^ You nailed it.

    The energy lost refining one gallon of gas in the US is about 6 kW*h overall (from various sources, not just the grid).

    So there you have it, just the energy spent refining the gas used by your average non-hybrid is all an EV would need to go the same distance.

  10. You are correct when you said they use increased efficiency numbers for european cars. From their article they have:
    68.5 mL/km = 34.5 mi/gal for gas cars
    53.5 mL/km = 43.5 mi/gal for diesels and,
    .623 MJ/km = .279 Kwh/mile for electrics(LEAF).
    It should be noted that the EPA rated the leaf at .320 Kwh/mile. The difference is the Euro cycle because they got the Leaf number from Nissan. (173 Wh/Km)

    On a side note, doing some quick and dirty calcs. Running an electric car off of the US grid with NatGas Generation runs equivalent to about a 50mpg car. I think, please correct me if I'm wrong.
    (29.3 kWh/gal * 60% Eff * 93% Grid Eff * 3 miles/kWh(Leaf)=49MPG

  11. EPA uses 33.7KWh/gallon.

    so, your math would be 33.7x0.6x0.93*3 = 56.41 MPG.

  12. That is gasoline equivalent of 33.7KWh/gallon.

    I am NOT sure how you compare natural gas in terms of KWh/gallon.

  13. Oh my bad. I forgot to mention that 29.3 kWh number is the gallon gas equivalent of natural gas. With natgas generator efficiency of 60%.

  14. I don't really know of anyplace that generates electricity from gasoline. Small honda generators are probably less than 20% efficient.

  15. That is still pretty good if natural gas can get equivalent of 49mpg. Typically CNG cars get far less than gas cars in terms of MPG.

  16. Yeah, running it off the grid is much more efficient than burning directly in the car. NatGas civic is rated about 27/38. Which is pretty good. Earlier models were even worse than that.

  17. An excellent point - this study is for European consumers, not US consumers. Perspective is key, and your reminder is well taken.

    However, I'd like to point out that buying a used economy car is a far, far better thing for the environment than buying a new electric car...too many times US consumers revert to "new" when used is a very reasonable option.

  18. @Jason: Per M.A. Weiss et al., in the MIT Energy Laboratory's 2000 report, 'On the Road in 2020: A Lifecycle Analysis of New Automotive Technologies,' 75% of a vehicle’s lifetime carbon emissions are from the fuel it burns, and 19% is from the fuel production.

    Extraction of the raw materials that make up the vehicle adds 4%, and only 2% of lifetime carbon is due to manufacturing & assembly.

    While hybrids & may be higher in raw materials & assembly, due to added battery pack & electric machinery, the difference in overall lifetime carbon in manufacturing between electric & gasoline cars is negligible.

    Study: http://web.mit.edu/sloan-auto-lab/research/beforeh2/files/weiss_otr2020.pdf

  19. @Jason: In other words, buying an electric car and charging it in a state with a low-carbon grid will more than offset the incremental carbon emissions of its manufacture. Your total carbon will be lower than if you bought that used economy car.

  20. I agree. But by extending your logic, wouldn't buying a "slightly" used EV is even better? Of course, that is assuming the battery don't degrade significantly.

  21. In areas where there is a large percentage of coal base load power, TIME of charging is very important. This is much more complex than saying a region with coal=more CO2.

    Coal plants (1G MW and larger) do not completely shut down during off-peak. In areas with a large percentage coal power end up producing excess energy (NOT ELECTRICITY!) and their capacity factor fall. In areas with a lower coal percentage, capacity factor is above 90 percent meaning plants running at full capacity 24/7.
    Its ideal for large coal plants to run 24/7 because of: reliability (cost), pollution, efficiency.

  22. 1G MW hmm.. lol
    meant 1GW

  23. They don't shut down at night for a reason. They take a long time to get back up. This is why they are used as base generation because it takes a lot of time to ramp up or down the power output. Same with hydro or nuclear. So they would rather take the efficiency hit and reduce output, or keep generating at peak output, rather than shut off completely. The longer they stay on, the more money they make.

  24. For US west coast states, where the majority of EVs are registered, electricity generated from coal is very low: CA 1%, OR 6%, WA 4%

    "In 2008, about 48 percent of the U.S. electricity came from coal. In August (2012), that total had slipped to 38 percent, according to the Energy Information Administration."

    Very few electric driven vehicles are registered in states where electricity generated from coal is >40%.

    btw: Electric power production in Norway (location of study) is >95% from hydro & wind.

  25. And you can always "improve" that number by installing solar where you can't do anything to "clean up" your fuel by filling it with gasoline...

  26. Looking at the solar powered house above, when will there be a study showing how much of the grid is supplemented by EV drivers installing alternative power production like solar panels? My guess is the small percentage of EV's overall, combined with the growing population of solar, heat pump, and geothermal users, it would make a big difference for effective emissions output.

  27. I had a look at the jalopnik website. and while it was pig headed which I hate, it mostly talked about emissions to create the car and how long it would take to offset the initial handicap.
    where as this article speaks of well to wheel comparisons.
    just and observation.

  28. I have had many discussions about this, especially in Germany. When you look at CO2 emissions, ev's are today better than ICE. You just have to look at well to wheel in both cases (what nobody does) and you have to base yourself on comparable consumption/ emission-standards.
    If you look at all the emissions related to the production, use and recycling of a car, the batteries are still a problem.
    To be honest....

  29. BTW - the NEDC is used in Europe to determine range.
    The standard for consumption is based on that but includes all the charging losses at the lowest charging power.
    The smart f.e. can be charged at 400V/32A, but the lowest possible charging in Europe is at 230V/8A. That makes for long charging and more losses. Thus, while actual driving consumtion is at 13kW/100km, this goes up to 15,1 in accordance to the standard.
    Generally, we use the average national CO2-emission for 1 kWh. There are huge differences between and in the countries.

  30. Always shameless promotion on my end, but below is a link to our Clean Cities Vehicle Cost Calculator. The tool provides consumers with easy to digest information on total cost of ownership and emissions (zip code based electric generation). http://www.afdc.energy.gov/calc/

  31. First off great piece John as usual.
    I have a question.
    For those like me that use solar panels on there house to offset the pollution. In most states the sun does not shine when I would be charging my plug-in (at night). Does pushing energy into the grid during the day and pulling it back out at night count 100% as renewable charging and no polution?

  32. Absolutely - during the day when demand is high your solar panels are powering several homes around you, and in effect are making the neighborhood disappear from the viewpoint of the power plant. Then at night, when there's ample excess capacity in the system, you aren't taxing the system at all by charging. (and the homes around you were fueled by the sun instead of coal for the day)

  33. Just wondering how they are calculating the "pollution" created on manufacturing an EV compared to manufacturing an ICE vehicle? Is this something that would improve with mass production? Is making a battery or electric motor that much more energy intensive than an ICE?

  34. John,
    Perhaps you should study the possibility that most plug-in car owners will plug in after midnight to take advantage of very low rates, and actually use electricity that would otherwise be generated but not used.
    You'll recall that during the brief life of the GM EV car, PS&G offered a $.056 rate per KWh for SO. Cal. EV owners. Nor would it be rocket science to equip plug in owners with reverse meters, allowing them to dump unused juice back into the grid,with time of day credits that actually result in driving at a profit! Solar homes are already doing the equivalent (much to the consternation of some narrow minded utilities). In any event, the claim that plug in electricity will polute more than internal combustion is simply a canard

  35. the Norwegian study is nothing but crap, look at this


  36. Thank you for posting that link. I sometimes worry that I am too cynical about "studies" like this one. Clearly I was not nearly cynical enough.

  37. Union of Concerned Scientists has looked at the emissions of electric cars at different states, where electricity comes from different sources. The bottom line is, even in those states with most of the electricity produced by coal, EVs are at least as good as hybrids. In states with portions of the electricity coming from renewable sources, the easily surpass the best hybrids. A copy of the report can be found at http://www.ucsusa.org/assets/documents/clean_vehicles/electric-car-global-warming-emissions-report.pdf.

  38. Data regarding EV owners in California using solar (among other things) can be found from a recently conducted survey "California Plug-in Electric Vehicle Owner Survey". Currently 39% of new EV owners have already installed solar on their home.


  39. If they are adding the carbon overhead for electricity - are they also adding it for gasoline? Because gasoline doesn't appear out of thin air. It may actually take more electricity to run a gasoline car than an EV - so the "long tailpipe" argument essentially goes away.

    The best estimate I have seen is that it takes ~7.5kWh to make a gallon of gasoline, and it also takes a fair amount of natural gas, as well. So the overhead carbon for both of those have to be added to the total.


Commenting is closed for old articles.

Get FREE Dealer Quotes

From dealers near you

Find Green Cars


© 2015 Green Car Reports. All Rights Reserved. Green Car Reports is published by High Gear Media. Send us feedback. Stock photography by izmo, Inc.