By on June 12, 2012

Is the US EPA fudging the way it calculates miles per gallon equivalent ratings for electric and hybrid cars, making EVs appear to be more energy efficient than they really are, increasing their consumer appeal? That’s what Lindsay Leveen, author of Hydrogen – Hope or Hype? A Primer on Energy and Sustainability, says.

The U.S. Environmental Protection Agency calculates MPG ratings based on energy at point of delivery. That means that it ignores the energy costs of drilling, pumping, refining and transporting the gasoline to the corner gas station. When calculating miles per gallon equivalent (MPGe) ratings used to evaluate fuel costs for electric vehicles and hybrids, the EPA also ignores the energy costs of producing and transmitting electricity as well as the energy costs of transforming transmission line voltage to 110/220 VAC and then losses in converting to the Direct Current needed to charge batteries. The EPA also assumes that EV batteries have a charge/discharge efficiency of 100%. Essentially the EPA is treating EVs as though electricity is 100% efficient until it gets to the vehicles’ motors. You could say it does the same for gasoline, not looking at the total energy costs of getting that fuel to market. The agency then mileage tests EVs, dividing electricity consumed by an energy conversion factor of 33.7 kilowatt hours per gallon of gasoline to arrive at MPGe ratings.

So what’s the problem? As long as the EPA is evaluating energy costs at the point of delivery, it’s comparing apples to apples, right? Well, it seems as though some apples take more energy to plant, grow and get to the fruit market than other apples. It’s true that there are extraction, processing and transportation energy costs for all fuels, including the coal, natural gas and uranium used to generate electricity as well as for gasoline. Drilling, pumping, and refining crude oil plus trucking and dispensing gasoline consumes the equivalent of about 10% of the energy in the crude oil.

That 10% energy cost is comparable to the 90% efficiency of electrical transmission lines and local distribution systems, or the 90% efficiency of AC/DC conversion and battery charge/discharge cycles. Those 90% efficiencies, though, if I remember my math terms correctly, are associative – together they yield 81% efficiency, not 90%. Of course, with gasoline, unlike electrical generation, that 10% energy cost is all that’s involved.

You may use some energy getting petroleum out of the ground and then turning it into a useful fuel, but electricity generation that isn’t hydro or geothermal necessarily involves consuming fuel, either fossil or nuclear. Most of America’s energy comes from coal fired power plants. In the near term, what won’t get generated from coal will probably be generated from natural gas (owing to the ongoing boom in gas discoveries and production), not wind and solar power (which have their own energy costs).

Essentially, to run an electric vehicle you’re converting chemical or nuclear energy into heat into electricity. As we know from internal combustion engines, turning chemical energy into heat into power involves waste heat. As Leveen seems to enjoy saying, you cannot avoid the Second Law of Thermodynamics. Entropy exists. Average energy efficiency of electrical power plants is about 42.5%. Multiplying all the efficiencies in getting electricity generated and charged into your car’s battery pack and you come up with 34.4%.

That means that the EV version of the Honda Fit’s EPA rating of 118 MPGe, multiplied by electricity’s inefficiencies, would actually work out to 40.6 MPG. A conventional petrol fired Fit has a combined EPA rating of 35 MPG. Taking that 10% energy cost of production and distribution of gasoline into consideration yields 31.5 MPG. While that still puts the EV Fit as 29% more fuel-efficient than the gasoline version, that’s not nearly as impressive as triple digit MPGe figures. If you’re running a government agency that wants to encourage the sale of electric cars, using the larger figures might make sense but then political science and real science, as Leveen points out, aren’t the same thing.

Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can dig deeper at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS

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54 Comments on “Is the EPA Fudging EV MPGe Figures?...”

  • avatar

    Well, what we really want to know is how much it costs to run each vehicle.

    According to a web forum post which looks pretty well sorted, the Leaf gets about 3.3 miles per kwh.

    If a kWh costs $0.12 then this means each mile costs $0.036.

    The Nissan Versa gets about 30mpg.

    Gas is looking like about $3.50 a gallon now. So it costs about $0.1166 per mile.

    So it costs about 3.19 times more to run a Leaf as a gas engine with a comparable car.

    Curiously enough, this means the 98mpg equivalent Leaf is about right. 30 mpg x 3.19 is 95.70 mpg. If you consider the calculations were probably made based on somewhat higher prices, this is very, very close.

    Not bad, government!


    • 0 avatar

      “According to a web forum post which looks pretty well sorted, the Leaf gets about 3.3 miles per kwh.

      If a kWh costs $0.12 then this means each mile costs $0.036.

      The Nissan Versa gets about 30mpg.

      Gas is looking like about $3.50 a gallon now. So it costs about $0.1166 per mile.”

      Correction is in order:
      Leaf cost per mile is lower, not the other way around.

      Also, I’m not sure that the $0.12 charge per KWH includes all taxes, delivery fees and other stuff that seems to be tagged to my electric bill. If these extra charges are not included, then of course the cost to run electric vehicle will be even greater.

      All this math is for nothing though, as most people were pre-conditioned long time ago to asociate elcetric car with saving money and the environment. I’m sure Chinese people living near the rare earth mines totally get the same notion…

      • 0 avatar

        “Also, I’m not sure that the $0.12 charge per KWH includes all taxes, delivery fees and other stuff that seems to be tagged to my electric bill.”

        It’s easy enough to calculate.

        1. Look at your utility bill and see what your cost per kWh is, all taxes and fees included.
        2. Calculate your cost per mile given the Leaf is rated 34 kWh/100 miles.

        Bonus: Consider how YOUR driving routine will differ from the EPA combined cycle test. The EPA sticker is deficient in helping consumers to estimate their particular consumption.

    • 0 avatar
      DC Bruce

      I think you’re on the right track and agree with you that the only relevant question is what the consumer pays to fuel the vehicle. Presumably, all of the back-end costs of both gasoline and electricity are reflected in the price the consumer pays. Where the government measure breaks down is in the assumption of zero loss between the energy used by the electric motor and the energy paid for by the electric car’s owner. While this is a correct assumption for a gasoline or diesel-powered car, it is not correct for an electric car. There are charging losses and discharge losses from the battery that the consumer has to pay for. Or, put differently, the consumer has to purchase more than 20 kwH of electricity to deliver 20 kwH to the car’s motor. I have no idea how significant these losses are, but they are present. . . and the EV driver pays for them.

      • 0 avatar

        @DC Bruce: “I think you’re on the right track and agree with you that the only relevant question is what the consumer pays to fuel the vehicle.”

        I wouldn’t go as far as to say that it’s the only relevant question, but it is the question that people will expect this kind of product labeling to answer.

        Since everyone calculates the gasoline efficiency from the point the gasoline enters the vehicle, so the MPGe calculation should use the same standard.

        I agree with your conclusion, but I disagree with your dismissal of the peripheral issues as “irrelevant”.

    • 0 avatar

      Too bad you pay for what comes out of the wall, even at that point charging the battery isn’t 100% efficient, so you’re not just paying for the energy used by the EV.

      Come on people…

      Edit, DCBruce is on the right track. I would even go as far as to suspect there are losses in the motor and electronics as well, not unlike a gasoline engine that loses energy to heat… Granted the losses will be nowhere as drastic in a single step with electric.

  • avatar

    “Most of America’s energy comes from coal fired power plants. ”

    Coal is only about 40% of the US power sources and that number is falling.

    • 0 avatar

      According to a consortium of environmental groups, the figure is 57%. I think we can agree that a large fraction of our electricity comes from coal.

      “The nation’s fleet of over 100 coal plants is responsible for 57 percent of the electricity generated in the U.S., more than any other single electricity fuel source.”

      The US Energy Information Administration at their web site says “coal is used to generate about half of the electricity consumed in the United States. Coal is the largest domestically-produced source of energy.”

      • 0 avatar

        Those are old numbers. Like from 2000. Tagbert is correct.

      • 0 avatar

        Coal is indeed the largest single input into the US electrical grid, though it’s not quite as large as powerscorecard (PSC) states. It’s possible the 57% is an old number, though even a decade ago we were at 50-51% from coal. Here’s a quote from the EIA page PSC links to at the bottom of their report.

        “In 2010, 45% of the Country’s nearly 4 trillion kilowatthours of electricity used coal as its source of energy.”

        In northern AL we get our power from TVA. TVA gets 58.8% of its power from coal (per EPA 2009 eGRID) .. so we’re substantially more polluting (CO2) than the national average.

      • 0 avatar

        Natural gas just surpassed coal this year.. so it keeps changing.

        In any case its all domestically produced fuel (electricity) and no money gets sent to Saudi Arabia or the Canadians.. all this money is spent locally and it stimulates the economy to a greater degree than imported oil.

    • 0 avatar

      According to the EIA, coal provided 44.8% of the electricity generated in the US during 2010. The trend was declining as compared to the previous decade, but somewhat higher than it was in 2009.

      • 0 avatar

        The consensus from the analyses I’ve read lately seems to be that driving an EV on coal-generated power plant is roughly as clean (both in terms of pollution and CO2) as driving a Prius.

        In places where the electric generation mix is closer to the national average, driving the EV is twice as good as driving a Prius.

        Of course, an EVs limitations mean that they’re not suitable for all drivers and all roles, but they will work wonderfully for some people. I commute short distances, and live in the Midwest where my nuclear-heavy utility was actually lobbying for a carbon tax because it would screw their competition. Leasing a LEAF (and parking my the Escape or the Prius for 300 days a year) would might be a win for me. There are a lot of people for whom this wouldn’t work, though, and that’s OK — they can keep paying through the nose at pump. :-)

      • 0 avatar

        Here’s are links to one of the analyses I was referring to:
        (Both are written by the same author.)

        I forgot to include the links in my previous post.

  • avatar

    The entire concept of “MPG Equivalent” is utter BS. It’s completely arbitrary and just being used as a [another] phony incentive to guide the hapless sheep to the rainbow-filled unicorn-powered big-government-controlled promised land.

    • 0 avatar

      It’s a flawed metric, but it’s at least well-defined.

      What metric would you use to compare electric energy consumption vs gas energy consumption?

      MPG as we use it is based on the point of supply – eg we fill up 10 gallons, and drive 300 miles, we say 30 mpg. We can quickly calculate costs by $3.50/gal (our cost as a consumer) / 30 mpg = $0.117/mile.

      MPGe or kWh/100 miles are also based on the point of supply – eg we put 35 kWh into a Nissan Leaf and drive 100 miles. We again can quickly calculate costs by $0.10/kWh (our cost as a consumer) * 35 kWh/100 miles = $0.035/mile.

    • 0 avatar

      Arbitrary? Any unit you define is arbitrary–kWh, BTU, gallon equivalent, etc. But the amazing thing about science is that the results are valid regardless which you use.

      Efficiency is output/input. For a car, the output is how far you drive, and the input is the fuel you put in. If you fill your car with only electricity, it would make sense to measure it with kWh since that’s how you are billed, but unfortunately we have multi-fuel cars that use both electricity and gas. Do you think using different units for the different fuels will help consumers? That’s like giving speed in mph and distances between towns in km.

      No matter how flawed it is, mpge is the simplest solution. People already understand it, and it is already being used for the gas portion, so why do something even more confusing?

      As to your belief about the intent and purpose of mpge, all I can say is that I hope the view from under that foil hat is pleasant.

      • 0 avatar

        Wait. If you believe in Science, you would use Joules, since that’s the only acceptable measurement for energy in science. Joules are not an arbitrary unit, we use them after centuries of experience with various unitary systems, and represent the most systematic and scientific way of thinking about energy.

        kWh are equivalent to Joules (to a constant factor), so they could be defended as scientific.

        But there is not a scientific basis for MPGe. It’s a marketing number, based on the flawed assumption that the energy content of a gallon of gasoline is somehow important. Given the complexities of alternative fuel production, distribution, and fueling, MPGe falls on its face. It only makes sense if you share the same assumptions as the people who created it. If you care about something else, like gCO2/km, or $/km, etc., MPGe is completely misleading.

        That’s why we have Joules. As a scientific unit, when we use Joules, we all agree on what we’re measuring, and what we’re not measuring. MPGe conflates many different issues, which leads to articles like this – the perfect example of why MPGe is an antiscientific concept.

        Please don’t invoke science to defend MPGe. It’s just marketing.

      • 0 avatar

        “If you believe in Science, you would use Joules”

        If it makes you happy, MPGe can also be expressed in terms of joules.

        “If you care about something else, like gCO2/km, or $/km, etc., MPGe is completely misleading.”

        If you care about something else, then you measure that something else in its own terms.

        MPGe was meant to provide the consumer with a familiar yardstick. Since consumers are accustomed to buying gasoline in volume measures, MPGe basically does the same thing.

        If you don’t like it or if you want different information, then the answer is simple — go calculate whatever else it is that you want to calculate. No one is going to stop you from gathering other data.

        You wouldn’t measure someone’s height using kilos or their height using gallons; humans should have the flexibility to make the appropriate adjustments.

    • 0 avatar


      The part that’s arbitrary is that both electricity and gasoline-made-motive-power are the result of fossil fuels being fed through the Carnot cycle. But, for gasoline, the Carnot cycle happens in the car, and for electricity it happens elsewhere. The arbitrary part is that we count the Carnot cycle losses for gasoline, and we don’t count it for electricity. Any physicist will tell you this is arbitrary and unfair.

      But, we charge end-users for gasoline before the Carnot cycle losses, and we charge end-users for electricity *AFTER* the Carnot cycle losses. Any accountant will tell you that this is the *RIGHT* way to deal with costs, because that’s what you pay.

      So, who are you with? The physicists, or the accountants? My reflex is to side with the physicists, but most people are more concerned about costs — so it’s appropriate to label the vehicle with MPG and MPGe numbers that can be used to calculate the vehicle’s operating costs.

      • 0 avatar

        “But, we charge end-users for gasoline before the Carnot cycle losses, and we charge end-users for electricity *AFTER* the Carnot cycle losses. Any accountant will tell you that this is the *RIGHT* way to deal with costs, because that’s what you pay.”

        The end-user is paying X for a given unit for gasoline, electricity or whatever. The level of mechanical inefficiency, whatever it happens to be, is implicitly built into the price, as that indirectly impacts demand.

  • avatar

    Judging from all the confusion Bertel ran into trying to research the mpge of various vehicles and finding conflicting numbers everywhere?

    I don’t think the EPA would KNOW it was fudging numbers even if it WAS.

    • 0 avatar

      “Judging from all the confusion Bertel ran into trying to research the mpge of various vehicles and finding conflicting numbers everywhere?”

      There was no conflict. Mr. Schmitt didn’t understand what he was reading. I provided an explanation on that thread.

      (To be fair, it was confusing. But that doesn’t change the fact that he got it wrong.)

  • avatar

    “The EPA also assumes that EV batteries have a charge/discharge efficiency of 100%. Essentially the EPA is treating EVs as though electricity is 100% efficient until it gets to the vehicles’ motors.”

    False. The EPA MPGe ratings and kWh/100 mile ratings are based on energy consumed at the wall. Charging (AC to DC), balancing, and discharging (controller, DC to AC, motor) losses are all included in this figure.

    That’s a pretty basic error to trip up over.

    Transmission losses I’ve read are closer to 95-97%. That may be just losses in the line, various voltage conversions may incur additional losses.

    Total energy efficiency of gas well to pump is around 75%. Not sure what the equivalents are for coal, natural gas, and nuclear fuel .. but they’re certainly not 100% efficient.

    In a location like Hawaii where the grid inputs are nearly 100% fossil fuels (oil), the Leaf is responsible for around 40 mpg in gas consumption. In this case Prius is better.

    In the US in general, we get significant portions of our national energy from hydro, nuclear, and renewables. Counting the consumption of fossil fuels into the grid (coal and natural gas) — which the EPA SHOULD do — the Leaf is probably closer to 80 MPGe.

    As Tagbert points out, coal is falling and renewables are rising. Electric cars are the only cars that get cleaner as they age (catalytic converters are typically rated for 75k or 100k miles, for example).

    • 0 avatar

      “False. The EPA MPGe ratings and kWh/100 mile ratings are based on energy consumed at the wall. Charging (AC to DC), balancing, and discharging (controller, DC to AC, motor) losses are all included in this figure.

      That’s a pretty basic error to trip up over.”

      Yep, pretty much. The whole argument being made by the blog is utter nonsense. This should be obvious, but some folks are gullible enough to believe it.

      One could analogize it to MPG for a car. The standard MPG figure is the number of miles traveled on a gallon of whatever. It does not directly account for the energy that was used to find oil, to turn that oil into fuel, and to transport that fuel to the retailer, nor does it need to.

      There’s no reason for MPGe to be any different. One can debate the relevance of MPGe, but one can’t fault it for its consistency.

    • 0 avatar

      Very sharp analysis.

    • 0 avatar

      “Transmission losses I’ve read are closer to 95-97%.”

      That should be transmission efficiency.

      The EIA claims 7% losses (93% efficiency) in transmission and distribution.

  • avatar

    “Electric cars are the only cars that get cleaner as they age (catalytic converters are typically rated for 75k or 100k miles, for example).”

    Is this really true? These cars are using Lion batteries right? I know the battery capacity in my cell phone and laptop have degraded significantly over time. Has this side effect of use been completely eliminated on auto packs? If not range will degrade along with battery function requiring more frequent charges.

    • 0 avatar

      Yes, the batteries will degrade over time. Nissan estimates 80% original capacity after 7-10 years. While they do use lithium ion batteries, the design priorities are radically different from batteries used in laptops and cellphones (in a similar fashion that the Honda S2000 I4 is radically different from say a 2.4L truck I4).

      Note that (to the best of my knowledge) charging efficiency should roughly stay the same. While you may charge more frequently, your kWh consumed per mile should remain unchanged. More likely you will just continue to charge at work and home, but the charges will be deeper charges over time. When the batteries degrade beyond the point of your comfort level, then you can replace & recycle the old battery pack or sell the car to someone whose range needs are well satisfied.

      Speaking generally, grid energy and emissions are trending towards a cleaner grid. So while the car itself is not getting cleaner, the total impact per mile driven should get cleaner over time.

  • avatar
    B Buckner

    So taking into account the efficiencies of electricity, and assuming your electricity is generated by coal, natural gas or oil as is the case for most of us, your carbon emissions will be much higher with the electric car, which is the whole point of the electric cars after all.

    • 0 avatar

      Huh? How on earth did you come by that conclusion? The article, flawed as it is, as pointed out in the comment above, says that the electric Fit is 29% more fuel efficient than the gasoline Fit. So , to a first order, it emits 29% less greenhouse gas.

    • 0 avatar

      National grid generation, 2010, of electricity is 4,125,060,000 MWh.
      National grid generation, 2010, of CO2 is 2,388,662,000 metric tons.

      This averages out to 579.1 g CO2 /kWh.

      Per the EPA, the average heat content per gallon of gasoline is 0.125 mmbtu/gallon and the average emissions per heat content of gasoline is 71.35 kg CO2/mmbtu.

      This works out to 8919 g CO2/gallon.

      Combined cycle EPA, EV:
      2011 Nissan Leaf, 34 kWh/100 miles => 197 g CO2/mile
      2013 Honda Fit EV, 29 kWh/100 miles => 168 g CO2/mile

      Combined cycle EPA, gas:
      2010 Toyota Prius, 50 mpg => 178 g CO2/mile
      2012 Honda Fit, 30 mpg => 297 g CO2/mile

      Taking the national grid as a whole, the most efficient EV is responsible for slightly less CO2 than the most efficient gas vehicle. If your particular area gets more (or less) of its energy from non-fossil resources, then EVs may be more (or less) efficient than their gas counterparts.

      However, emissions (today) are just one system-level advantage of EVs.
      1. Future emissions decrease as the grid cleans up.
      2. Non-GHG emissions are farther from population centers.
      3. Domestic energy keeps money in the US, keeps us employed. We import 70% of our oil. We import 30% of our oil from countries that are strongly anti-US.
      4. EVs can be completely decoupled from fossil fuels (at significant expense). Conventional ICE needs a biofuel breakthrough to do likewise.

    • 0 avatar

      Note that the energy* required to make a single gallon of gasoline, from the well to the gas station would get you 35 miles of range in a Leaf.

      *that includes electricity, natural gas used to make H2 and bunker oil used for process heat.. processing tar sands bitumen into gasoline is much worse, about 1/3 of the energy is consumed.

  • avatar

    Out of curiosity .. while the question posed in the article title is worthy of consideration, why link to this particular source?

    1. He’s tripping over a basic misunderstanding in what the EPA metric reports (and then making flawed arguments in his blog comments).

    2. His report on hydrogen doesn’t appear to be particularly noteworthy. Amazon reviews are.. well, three of them (posted within the same month) follow the exact same format. A scientific paper in a peer-reviewed journal carries a lot more weight than a self-published Kindle title with limited readership.

    3. Mr. Leveen is particularly vitriolic and displays a heavy political slant in his responses to commenters on his blog. This doesn’t detract from his argument, of course, but gems like “Morons like you”, “As I type my response to your idiotic comment”, “I do not need an idiot like you to agree with me” aren’t particularly endearing. Topics like MPGe are worth discussing on their own merits (as we’ve done here) without dragging a politically charged viewpoint into the fray.

    • 0 avatar

      “displays a heavy political slant…”

      which, conveniently enough, happens to match Mr. Schreiber’s worldview.

      Leveen’s “story” hit the right-wing blog circuit two days ago. TTAC appears to have faithfully regurgitated it today.

      • 0 avatar

        I must have regurgitated it just after I cashed my check from the Koch brothers.

        Coming from someone who never fails to reliably push the collectivist, statist view, the view that government is the solution to all problems, I’ll simply regard your comment as more projection.

      • 0 avatar

        In other words, you got it from Breitbart, but you don’t want to admit it and you’re very defensive about it. Figures.

      • 0 avatar

        “In other words, you got it from Breitbart, but you don’t want to admit it and you’re very defensive about it. Figures.”

        I actually found out about it at Jeff Goldberg’s Protein Wisdom site. It looks like PW got it from Big Government, but I don’t read all of the Big sites or every day. I didn’t know that Big Gov’t had picked up Leveen’s post until you brought up Breitbart and I went back to Jeff’s site and I see now that the writer there had hat tipped Big Gov’t. I hadn’t noticed that link to BG before, because I like going to original sources when I can and there was a link to Leveen’s blog post right at the top of the PW post.

        Not that there’s anything wrong with getting info from a Breitbart site, but like I said, I don’t like relying on secondary and tertiary sources if I can avoid it.

        It’s almost humorous the way statists use Andrew Breitbart as some kind of shibboleth and use his name as a boogeyman (like they do with Koch – and like some on the right do with George Soros – though Soros really is a boogeyman who helped Nazis hunt Jews). Andy Breitbart was was warm and gracious to me and I’ll keep his phone number in my cellphone if only because I know that it will annoy folks who hated and continue to hate him, but mostly because I admire how fearless Andrew was.

        I think it would be too cool if the Breitbart organization had a site called Big Cars to go with Big Government and Big Hollywood. I think the name would be terrific, filled with irony and multiple meanings.

      • 0 avatar

        “I actually found out about it at Jeff Goldberg’s Protein Wisdom site.”

        My apologies. You got it from a different absurd right-wing blog, which cribbed it from Breitbart. That’s an entirely different point from what I was making (cough, cough.)

        Just a thought, but maybe you wouldn’t be a sucker for such hackneyed material if you’d escape from the echo chamber and read more neutral, informed material, instead. I realize that you are desperate to find others online who agree with you, but they don’t do you or your credibility any favors when they mislead you and spin you full of half-truths.

    • 0 avatar

      Since you asked, I posed it as a question because I’m not necessarily endorsing Leveen’s position. I linked to that source, because it’s where I found the info. I haven’t reviewed his hydrogen writings, I simply noted that as a means of identifying Mr. Leveen. I also agree with you about his vitriolic nature.

  • avatar

    Speaking as an engineer myself, I believe Leveen is correct, and the EPA incorrect.

    Heavy crude oil, such as bunker C as used in many thermal power plants to generate electricity outside the US, has a calorific value of 150,000 Btu per US gallon. Gasoline is 114,000 Btu per gallon.

    The cycle efficiency to get electricity from the plant, through the T/D system to the wall plug, then charge the vehicle battery through an inverter and keep it cool while doing so, is about 33% on a good day. So only 49,500 Btu is available from that original gallon of heavy oil within the car battery.

    The Volt uses only 8kWh of its 16kWh capacity to drive the car before the range extender kicks in. That is 8kWh times 3412 Btu/kWh or 27,200 Btu. On that amount, the Volt will go about 30 miles.

    On 49,500 Btu, the Volt will electrically travel 30 x 49,500 / 27200 = 54.6 miles. The gasoline mileage equivalent is 54.6 x 114,000/150000 = 41.5 mpg.

    Various professors of thermodynamics I had years ago in college used to try to beat it into us: Maximum efficiency occurs with only one energy conversion. Hence, it’s better to use raw oil and natural gas in a furnace to heat a home, rather than use electricity with its three conversions to directly heat a resistor. However, electricity is a very high grade of energy, so man invented heat pumps to utilize electricity more efficiently to heat and cool homes by pumping heat from one environment to another, i.e. inside/outside. What we need is an equivalent of a heat pump for electric vehicles. Hmm..

    BTW, if another mechanical engineer can find anything wrong with my figures, I’m all ears. It appears to be the same conclusion Leveen came to.

    • 0 avatar

      I am not a mechanical engineer and your reasoning seems fine. Except that you you detail the heavy crude oil used in some electricity generation plants and use this in your equations. Most electricity does not come from oil. In the UK less than 5% of the countries electricity comes from oil – instead it is renewables, coal and nuclear. The same is, I believe, true for the US and other Western countries (which are the ones who have Volts, Leafs, Prius plug-ins etc). So I don’t fully understand your point, unless coal and nuclear also have similar BTU values

    • 0 avatar

      What is MPGe?

      MPGe, or miles per gallon gasoline equivalent, conveys the energy consumption of a non-gasoline vehicle in terms of how many miles the vehicle could go on an amount of fuel that has the equivalent energy content as a gallon of gasoline. For example, a gallon of gasoline has the energy equivalent of 33.7 kilowatt-hours of electricity. An electric vehicle that uses 33.7 kilowatt-hours to drive 100 miles will use the energy equivalent of one gallon of gasoline and, therefore, would have an MPGe of 100 miles per gallon of gasoline equivalent.

      It’s not measuring what you think that it’s measuring.

      • 0 avatar

        @Pch101: Thanks for giving me the EPA definition. It’s obviously a silly definition. Sure there are 33.7kWh equivalent in a gallon of gas. That’s easy to see – 114,000 Btu divided by 3412 Btu per kWh gives about 33.4kWh.

        The problem is, a gallon of gasoline just sitting there is useless. It has to be put through a machine(s) to make useful work, with a cycle efficiency of about 33% for electricity. My figure stands as the real world efficiency, so I can see what the EPA says, but regard it as highly disingenuous, and not rigorous in any engineering sense.

        Other commenters have quoted studies that show the real equivalence of electric vehicles to average gas ones as a bit better than 1:1. So my quarrel is with the EPA definition.

        @ Mike978: Don’t get hung up on my using heavy oil as the basis of electricity generation. You’ll get the same result from coal ot gas. Each fuel contains so many Btus per pound or gallon or therm that can be burned and released as heat. The problem is, that heat has to be changed to motion or mechanical work. Then we see the inefficiencies of each process. The EPA is rating electric vehicles mileage as if no energy conversion process had to occur. Might as well say that a 25% efficient gasoline vehicle that gets 25mpg is 100 mpg equivalent. The EPA definition is useless, obviously.

        The point is this: if I have a gallon of gas to use to move a vehicle, I can burn it in a small car and get perhaps 40 miles. If I take that same gallon of gas, burn it, generate electricity, transmit it to an electric car, I’ll get about the same distance, not over a hundred miles like the EPA says.

      • 0 avatar

        “The problem is, a gallon of gasoline just sitting there is useless. It has to be put through a machine(s) to make useful work, with a cycle efficiency of about 33% for electricity”

        What MPG and MPGe have in common is that neither is a well-to-wheels measure. The blogger in question asserts that it should be, and he’s wrong to make that claim.

        MPGe, like MPG, measures how far a car can travel with a given quantity of energy. It’s a perfectly logical approach to measuring a vehicle’s energy consumption, even though it is not an efficiency measure, per se.

        MPGe makes it pretty clear that an EV can travel much further with a given amount of energy than can a gasoline car, which would suggest a much higher level of operating efficiency. (This disparity makes sense; the difference amounts to being about a factor of three.) But by implication, MPGe also points to the drawback of electric vehicles — batteries don’t store nearly as much energy as does a tank of gasoline, which limits their usefulness. For EVs to serve the masses, the MPGe is going to have to climb and/or the power storage is going to have become much more useful in the real world (i.e. smaller and lighter.)

  • avatar

    You know, the answer to the question of the OP was answered just a few weeks ago. It looked at source-to-car pollution efficiency of EVs depending on region (and thus electric power source). It was published on this site as well as other car sites. At worst (in CO), EVs are similar to a 35 mpg car. At best, they are near the 100 mpg on the sticker. Granted, that’s for pollution, not energy consumption, but except for a limited amount of green generation, power generation means pollution, so they correlate.

    Another very good indicator is cost. The less something costs, generally the simpler (and more efficient) the process for obtaining it. After all, if it takes a lot of work/energy to extract aluminum or titanium from the ground, you can expect them to cost more than easily extracted metals, like iron. Similarly, if electricity costs less than gasoline for the same amount of energy, you can bet the inefficiencies of the process of getting it are no worse than those for getting gasoline.

  • avatar

    @Pch101: I couldn’t care less what the blogger is saying. I’m not interested in him, nor your ad hominem attack on him. The math is correct.

    An electric car is not three times more efficient than a gas car, sorry. You are describing an almost perpetual motion machine with that argument. All that’s happening is that the energy it’s carrying in the batteries has already been converted to a useful form, electrical energy, with two-thirds of the available original energy already thrown away as heat generating the electricity.

    The gasoline in a gas tank has yet to be converted to heat and work. When it is, two-thirds will be thrown away as heat. The efficiency is therefore about the same. As an engineer would understand, but not apparently, the EPA.

    As you so often admonish others, read and understand what I’ve written.

    • 0 avatar

      “An electric car is not three times more efficient than a gas car, sorry.”

      The European Union would disagree with you: “Electric vehicle ‘tank-to-wheels’ efficiency is a factor of about 3 higher than internal combustion engine vehicles.”

      The Physics Department at UBC would also take issue with you:

      • 0 avatar

        Well, I read those links and they’re poppycock too. They both assume that the electrical energy in the “tank” is the same as the raw energy in the equivalent amount of unburned gasoline. They neglect mentioning how the electricity got in their “tank” in the first place. If you do that, sure it’s three times better, but it’s a rubbish statement.

        I’ll give one more example. I have two half-gallon tanks of gasoline in front of me. I have two cars, one a Cruze, the other a Volt in discharged state. I also have a 10 kW Honda generator, the one with a whole 35% efficiency, that’s my electricity source.

        Step 1. Put 1/2 gallon of gas in Honda generator. Charge Volt until gas runs out.

        Step 2. Put the other 1/2 gallon of gas in the Cruze.

        Step 3. Utilizing two drivers, proceed in convoy together.

        Result: Cruze goes 18 miles before engine dies. Volt’s range extender comes on goe after it goes 18 miles. That’s what my math in the posts above showed. Real world, not an exercise in learning how efficient an electric motor is.

        I had hoped you would use your own logic to analyse the situation. Instead, you go roaring off round the net looking for fatuous links to “prove” I’m wrong. I’m not. What is apparent is that you don’t understand the processes involved, and are resorting to random links to back an argument whose implications you don’t understand. At all. Disappointing – I like your financial reasonings.

      • 0 avatar

        “They neglect mentioning how the electricity got in their “tank” in the first place.”

        I realize that you’re having difficulty with this concept, but when you’re measuring TANK-to-wheels, then you begin with the TANK, and **NOT** with the WELL.

        Well-to-wheels is a different measure. MPG and MPGe are **both** tank-to-wheels measures. They are measuring the same thing — how many miles that a vehicle can travel based upon a given number of BTUs/joules/kwh from the “tank”.

        I noticed that MPG doesn’t get your goat in the same way that MPGe, and that lack of consistency betrays your position. We don’t calculate MPG differently for gasoline made from sweet crude vs. gasoline made from shale, even though the latter requires more energy, and yet you expect something else for electrics.

        As for your claim that we can’t do the math without turning gas into electricity, that also misses the point. But I suppose that you know more than the UBC physics department, and we’re all supposed to cede to your unsourced wisdom, because you say so.

      • 0 avatar

        @wmba You suggest putting a half gallon of gas into an ICE (internal combustion engine) and putting half a gallon of gas into “a 10 kW Honda generator, the one with a whole 35% efficiency” which will be used to charge an EV (electric vehicle). You estimate that both cars would go the same distance.

        Assuming you’re right, it’s still an improvement to use the EV. There are lots of reasons why. For one thing, you’d have the flexibility to get your electricity from a wide variety of sources, like solar, wind, nuclear, coal. If you want to minimize CO2 per kWh, or minimize cost, you have options. With the ICE engine, you’re stuck with gasoline.

        Even if you got your electricity from petroleum, consider this… would it be more efficient to have a single power plant generating enough electricity for 1,000 EVs or 1,000 tiny generators carried around on the backs of the vehicles they power? Which would be more likely to get the proper maintenance and emission controls upgrades?

        Getting back to the original question, what’s the fairest way to compare the efficiency of an ICE to an EV? You could (A) figure it by comparing net CO2, but the conversion would be all over the place depending on what’s your source of electricity. You could (B) figure it by cost, comparing $1 of electricity to $1 of gas, but you’d still have the problem that electricity prices vary widely depending on location. Or you could (C) pick a ratio and stick with it, comparing on joule of electrical energy to one joule of chemical energy. The EPA picked C, but frankly no matter which of the three options you pick, EVs end up getting higher ratings than ICEs.

  • avatar
    Robert Schwartz

    MPGe is an attempt to compare apples to oranges. It is therefore a distortion and it proves nothing.

  • avatar

    “The EPA also assumes that EV batteries have a charge/discharge efficiency of 100%. Essentially the EPA is treating EVs as though electricity is 100% efficient until it gets to the vehicles’ motors.”

    What? NO! The EPA gets the MPGe number from the power being inputted to the charging port in the car. So the EPA doe account for inefficiencies with charging the battery pack and delivering power to the electric motor(s).
    I don’t believe it takes into account the inefficiency of the external charger.
    I can’t believe I saw the quoted text in this article because it isn’t true.

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