Best Answers to the Riddle of 230 MPG

August 17, 2009

Taking its place right next to other great existential riddles—such as “What is the sound of one hand clapping?”—GM’s claim that the Chevy Volt plug-in hybrid will get 230 mpg left journalists bewildered about its meaning.

GM executives said they used a preliminary EPA methodology to determine the MPG of the Volt which uses only electricity for approximately 40 miles, then uses gasoline to recharge batteries until the vehicle can be recharged with more electricity. But the EPA has not finalized its procedure, has not tested the vehicle, and is not claiming responsibility for the 230 mpg figure.

Here are our favorite candidates for the best explanation of a number that defies explanation. We hope it clears up everything.

More Than Infinity

“Under the rational that GM says the EPA applied to the Volt, an ell-electric car such as the upcoming Nissan Leaf or existing Tesla Roadster would have an official rating of ‘infinity miles per gallon.’”
- John O’Dell, Edmunds.com Green Car Advisor

Nuclear-Powered Cars

“If the Volt were powered mostly by a windmill or a nuclear reactor, it would also get great gas mileage, since the fuel would be coming from some other source.”
- Rick Newman, US News and World Report

Back on Gas

“The 230-mpg number, according to GM’s Frank Weber, global vehicle line executive for the Volt, is a measurement of the car’s ‘city-driving cycle.’ If the Volt got out on the highway—where it’s powered largely by gasoline—and traveled 200 miles, the mpg would drop like a stone.”
- Robert Chew, Time

The Point of Diminishing Returns: 51.11 Miles

“The charming dorks at Environmental Economics point out that the Volt gets 230 mpg when the trip length is exactly 51.11 miles, but for a trip of 200 miles the car gets 62.5 mpg, which is not much better than my diesel VW Golf, purchased used for around $15K.” (Note: The Volt will cost approximately $40,000 minus a $7,500 tax credit.)
- Lisa Margonelli, The Atlantic via Environmental Economics

Charge More, Get Better Mileage?

“Tony Posawatz, vehicle line director for the Volt, notes that since the Volt results are based on a single charge per day—and that given the recharge time of 6-8 hours on a standard 110V outlet or half that on a 240V charger, the Volt has the potential to deliver better than 230 mpg performance if it can charge multiple times per day.”
- Mike Millikin, Green Car Congress

And The Winner Is…

“In the future, ‘MPG’ ultimately will be moot.”
- Tony Posawatz, GM’s vehicle line director for the Volt


Posted in EPA Numbers, News
Tagged as ,

Related Readings

  • Mark Torbett

    Condering that this is really a battery usage, wouldn’t you rate the car in Miles per ( amp Hours)? So MPG is out but mile per energy used is not. Many DC powered voltage systems use Amp Hours as a measurement of power available.
    The higher the amps used the lower the hours of available functional use. But, lets be real a DC voltage car just means my Power compnay makes a lot more money. And can you see work letting you plug and charge you car all day at work. And what about the basic issue of Battery cells in very cold climate?

  • crookmatt

    The bottom line is the Volt could make economic sense to some people but not to others. To condem it simply because it doesn’t get sigificantly better gas miliage in every possible situation is silly.

    Those who would use it for around town driving and short-medium commuting would reap the benefit the Volt offers of almost exclusively electric driving, with the option to driver further when needed on occasion.

    Those who would use it regularly or only for long distance driving, would be better off with a high efficiency 4-cyl vehicle once life cycle costs are considered.

    Just like every car, it makes sense for some people, but not for others, no-body is forcing anyone to buy it, so there’s really no reason for Prius owners on this forum to feel threatened by it.

  • What The

    Agreed, it should be set to some miles/kilowatt-hour, this way consumers can turn the miles/kilowatt-hour to miles/dollar, or dollar/mile through simple conversion knowing how much they pay per kilowatt-hour at home, and we can see how much we are really saving by doing the same with our current gas prices.

  • frank feelezer

    Well the volt is the future. Well toyota lost its edge !

    Hybrids are hybrids . the volt is pure electric.

    With the option of using gas if needed.

    So 230 sounds low to me. Remember the volt can use gas

    The Nissan and Tesla cant.

  • Dave121

    Actually no, Volt doesn’t fit ANY one. For short distance commuter, they’d be better off with a Leaf, which supposedly would cost near gas eating peers, according to Nissan. Well, probably good for those driving exactly 51 miles a day. :D

  • Narpati Luthra

    So it turns out that 230 mpg is not for every gallon of gas that you put in, it is (largely) for the first gallon which don’t have to put in!

  • Anonymous

    Even if your electricity comes from a “dirty” source such as a coal-burning power plant, the end product of using an electric vehicle with coal power is much cleaner than using a petrol-powered combustion engine and no electricity from the power grid. This is, of course, ignoring other ramifications of gasoline, such as the need to physically transport gasoline to locations around the US versus sending electricity down a wire., oil transport from locations around the world to the US, and so on.

    Also, a big difference between the Volt and the other hybrids is that the Volt never, ever uses a gasoline engine to actually drive a car forward. It’s an electric vehicle, that can use conventional gasoline to recharge its own battery while on the road. Hybrids on the road now use a gasoline-powered motor and electric-driven motor in tandem to produce motion. This is why that, even on the highway, the Volt will likely travel 500 miles on fewer gallons of gas than say, a Prius over the same distance – even when the Volt’s initial overnight charge was depleted not even 1/10th of the way into its journey.

  • Dan L

    ’230 MPG’ is shorthand for ‘MPG is not a meaningful measure for this kind of vehicle. But our customers will be confused if we use any other measure. So, we’ll just make something up. Oh, and we’ll hide behind the EPA when asked where this obviously made up number came from.’

    This open contempt for consumers’ intelligence seems like a bad idea to me. Then again, I don’t sell cars for a living.

  • Gonealot

    The statement of 230 mpg is correct; that is *if* the 210 mile extension cord is plugged in.

  • Troglodyte

    Surely we need an alternative to mpg as this is a liquid hydrocarbon measure. How about CO2/mile as all energy sources require carbon input right now? Or dollars/mile as all the energy costs something?

    BTW we need to differentiate between half-arsed ‘hybrids’, hydrocarbon/electric with regen-braking, and plugin/hydrocarbon/electric with regen-braking etc. Its unfair to lump all the technologies under the same heading as that sullied by the parallel hybrids.

  • Anonymous

    Perhaps the CPA (consumer protection agency) should have a little chat with the EPA. Shouldn’t the EPA answer to the public? Why would such an important measure in today’s economy as ‘how miles per gallon are determined’ be secret/proprietary?

    I always wonder that when someone takes extreme measures to hide information, whether it’s not because it’s should be a secret, but rather because people would be angry if they knew the truth and it’s something that really ought to be disclosed.

  • Anthon

    I’d rather see operating cost and carbon footprint as measures for comparison, but this may depend on your grid/utility’s energy mix (e.g,. coal, hydro, wind, nuclear,…).

  • Anonymous

    Maybe it means that it takes 1 gallon of gas to make the electricity to charge the battery to run for 230 MPG ? (Assume you have a gas powered generator)

  • steved28

    I think they should look at the entire potential trip length if they insist on using MPG. If the volt has a 10 gallon tank (example only) and the entire distance that can be covered is 600 miles (combined city/highway) then perhaps it should be rated at 60mpg over all. Anything else is fuzzy math.

  • Red Scott

    The folks I know in the Houston Elec Auto Assoc who actually drive EVs daily, when asked “how many miles per gallon does it equate to?” like to answer with “It costs about 2 cents a day to recharge & thats about 60 cents a month, so compare that to what you spend at the gas station. The effect on my monthly electric bill is practically invisible!”

    This eliminates all the tech jargon about converting gallons of gas to joules of energy to watts of power to amp-hours of battery charge to killowatt/hours on the electric bill so they don’t have under-educated news reporters doing the deer-in-the-headlights face and then repeating moronic statements like “230MPG”. The nice folk at Aptera made a remark about “the equivalent of 300MPG” & had to back-peddle after the science-haters misunderstood the source of the number.

  • Charles

    GM (old and new) has referred to the Volt as an extended range electric vehicle. This seems to be the truth. The Volt can run as an EV or a hybrid. Because of the Volt’s dual personality it needs two ratings from the EPA. The first should be a range and consumption rating for EV mode. The second should be an MPG rating for when the batteries start out dead and the Volt acts as a hybrid. I do not know the battery starting status for the current hybrid testing. To be fair all should start out with dead batteries. Also to be fair the test should go for 400 miles or so, not the 50 for the current test. Testing for such short distances will make starting battery charge level a big part of any plug in hybrid.

  • Dean Larsen, San Diego

    GM determined the 230 mpg figure because no one can figure it out and everyone will discuss the fact that no one can figure it out. hmm… that’s exactly what we’re doing in these responses. The Tesla is still the be car (and car company) on the planet. I never want to buy gas again. ;-)

  • Jerry

    Honda Civic has about 54% of the Volt operating cost mostly because the Volt is too costly.
    Calculation Basis: $2.5 gasoline, 15000 miles per year 10000 as Electric, $0.115/kwh at 70% charge efficiency, 8kwhr/charge, $40,000 initial cost, 8% interest, Vs Honda Civic at $22,000, and with depreciation, and repairs typical for the brands 20% vs 15% repairs 3% vs 2%;

    I’m uncomfortable assuming the claimed Volt 62.5mpg rating vs the 30mpg Honda actual value I used.

    Jerry
    (Engineer)

  • Lost Prius to wife

    Charles and Anonymous, per EPA and DOE, the average American still drives approximately 15K miles per year (www.fueleconomy.gov). If the Volt goes forty miles before kicking in the gas engine, this gives one 14.6K miles per year out of the wall and a mere 400 miles from the gas engine (~$28 for gas at $3 per gallon). Therefore, in this case, the electric cost is the majority of the yearly fuel cost. This is also probably the most optimum and optimistic estimate (technically, 1607 mpg). If one would go on a vacation or drive more than forty miles per day, the cost changes upward (not steeply) and the mpg drops. Using the latest given information for the Volt, the first 340 miles would average ~48.5 mpg. Without stopping to recharge, all the next miles beyond the 340 miles would average ~42.9 mpg and require refueling every 300 miles. But this would almost always be the “exception”, not the “rule”. And those numbers are not bad in anybody’s book or budget. This makes the Prius “better” for long distance travelers (traveling 50 miles per day and up), but not everyone is going to be in that category (probably not the majority of people). This means that cost comes into play. While the low end Prius is cheaper, the upper end Prius starts at ~$28K and goes to ~$35K. If the Volt is brought out at ~$40K with the $7500 plug-in credit, the Volt does have a chance of competing against the upper end Prius, especially over a five year period of cost. Since the least number of miles per year for me is 16K+, the Prius still carries a slight advantage over the Volt. But again, I am not “everyone”.

  • suheil

    the main question no body commented on is the battary life the battary is so expensive and will remain so for long time to come so if you put into consideration that you will need a battary down the road after 5 to 8 years if the technology permits then you need to add the battary cost to the equation that will alone eat all the savings you did in the previous years let alone the drop of the car value after thos years because the new buyer will be concern about how much battary lfie is left and how much a new one soon he will have to buy so if car manufacturers didn’t solve this main issue the electric and hybrids will remain uncertine future for the buyer and not a real money saver in the long term they may be for the first years of the car theoritically at least but not for some one who is real about saving and want to keep his car, i am not saying i am not a fan of hybrids or electric or any green product, i am actually one of the very first fans of them but when i got deep in studing them i found they are not till now saving anymoney so manufactureres should do much more in terms of those cars price battary life and costs and if fuel cell is the way to go then this may seems worth more the money and effort to go

  • Lost Prius to wife

    Also, to achieve the “230 mpg” that GM is estimating, one can only go an average of 47.657 miles per day. Anything less than that increases the mpg over “230 mpg” and anything more than that decreases the mpg under “230 mpg”.

  • John10111

    When all these calculations are going on folks are missing the bottom line.
    Instead of paying money at the pump you pay for 200-300 lbs of Lithium every 6-10 years. Link that together with a limited global supply of Lithium of about 300 million 200 lbs batteries…..well that’s about enough for the USA. Add on top once demand exceeds the by-product supply ratio off fertilizers the price is going to skyrocket.

  • DC

    Your exactly right, why do people still believe that Li-on suddendly became the battery of choice for the quasi-EV industry because of its inherent ‘superiority’?

    Does it need more “research”-check
    Is it expensive-check
    Complicated-check
    Hard to recycle-check
    Limited supply of primary raw material-check
    Does it require expensive replacments preiodically-check
    Does it have a proven record in EV’s-Not really(but that never stoped the auto industry before)
    Does it “run down” permanently regardless of weither you use it or not-Check (Li-ons in your notebook do exactly the same thing) Even under ideal storage conditions, a li-on battery will eventually become useless no matter what you do.

    The 6-10 year replacement time frame. that is often thrown out, I have a bit of problem with that #. It may(or maybe not, its possible) far less than that. There is afaik very little real-world data and testing to suggest a large or even small format Li-on would last that long. The only batteries with that kind of longevitey and reliability are batteries like the suppressed Nimh batteries or NiFe. Im not aware of any Li-on, again to use laptops as an example, that would retain there ability to power a notebook after 10 years even under ideal care, so I certainly dont buy into it doing that in EV. So John is completely correct, all the car-companies are looking to do is substitue expensive non-renewable fuel with expensive non-renewable litium, and not only that, if your driveing a hybrid there oil company partners still win, since your still tied to the gas pump. The only battery with the prove reliablty 6-10 years of continuous real-world operaton in full EV’s is the NiHM batery, not lithium

  • Chris M

    The problem with anything based on tank size can be manipulated. I would say that besides the standard EPA info they should publish MPG only running on gas. That would help comparing long trips over the electric range. Cost per mile for average driving would be nice too since that’s what matters in the end.

  • Jerry

    Prius Plugin should have about 51% of the Volt operating cost mostly because the Volt is too costly.
    Calculation Basis: $2.5 gasoline, 15000 miles per year 10000 as Electric for the Volt, 7500 each for the Prius Plugin, $0.115/kwh at 70% charge efficiency, 8kwhr/charge, $40,000 initial cost, 8% interest, Vs Prius Plugin at $24,000, and with depreciation, and repairs typical for the brands 20% vs 15% repairs 4% vs 2%;

    I’ve increased the Volt repairs to 4% due to battery issues. Slightly different missions but the average buyer will use Gasoline 1/3 of the time or more. A negligible few will use them like a golf cart around town only, that’s just silly and sometimes we lazy people or kids won’t even plug them in properly especially for short quick trips where a plugin in may only save 25 cents, besides, many states will tax them on mileage also. Get real!

    Jerry
    (Engineer)

  • Mr.Bear

    You have to assume the gas engine/generator will get at best 50 mpg. That means the other 180 miles have to be driven on battery. Or 10 out of every 13 miles driven are on battery power.

    I’m not sure how realistic that is. Sure, the average commute is 40 miles. Mine is 42 miles. But I do drive other places than roundtrips of work and home. Those drives sometimes extend past 40 miles. I would not bet that I could average 10 of every 13 miles on battery power.

    I said it when it was first announced, “230 mpg is a lie.”. Cool logo, but a lie. And whe. EPA rakes them over the coals and makes them set back to 55mpg or there abouts because that’s the average for using a full tank of gas on a trip, everyone will choose a Prius because it’s $15,000 cheaper.

  • Jerry

    Well, Mr Bear, of course it’s a lie to not disclose all of the misleading facts. It’s really simple to be honest if one tries.
    For the Volt and when on battery the marginal electrical costs are about 3.5 cents per mile and when on gasoline the marginal costs are about 4.2 cents per mile, given 62.5 MPG energy consumption equivalent for both at $2.5/gal gasoline and $0.115/KWHR at 70% charge efficiency.
    The fixed costs for depreciation, interest and repairs for 15,000 miles per year run about 88 cents per mile given 8% interest, 20% depreciation and 4% repairs(including hopefully cheap batteries amortized). Higher annual mileage will reduce the fixed cost per mile but assume gasoline mode due to charge and usage limitations. Thus, 92 cents per mile at 15000 miles, 48 cents per mile at 30000 miles, 26 cents per mile at 60000, and 15 cents per mile at 120000 miles per year. Costs decline with depreciation but repairs will rise with usage.
    Now really, that wasn’t so hard, was it, it just hurts a little to be honest.

  • RKRB

    Here’s another answer: the 230 mpg figure represents a Synergy between two unreliable entities (the government and GM).

    The 230 mpg figure reflects the EPA’s testing methods, but realistically expecting the Volt to deliver 230 mpg for most drivers remains to be seen. It looks more like an attempt by GM to “game” the system, although these days it’s hard to tell where the government begins and where GM ends (and there is a conflict of interest here now that GM is partly run by the government). As previous posters have noted, you still must factor in the cost and pollution of electric power, which is neither free nor green.

    These numbers appear inflated, and do little to improve the credibility of the government or GM. On the bright side, the GM “figure” seems to be making people think about the issue of accuracy. The EPA has some unavoidable constraints — they need to be consistent yet they also need to be flexible, and sometimes consistency and flexibility are hard to blend (September’s Car and Driver has a good article about the EPA’s methodology).

  • Lost Prius to wife

    Mr. Bear, “230 mpg” is not a lie as long as one does not go over the average of 47.657 miles per day. In fact, going less than an average of 47 miles per day produces a “miles per gallon” greater than 230! This is why it is hard to compare EVs, fuel cells, serial hybrids, parallel hybrids, and power split hybrids using just “mpg”. The person that goes exactly 40 miles per day for 364 days and then takes their annual 440 mile round trip to their favorite fishing lake in their Volt just got “1607 mpg” for the gas they used. But their energy cost was greater than the 9.333 gallons they bought for the year. They had to pay for the electricity for the other 14.6K miles. So while “1607 mpg” is not false advertising, it is also not the whole story. DOE and EPA have to decide on a formula that encompasses all the various energy forms and all the different driving habits. That is a very daunting task knowing whatever they decide on will be questioned by everyone as to how and why they did what they did.

  • Lost Prius to wife

    Jerry, I have been enjoying your line of thought and well estimated numbers. Most may think it is too much “overkill”. But my guess is that this will be closer to the route that DOE and EPA will go (along with the rest of us that want to figure out which cars are cheapest for our needs). The “cost per mile”, “cost per 100 miles”, or “cost per 500 miles” energy wise, with a standard of 15K miles per year, is probably the way that cars will be listed, decisions made from, and a definite way of the future.

  • Lost Prius to wife

    Also, Mr. Bear, John10111, and suheil, if I read the article correctly, one will be able to buy the Nissan Leaf, but only lease the battery. This will allow Nissan to compensate for any lithium battery problems or even use metal halides for replacements depending on how the lease is setup. As my best friend pointed out, it could come down to having battery/fueling stations instead of just a gas station. One drives in with an older designed battery, a depleted battery (for someone with an EV that does not want to wait for charging), or a dead cell battery, the car gets put up on the lift, the old battery dropped out, the new charged battery popped in, and off the lift, out the door, and down the road. New better designed batteries would always be available and the older batteries recycled (oh, my, what a concept!). For a new and better future, new concepts are needed and called for.

  • Baltimore Prius Owner

    Let’s see, GM, partially run by our government, fuzzy math, a car that has yet to be produced……………..why is everyone so “up” on this topic? I’m done with it, just as I have been done with GM for years.

    Two Priuses = Loving Life

  • harry stone

    lol all the Pompus people are upset now because they realized their hybrid is now last years technology.

    They will wine and moan for years stating how the prius is so much better than anything to justify the hefty price they paid for a toyota. The problem is prius people have to pay an extra 5k at the dealer to get one.

    hybrid=temporary technology

    Now the Volt that is pure electric is so much more efficient

    well basic electrical engineering tells you

    electric motor = 98% efficient ( volt is pure electric)

    Internal combustion engine = 30% ( pries is a combo)

    So the volt will basically leap way over the pompus people

    and then they will wonder why they paid 35k for a car that only gets 50 mpg.

    The volt is the technology for the next 10 years

  • Jerry

    Well, Harry you seem to have have axe to grind. For me caring an axe like a Neanderthal gets in the way of bottom line honesty. Both the Volt and the Plugin Prius are next year cars and most valid for comparison.
    What you left out was the cost of hauling all those heavy batteries, the risk of them catching fire, especially in an accident, the replacement and disposal cost, and more important the battery charging and discharging efficiency(based upon my estimates to be improved as facts warrant) of 90%charger x70%Batteryinx70%batteryout
    x98%converter x 90%motor = 39%Overall
    Wow, Electrical systems have a lot of losses also.
    The most valid way of comparing is by using fixed mileage cost plus variable mileage cost for both electric and fuel operations using honest figures for fuel, electricity cost, interest, depreciation, and repairs(wbattery). Refinements can include taxes and projected mileage for individual local conditions.
    These calculations can easily be done on a spreadsheet or a website.
    By the time the Volt is out, given Chevy’s bad marketing development and cost control records, other companies will be in there like “biting sows”. Nowadays, the future contest is not as fully decided by illusions from dishonest marketing groups but more so by honest engineering and facts. (The Neanderthals may still buy the high margin illusion, but the tech savvy will not.)

  • Skeptic

    Repeat after me:

    THE CHEVY VOLT IS A PLUG-IN HYBRID.
    THE CHEVY VOLT IS A PLUG-IN HYBRID.
    THE CHEVY VOLT IS A PLUG-IN HYBRID.
    THE CHEVY VOLT IS A PLUG-IN HYBRID.
    THE CHEVY VOLT IS A PLUG-IN HYBRID.

  • Skeptic

    “the risk of [batteries] catching fire, especially in an accident”

    ROTFLMAO!

    Question: Which is more likely to be a “problem” if your vehicle is wrecked and catches fire?

    A) 15 gallons of gasoline

    B) a few hundred lbs of batteries

    As for replacement and disposal costs … well, the batteries may be expensive to replace (but cheap to charge), but it seems the gas tank takes a lot to “recharge” even if it does have a longer lifespan.

    Disposal issues after use? Well, you breathe the fumes from your ICE, you tell me which you’d rather deal with.

  • Jerry

    As noted, the Prius plugin and Volt are plugins. That’s why I compared them. The battery comment was intended to imply that I trust Toyoto’s current battery technology while due to Chevy’s past performance, I’m less sure of safety issues until they actually have a marketed performance rather than their usual marketing nonsense. Show me don’t sell me.

  • MarkW

    See SAE J1711 as the most likely candidate for the EPA’s PHEV testing rule and in particular Argonne National Laboratory’s work on this standard.

  • Bill

    Where I live it costs almost two cents a day to run a 1600 watt hair dryer for five minutes. Sounds like some EV users are as prone to exaggeration as some car owners/manufacturers.

  • Victor

    GM got the missleading 230mpg as follows:

    Off peak cost of electricity: 5.0 c/kWh
    Average cost of Gasoline: 2.55 $/Gal

    So $2.50 buys 1 gallon of gasoline or 51 kWh of electricity.

    if 8.8 kWh of electricity gives 40 miles of city driving
    Then 51 kWh gives about 230 miles.

    For the cost of 1 gallon of gas you get 230 miles of electrical driving. This is missleading and depends a lot on the cost of gas and of electricity.

    A better calculation is:

    1 Gallon of gas: 130 MJ of energy
    1 kWh of Electricity: 3.6 MJ of energy

    So 1 Gallon of Gas = 130/3.6 = 36 kWh of electricity EQUIVALENT

    if 8.8 kWh of electricity gives 40 miles of city driving
    Then 36 kWh gives about 163 miles.

    The Volt will have a REAL electrical mode ENERGY efficiency of: 4.54 Miles/kWh or 163MPG EQUIVALENT.

    Although the energy comparisson is correct and realistic, the economic one from GM may be more meaningful for the actual user.

  • Daniel F

    This is a great idea, I would love the idea of pluging my car at home to get the maxium mialage possible, all i do is ten to Twelve miles a day. This will be great if gas rationing happens again. Baby boomers will never forget the gas shortage in the 1970s also with gas and electric combined with 50+ a gallon how can you go wrong, its a no-brainer. All I’m waiting for is for the Prius from Toyota to add a plug feature to their hybrid so i can get an extra 10 to 15 miles more per day that is the extra i am waiting for! It would be my dream if they added solar cells to the roof of the car that trickle charged the batteries for an extra 10 or 15 miles a day who cares if the sun does not shine every day every other day is fine with me, i know they have solar cells now but they use it for a fan to keep the car cool when parked, I would rather keep my windows cracked open and reap extra mileage. Adding mileage to the car is key. That is what baby boomers want!

  • Ramiro

    I agree, “the power company would make more money”… but our efforts are bringing a new and exciting technology to fruition – and to the detriment or betterment of same. Who would of thought, a self generating Pure EV. Thanks for your comment. rc