Published on March 25th, 2015 | by James Ayre


Hidden Benefits Of Electric Cars — Even More “Environmentally Friendly” Than Previously Thought

March 25th, 2015 by  

In addition to the most obvious benefits of electric vehicle (EV) use — a diminished carbon footprint, less air pollution, etc — there are many other, more subtle, benefits as well. New research from Michigan State University recently uncovered some of these — to be precise, the research uncovered two previously “hidden” but notable benefits.

Of these, the most notable is the fact that EVs emit considerably less heat — a bit obvious I suppose, but most certainly an important finding regardless. What this means, is that the urban heat island effect can be reduced a great deal by the large-scale adoption of EVs (and phasing out of heat-spewing, gas-powered vehicles).

Nissan LEAF


Considering how hot some cities get during the summer (and how much hotter they will be getting in the future “thanks” to global warming), the application of this finding could go a long ways towards improving livability (as well as reducing cooling bills and energy use). Of course, getting everyone to give up gas-powered vehicles and switch to electrics is easier said than done — for now, anyways.

“It’s easy not to see the big picture on issues like electric cars and global warming, but when we look with a holistic approach, we find these unexpected connections,” stated study co-author Jianguo Liu, the holder of the Rachel Carson Chair in Sustainability at Michigan State University, and the director of the Center for Systems Integration and Sustainability. “Heat waves kill, and in terms of climate change, even one degree can make a difference.”

A recent press release provides more:

The research was led by Professor Canbing Li of Hunan University in Changsha, China, who was a visiting scholar. Conventional vehicles and air conditioners are the two biggest contributors to the heat island intensity — the difference between urban temperatures and the cooler temperatures of rural areas. In that arena, electric vehicles are cooler — giving off only about 20% of the heat a gas vehicle emits.

The researchers used Beijing in summer of 2012 to calculate that switching vehicles from gas to electricity could reduce the heat island intensity by nearly 1 degree Celsius. That would have saved Beijing 14.4 million kilowatt hours and slashed carbon dioxide emissions by 11,779 tons per day, according to the paper “Hidden Benefits of Electric Vehicles for Addressing Climate Change.”

A note to make here — owing to uncertainty of the exact effects of aerosol pollution on heat island intensity, this potential factor wasn’t addressed in the research.

The new findings were recently published in the journal Scientific Reports.

Image Credit: Nissan

Tags: , , , ,

About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • DWilson

    EVs are also quieter, sometime in the future, the drop in noise pollution may cause property values to rise near highways and other loud corridors.

  • Coley

    And how much less energy is used in the production of EVs? No engine or gearbox and associated ancillaries, starter, radiator etc.

    • Martin

      Yes all of that is called life cycle cost of a product.

    • Larmion

      But a huge battery pack with a large embodied energy to compensate.

      Either way, it doesn’t really matter. Cars, no matter their mode of propulsion, have an insignificant embodied energy relative to their total lifetime energy use. Typically, 90%-ish of lifetime energy use comes from fuel/electricity use and the remainder from making the vehicle itself.

      On an interesting side note, that makes them virtually unique among things a typical household owns (refrigerators are another exemption). Computers, televisions and most other consumer electronics tend to have a very high share of embodied energy, so you should keep using them as long as possible even if new models are more efficient.

      • Kiwiiano

        There’s also the way we use cars. I was driving the 320km (200 miles) to visit my daughter, cruising just below the NZ speed limit of 100km/h and calculated that I could make the journey a LOT more efficiently if it was feasible to travel at a maximum of 50km/h. Sure it would take twice as long, but I effectively write the day off to the journey anyway. Humanity managed for the last 100,000 years with the maximum speed of travel being a galloping horse at 40-50km/h.
        And don’t get me started on the size & weight of cars…..

        • Bob_Wallace

          With self-driving cars people might be more willing to tolerate slower driving speeds. If they could do something other than operate the car then an extra 10% to 15% spent on the road might not be so objectionable.

          I’d be happy to go slower on long trips if I could look at the scenery rather than watch to see if another driver is going to do the stupid. Or take a nap when the scenery is boring.

        • Larmion

          Isn’t the optimum efficiency for a typical ICE car around 70km/h rather than 50?

          Either way, you’re absolutely right. Slower speeds would increase efficiency for your own vehicle.

          There is, however, something you have to consider (at least here in densily populated Europe, it might be different in NZ): if you drive slower than the average flow of traffic, you will cause other drivers to decelerate (to avoid rear-ending you) and then to accelerate (to overtake you).

          The result is a situation that is likely less efficient at a system level and certainly less safe. Traffic is at its most efficient when all vehicles travel at a constant speed. Adhering rigidly to the local speed limit is the best way to do that.

          • Kiwiiano

            You’re dead right, Larmion, hence my “if it was feasible”. It would be dodgy trying to drive on NZ’s narrow often winding & hilly roads at much below the legal maximum. Even at the maximum you get a lot of vehicles, including bloody big truck & trailer units, overtaking you.
            My other gripe are the passing lanes the National Roads people have spent zillions building but forgot they needed to set a maximum speed for the slow lane. Consequently we repeatedly get some nitwit dawdling along until he gets to the next 1km passing section then promptly accelerates up to and above the maximum, forcing anyone hoping to overtake into “lose your licence” territory!! resuming his dawdle once he’s back on the normal road. %&$#@*^##!!!

  • JamesWimberley

    Another benefit is less noise. This applies particularly when electric traction replaces big diesels, as with buses.

    • Larmion

      But only at lower speeds. At high speeds, noise from the tires drowns out engine noise anyway, so EV’s no longer win out (they might even lose due to higher weight and thus higher friction).

      That said, noise tends to be less of an issue in places where you can drive at high speed than in the stop-and-go traffic of a city center.

      • jeffhre

        Adoption of EV’s is also spurring work on lower noise rated tires. Which some automakers have been providing as standard equipment.

  • Martin

    Do people forget about the best benefit? Lower ‘fuel’ cost, at 15 cents a kWh, Tesla 60 kw battery, range 300 + km = 20 kWh for 100 km= $ 3.00, at 30 cents kWh =$ 6.00.
    Question: how low would oil and gas prices have to be to compete??
    If the Tesla is to rich for your blood, go with a Leaf, same mileage.

    • I think the assumption is just that’s a widely known benefit. However, how widely known is it really?…

      • Martin

        As I had stated in an other comment, there was a report from a ‘professor’ in Canada, a ‘study’, that in some Canadian provinces is environmentally better to drive an ICE than a EV!!!
        Are people that stupid ???, (can I state that on this site?)

        • Bob_Wallace

          An EV charged on the “US grid” means a bit more particulate pollution in the air than if the miles are driven with an ICEV.

          That’s because our grid is still too dirty. With a couple hundred coal plants closing between now and 2017 we may see a big improvement. The plants closing are the “dirtiest”, the ones which would cost the most to clean up.

          That study may not hold in places like California where coal is getting shoved off the grid.

        • Steve Grinwis

          Hi Martin,

          You heard correctly. The problem is that Alberta has an almost entirely coal based grid, and it’s CO2 intensity is insanely high. Significantly worse than the average U.S. grid figures.

          If anyone has a reasonable challenge to this article, I’d love to hear it, but it seems sound. Coal is nasty stuff.


          • Martin

            Yes but even in Alberta, I used to live there, it is better for the environment to drive electric.

            I just explained that to somebody tonight, the same way I did on the post earlier and they get it.

          • Steve Grinwis

            I can’t seem to find this other comment. Can you link to it? or repost it?

    • slarmas

      some people can’t afford two cars. My diesel is 48% efficient and can go 700 miles at 70mph. It costs about 45 dollars to fill up and I can go again in 5 minutes of refueling time (14.5 gallons). I can also refuel 10,000 times without damaging my fuel tank and losing range. That said I would love an electric car with 800 to 1000 miles range as that is what I drive on a road trip (2 times per year 2400 miles each way. A tesla would take 22 stops at 4 hours each, or 87 hours of charging on this trip. VS 7 stops at 5 minutes each for a total of 35 minutes of refueling time. Not going to spend 1.458 days of my trip waiting for a battery charge.Not to mention as of this writing the tesla would require a 7500 mile trip (3000 going the wrong direction) to stay near superchargers, thus killing any benefit the car has.

  • Kiwiiano

    I think more emphasis should be placed on the extra-ordinary inefficiency of ICE. They usually only convert 30% of chemical energy of the petrol/diesel into movement, most of the rest of the fuel is wasted via the radiator/brakes etc. You wouldn’t be allowed to sell a refrigerator, lightbulb or woodburner that appallingly bad!! Certainly not in NZ.

    • Larmion

      Did NZ ban all light sources then?

      A typical TL tube converts only 15% of electricity used into light. LED’s do a bit better at 25%-ish for a good one. The theoretical efficiency limit for a phosphor led (the kind we use today) is around 40%.

      • Kiwiiano

        Whoops! Looks like I’m guilty of comparing apples with melons then. The percentages I was recalling were of course comparing LEDs, CFLs etc with incandescents. Nothing absolute.
        Begs the question “how do you calculate the ‘efficiency’ of a refrigerator in absolute terms?” You can compare model A with B, it uses less electricity under the same conditions but as a standalone product???
        Or a car with a light bulb? The useful results are too different…..???

        • Larmion

          The efficiency of a refrigirator can be given in absolute terms, if you wanted to.

          A refrigirator is essentially a thermal engine operating in reverse (using energy to move heat rather than moving heat to generate energy). The ideal thermal engine is called the Carnot engine; it’s an idealised engine that can never be built in the real world, but is very important in thermodynamics as it gives you the absolute limit of efficiency.

          The efficiency of a fridge can thus be quantified easily: you calculate the amount of energy an ideal Carnot refrigirator would use in order to bridge a given temperature gap (say a room at 20°C and a fridge interior at 2°C). Then you measure how much electricity the fridge really uses to do the job. Divide both figures and you have the efficiency of the fridge.

          Now that’s assuming you use a reverse heat engine. There are other types of coolers, absorbtion coolers for example (though those are generally only used in large, industrial-scale units). You can extend the same efficiency calculation to extend to those, but that’d go a bit too far for a website comment.

          For your broader point: you can compare a car to a light bulb if you so wished. Efficiency is defined as the percentage of energy a thingy consumes is actually used to achieve its primary function. It doesn’t really matter if that function is lighting, moving stuff or squeezing juice out of jellyfish.

          Of course, that such a comparison is possible doesn’t make it meaningful. Some things are harder than others; you can’t expect a lamp to be as efficient as a heating element.

  • shanti

    How about the hidden benefit of the natural gas and electricity saved in delivering and refining gas? Something like 5 kWh of electricity saved for every gallon of gas not used in your EV. That is 20 miles of range for every gallon saved. Not bad for a hidden benefit.

  • Marion Meads

    That’s great reconsideration about the heat generated by the ICE. However, in very cold places like Alaska, you would need to heat the batteries as well.

    What surprised me is that their calculations seemed to be very off. Only 20% less heat? That doesn’t seem to agree with basic thermodynamics. If an ICE is 25% efficient where the stored energy is converted into motive power to move the car some distance, then the 75% is all lost as heat. From the 25% that was converted to move the car, the same amount of heat will ultimately be generated by either ICE or EV after it moved. So I find it hard to swallow the 20% less heat measurement or argument.

    BTW, what was the other major benefit? You mentioned there were two but only discussed the heat.

    • Oil4AsphaltOnly

      It didn’t say “20% less heat”, it said “20% of the heat”, which would be ~80% reduction.

      • Marion Meads

        It would create more impact and clearly understood if they said 80% less heat, rather than 20% of the heat. The premise was EV produces less heat, so your brain is preconditioned to think in terms of how much less.

        • sault

          Saying that one figure is 20% of another figure is the more mathematically correct way of phrasing things. Gas cars put out X heat while electric cars put out 0.2X as much heat. You know exactly how much they’re talking about without having to think too hard.

          All those 10%, 20% or even 80%-off sales at stores have twisted people to think about things incorrectly. The same way of thinking would lead somebody to say “a cat is 10 times smaller than a human” which doesn’t make any sense, but I hear it all the time. The most logical way to say it is “a cat is 10% of the mass of a human”, but since people are so used to thinking the other way, it is a little confusing.

          • jeffhre

            It’s not confusing, it’s an order of magnitude!

      • I think that 20% is actually too high. An EV uses about 1/3rd (at most) the energy, and it wastes only ~15% of that (and about half of that waste occurs during charging). While an ICE wastes at least 70%, and since it uses 3X as much, that means it produces about 7.1% of the total heat.

        • CR

          Even non-wasted energy ends up as heat in the end.

          • JamesWimberley

            Yes, but the overall efficiency of EVs (something like 85%) plug-to-wheel) is so much higher that their overall heat footprint can be far below the ICE’s. The effect is reinforced by the growing share of lossless renewable generation in electricity. You lose 5% in transmission, whatever the source. It’s a bit of an arbitrary distinction, but the efficiency losses in wind and solar generation are accounted for outside the box, see the LLNL energy flowcharts.

          • CR

            Yes, I only meant that all that matters for heat generation is energy going in, whether that’s electric or chemical. That explains why the number is 20% rather than <10% as Neil Blanchard calculated above.

          • How is that?

            My point is that we cannot just compare the relative efficiencies, without also looking at the quantity of energy used.

          • CR

            Exactly, “the quantity of energy used”, but you cannot subtract the useful work out, since that too becomes heat.

          • The work out doesn’t become heat, I don’t think. That’s the point.

          • CR

            Yes it does. Energy is always conserved, all energy that is put into the car, whether as electricity or chemical energy, is also eventually removed from the car as heat through air resistance (heat to air), friction (heat to ground or the car itself), etc.

            (The only real exception is potential energy: if you drive uphill some of the energy gets stored as potential energy but in that case the car consumes more gas/battery. And if you drive back downhill it averages out.)

          • I stand corrected.

    • n8r0n

      The “two” benefits are related.

      One is that EVs create less waste heat, which keeps cities cooler (a problem in some densely populated, warm cities).

      The second benefit is that because of the first, those cities need to use less electricity to cool themselves. Using electricity is part of what causes the warming in the first place (in addition to car engines that directly give off heat).

      It might make more sense to simply say that gas engine cars produce a double-whammy of warming. They give off waste heat, which in turn causes us to have to use more electricity for cooling, causing more climate change.

      It has to be said that in some (cold) places, waste heat isn’t such a direct problem. However, it’s not a symmetrical issue. Fundamentally, it takes more energy to cool than to heat. Most “machines” produce some heat as a by-product, so air conditioners are always working harder to overcome this bias.

      • Larmion

        The asymmetry holds only if you look at a place where a typical building has both AC and heating. In Western Europe, among other places, very few buildings have AC. That means your point no longer holds.

        That said, heating a city by sending waste heat into open air is quite possibly the least efficient way possible to do it.

Back to Top ↑