Energy Efficiency

Published on August 7th, 2010 | by Susan Kraemer


Internal Combustion Engines Are Still 85% Inefficient

August 7th, 2010 by  

You might be surprised to hear, that after all this time, with so many compelling reasons to make vehicles more energy efficient, that the internal combustion engine still only uses 15% of the energy it receives from gasoline. I sure was.


A century ago, when the internal combustion engine was invented, climate change and peak oil were hardly on the radar. But even today, a century later, with all we know now, a solid 85% of the energy derived from oil is still wasted on the gas car.

According to the EPA, 62% of that loss is right in the drive line.

About 17% is wasted in idling. Braking wastes 5.8%. Friction between wheels, bearings loses 4.2%, air resistance 2.6% and stereo, A/C and power windows use 2.2%.

Electric vehicles will finally re-enter the market this year in the US. EV technology was abandoned quickly a century ago, with just the installation of a few trolley car systems around the nation (that are still running). Legislation in California in the 1990s forced auto companies to revisit the idea, in order to reduce greenhouse gases, and now, despite an initial decade or two of legal action in lieu of innovation by the auto companies, the technology is finally turning up in showrooms.

Electric vehicles are about 90% efficient in their use of electricity, but if you live in a state that is largely coal-powered (Indiana, Wyoming, Kentucky) then the electricity itself is inefficiently produced. Coal-fired power from the utility is typically only 30% efficient.

Solar power on the roof is the best option for powering an electric car if you live in one of the eight states where solar panels are now cheaper than the utility with solar leases or power purchase agreements, with SunRun in California, Arizona, Colorado, New Jersey and Massachusetts, Solar City in Oregon, California and Texas, or Gro Solar in Pennsylvania and California.

Solar may not be that efficient either, but its wasted energy doesn’t cause climate change and there’s no peak sunshine for the next few billion years.

Image: Flikr user Roger Moore

Check out our new 93-page EV report, based on over 2,000 surveys collected from EV drivers in 49 of 50 US states, 26 European countries, and 9 Canadian provinces.

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About the Author

writes at CleanTechnica, CSP-Today and Renewable Energy World.  She has also been published at Wind Energy Update, Solar Plaza, Earthtechling PV-Insider , and GreenProphet, Ecoseed, NRDC OnEarth, MatterNetwork, Celsius, EnergyNow, and Scientific American. As a former serial entrepreneur in product design, Susan brings an innovator's perspective on inventing a carbon-constrained civilization: If necessity is the mother of invention, solving climate change is the mother of all necessities! As a lover of history and sci-fi, she enjoys chronicling the strange future we are creating in these interesting times.    Follow Susan on Twitter @dotcommodity.

  • Paul Borner

    air resistance 2.6% and stereo,??? The greatest amount of energy use in a fast moving vehical is air resistance.
    We have developed a new internal combustion engine. BESS. Look at

  • This is the worst part of all of the exciting updates with renewable energies- most of them dont touch on transportation fuel, Really the biggest thing we can do to cut down on our fuel consumed is to look at our trucks. If we could clean just our the fuel that ships our average food 5,500 miles before it reaches our plates we will be in a MUCH better place. The rest can be step 2

  • Rom

    At least change the title to correctly reflect the loss being to the entire car and not just the engine. You say car, then go on to do the math for the brakes, drive train, AC, etc.. Electric cars will have things like AC and radios. You should leave those out. Also, how they build the electric car affects the amount of waste or efficiency as well. motors at the wheel do not waste on drive train for example.

    I am a big supporter of electric drive cars but I want to be sure the information being put out is accurate so as to not bring unwarranted negative attention.

  • That should be: “62% of that loss is right in the DRIVE TRAIN.”


    Drive train, gas tank — only a matter of details… The real problem is that those of us living in the ‘civilized’ world will soon be facing severe fossil fuel shortages and the end of life as we have known it. Electric cars to solve the problem? Not a chance. The global economy is already imploding — and we haven’t even begun to accelerate down the far side of Peak Fossil Resources yet… so how the heck are the members of ‘civilization’ supposed to afford electric cars? Meanwhile 95% of the global rare earth mineral ores, necessary to build electric cars, is in China — and they have banned the export of such materials in the raw, they will only sell them as finished products… Simple, easy, non-functional answers only make sense to the uninformed. Without sufficient fossil fuels we will be encountering big problems; We grow, ship, store and cook most of our food with oil and natural gas — so clearly we can expect famines on an unprecedented scale, then massive epidemics. Most of the water used in the civilized world is pumped with energy derived from fossil fuels… most of our medicines… plastics… paints… think about it, most of the ‘stuff’ that comprises ‘civilization’ is made from and moved with, fossil fuels. Last but not least, using fossil fuels is causing Catastrophic Climate Changes… which unchecked will cause our EXTINCTION. If we don’t want to die, then we have to change.

    • @Rick Thanks, fixed.

      Good points… we are in serious trouble, all right. More “stuff” – the asphalt for roads to drive on, also made with oil.

  • JTH

    EV only twice as efficient, until you consider generation and transmission losses.

    Now let’s consider the rest:

    Idling – that can be solved, some by traffic control, some by “instant on” controls.

    Also there are variable displacement engines – shut off cylinders when not needed.

    Regenerative braking – which I like with Hybrids

    Drivetrain – maybe EV can be a bit better, if you place motors in hubs (but then you have nasty suspension issues – unsprung weight is bad)

    Rolling resistance – tires – trade off of traction vs rolling resistance, AND proper inflation is major issue – moot

    Air resistance applies to all vehicles – moot

    Stereo, A/C etc also applies to all – moot

    Lets now look at the energy to make the batteries, disposal, carrying excess weight of batteries when partially discharged.

    Conclusion – inconclusive

    [SK: That’s why I think distributed solar is key for charging EVs, no transmission line losses from your roof, DC to AC loses some, but again, any wasted solar energy is not heating up our habitat]

  • NOtis

    Care to explain how 62% is wasted in the gas tank? I’m not doubting the EPA’s number, just annoyed by the ambiguous way it was reported in the article.

    Additionally, you might want to consider citing actual solar efficiencies (instead of just saying that they’re not that efficient); it would definitely dull the sharp twinge of propaganda you have going here. Also consider re-wording your claim that wasted solar energy (sunshine) doesn’t cause climate change. After all, greenhouse gasses don’t cause a greenhouse effect if there’s no solar radiation for them to trap.

    I’m all for EV’s and renewable energy sources. I just don’t like bad reporting.

  • Ben

    Not much longer.

    We R developing a significant efficiency superior engine

  • I have a 4kW PV system and drive an electric truck. When gas was $4 per gallon, it was nice to get “free fuel”.

  • This article needs a lot of work. There are so many problems with it, that I won’t start even though my finders are itching at the keyboard starting with the headline. I will try to be supportive, and assume that you are trying to do a good job. I am always thankful when people are discussing energy issues. If you would like have a discussion to lead to a more accurate understanding of the issues that you bring up please write.


  • We sell financed systems in CA, MA, NJ, and PA. Working with SunRun for financing, we can provide electric rates similar to or LOWER than the utility, while supplying clean, safe, solar power right on your roof!

    Now is the time to install solar, not just to power an EV, but also to power everything else electric in your home. Solar is very reliable, is simple (no batteries), and affordable just about everywhere. In CT, VT, MD, DE, VA, NH, DC, NY, we don’t offer financing (yet), but systems are still very affordable and create inexpensive electricity.

    Jeff Wolfe, CEO, groSolar

  • George

    What a load of crap!

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