GM Claims a 230 MPG Volt — Is it For Real?

General Motors made a media splash this morning by announcing that its Chevy Volt would get 230 miles per gallon in city driving, but the claim quickly began proving little more than a broad estimate.

chevy_volt_230mpg.03.jpgThe stage for GM’s announcement today. (Photo: CNN)

GM based its Volt claim on draft rules from the Environmental Protection Agency (EPA). The agency promptly noted that the 230-mpg estimate — which does not include less fuel-efficient highway driving — could not be confirmed in a statement to the AP.

So how did GM obtain its eye-popping number? The plug-in hybrid Volt can travel for 40 miles using electric battery power before switching to a gasoline engine as it recharges. The 230-mpg estimate comes from an assumption that the majority of drivers would travel in the neighborhood of 50 miles per day.

As the distance traveled rises, the Volt’s fuel-efficiency would shrink, as CNN points out: a 300-mile trip would get about 62.5 mpg. (Electric high-speed rail in Europe, by contrast, gets upwards of 300 passenger-miles per gallon for trips of a similar distance.)

In an unwitting illustration of the car’s uncertain efficiency, the Washington Post’s Green blog headlined one post: "The EPA Gives Could Give the Chevy Volt a 230 MPG Rating. What?"

Regardless of its veracity, the 230-mpg claim gives GM the new marketing tool it craves to help boost its prospects of repaying $50 billion in government loans by 2015. Whether Volt sales will begin sales next year as planned, however, remains to be seen.

In a regulatory update filed last week but caught by Bloomberg, GM admitted that the plug-in hybrid technology "has not yet proven to be commercially viable." GM continued:

Our competitors and others are pursuing similar
technologies and other competing technologies, in some cases
with more money available There can be no
assurance that they will not acquire similar or superior
technologies sooner than we do.

  • Kenney

    From the NYT article:

    “Another issue that G.M. and Nissan are struggling to figure out is how to accommodate people who live in an urban area or an apartment without a garage and cannot easily plug in an electric car, yet could benefit the most from one.

    ‘If you’re going to park it on the street, I don’t know what to do actually,’ Mr. Henderson said. “I don’t know how to address that situation.'”

    That’s a HUGE “I don’t know.” And in general, the progress that GM and Nissan have made has many important ramifications for transportation. Not least among them, is the fact that with this progress, the gas tax must be given the boot, and serious investment in and public education of a non-intrusive VMT must be in the works ASAP.

    There are several other consequences connected to the investments that GM is making, but what I really want to know is why aren’t they making buses and trains? It just seems so silly that much of the resources of the “new” GM are going into fuel-efficient vehicles when the technology and know-how already exists to make rolling stock. Henderson’s “I don’t know” on the question of VOLTs owned by non-garage having urbanites is just emblematic of the auto company’s inexplicable aversion toward considering mass transit as a part of their game plan. Businesses exist to make money…diversify already!

  • I work with the Volt communications team. First and foremost, there is nothing GM foresees at this time that would result in a delay of the Volt.

    The statements in question are posted in the “Risk Factors” section of GM’s SEC filing made last Friday. These statements are intended to inform potential investors of risks associated with GM’s plans and strategies. The statements are just one small section of the filing – other sections of the filing highlight our plans and intentions to further lead in the electrification of the automobile.

  • garyg

    With respect to a comparison to mass transit, it doesn’t really matter whether the Volt’s urban-driving fuel efficiency is 230 mpg or “only”, say, 100 mpg. Even at 100 mpg, it still blows the efficiency of mass transit out of the water. Bye, bye buses and trains.

    I don’t understand the point of Elana’s comparison of the Volt to high-speed intercity rail. Intercity travel isn’t really the Volt’s target market. It’s much more efficient than conventional cars even for intercity travel, but where it will really shine is in everyday commuting and urban/suburban driving.

    By the way, I’d love to know where the figure of 300 passenger-miles per gallon for European high-speed rail comes from. Elana links to a Wikipedia article, but no source is given for the number. And comparing vehicle mpg to passenger mpg is apples and oranges. A Volt with 5 passengers that gets a vehicle mpg of 62.5 on a 300-mile trip would get a passenger-miles per gallon of over 300.

    The Times article also mentions an upcoming all-eletric car from Nissan, the Leaf, which is expected to get even better mileage than the Volt – 367 mpg.

  • garyg: The high-speed rail number comes from averages for France’s TGV, which run the comparable stretch from Paris to Lyon with an 80% load capacity at 18 kWh/km, and assumes a per-kWh cost of about 10 cents. Also, it should be noted that the 62.5 mpg number doesn’t include the electricity used to charge the Volt’s 16 kWh battery for the first 40 miles.

  • garyg

    Elana, where are you getting your numbers about the TGV from? They’re not in the “dkosopedia” article you link to. Please provide a link.

  • I don’t have a problem with their 230 mpg claim. It is apples to oranges, clearly, but the thing you have to realize is that people are currently irrationally afraid of a daily milage cap that comes from an all-electric vehicle. In the face of irrational fear, a bad analogy is one way to educate.

    It is important to get a plug-in electric out in the field quickly, so that people realize that 40mph isn’t much of a cap at all. Yours truly rides his bicycle all the time, and although there is no milage cap per-se, 40 is way more than I need to get things done. Once people realize that they can adjust their behavior to get under the milage cap, then you’ll start to see two great things happening: people driving less, and cars without the stupid generators. The latter will make people tougher on other polluters. That’s all good.

  • Don’t bother chasing down those TGV numbers. The 230 mpg calculation for the Volt doesn’t account for electricity use. By this math any electrified rail, from intercity to subway, already and always has an infinite mpg. As the Blue Book guy says in the article:

    “It almost becomes an abstract number. If you are the Volt target guy who is driving under 40 miles per day, then theoretically your miles per gallon is infinite.”

    ‘Almost’ is a wildly unnecessary qualifier here. The number is in fairyland.

  • garyg

    Nathan H,

    You are confused. The EPA methodology accounts for electricity use by converting it into an mpg-equivalent. How do you think they generate mpg figures for all-electric vehicles?

    The press release reports that: “At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.”

    That’s about a quarter of the fuel cost of a conventional midsize sedan, at current gas prices. If gas prices increase, the price advantage of the Volt will also increase.

    But in fact, since most recharging will probably be done at night, using cheaper-than-average off-peak electricity, the typical cost may be even less than 3 cents per mile.

  • It’s possible that both I and the editorial director of Kelley Blue Book that are confused in our assumption that normal math (divide by zero) and normal terms (gasoline) being applied. But if the Volt’s cost of operation is quarter that of a midsize sedan, why is the concocted mpg figure ten times instead of four times that of a midsize sedan? It’s hard to say who is smoking what; I will admit to some confusion on that point. The EPA should be producing standardized cost of operation figures, miles per dollar, not cranking out miles per gallon (of what?) ratings for electric cars. That’s just marketing.

  • garyg

    But if the Volt’s cost of operation is quarter that of a midsize sedan, why is the [estimated] mpg figure ten times instead of four times that of a midsize sedan?

    Because the 3 cents per mile figure refers to an estimate based on the “average” national cost of electricity and the “typical” usage pattern (a mix of city and highway driving), whereas the 230 mpg estimate refers to city driving only and the expected cost of the electricity that will actually be used for recharging. Most Volt owners will probably do most of their recharging at night, when electric rates are much lower than the average (in the case on my utility, the off-peak rate is only one-fifth the on-peak rate).

  • garyg

    The EPA should be producing standardized cost of operation figures, miles per dollar, not cranking out miles per gallon (of what?) ratings for electric cars.

    The standard EPA fuel economy label contains the following information:

    – Estimated MPG average and expected range for city driving

    – Estimated MPG average and expected range for highway driving

    – Estimated MPG average for combined city/highway driving (I think they assume an average city/highway mileage ratio of 60/40)

    – An illustration of where the estimated fuel economy for this vehicle falls within the range of all vehicles in the class (compact, midsize, full size, truck, SUV, etc.)

    – Estimated annual fuel cost, at a stated annual mileage (the national average) and price-per-gallon for gas.

    It also states clearly “Your mileage may vary” and gives the EPA fuel economy website address for further information.

    This seems pretty good to me. Your request for an EPA “standardized cost of operation” estimate doesn’t make much sense given that that would include the cost of things like tires, maintenance, insurance, registration, etc. that are not in the EPA’s brief. I believe AAA publishes annual cost-of-driving estimates for different models and classes of vehicle.

  • “Because the 3 cents per mile figure refers to an estimate based on the “average” national cost of electricity and the “typical” usage pattern (a mix of city and highway driving), whereas the 230 mpg estimate refers to city driving only and the expected cost of the electricity that will actually be used for recharging.”

    City driving is one thing. It is quite another to have a different set of electricity price assumptions between the two numbers. Why do this? Not everyone has lower rates of electricity at night, and further, these off-peak discounts will be driven down as more people charge batteries at night. I don’t fund the EPA to have it assume best case scenarios—and, I’m far from convinced that is the particular bad methodology they used to get to 230. You may believe the Volt will have one tenth the energy cost of a 23 mpg gasoline vehicle, but for most people this figure is just incredible enough to exclude from a $40,000 purchasing decision. It will help get them in showrooms and generate buzz, but that’s not something the EPA is charged with either.

    “doesn’t make much sense given that that would include the cost of things like tires, maintenance, insurance, registration, etc. that are not in the EPA’s brief.”

    Their brief will have to change with the technology if they are to provide any value to the public. Electric vehicles have a different set of costs, like battery replacement, that people will have a hard time factoring in until they have owned one. A comprehensive report would provide separate indices for gasoline and electricity use, an overal energy cost estimate at current utility rates (which could be easily updated, or localized, with a simple web calculator), and a maintenance cost per mile for parts that are guaranteed to wear out like tires and batteries. This would be a service to the public. Saying a primarily electric powered vehicle gets 230 miles per gallon of gasoline is not.

  • garyg

    Nathan H

    If you would read the press release and note carefully what each number refers to you might not be so confused. The EPA will provide city, highway and combined estimates for the Volt, just as it does for conventional vehicles (and current hybrids like the Prius). Electricity prices vary somewhat across the country, just like gasoline prices, so it’s not possible to provide a single number that applies to all drivers. The EPA fuel economy information can only be, and is only intended to be, a broad average estimate of fuel costs, not an exact figure.

    That said, on the basis of the numbers reported yesterday, and at current gas prices ($2.50 – $3.00 per gallon) Volt owners who operate the vehicle in the same way as a typical conventional midsize sedan can expect fuel costs on the order of one-quarter the costs of the conventional vehicle. Volt owners who operate the car primarily as a city car, with little or no highway driving, can expect fuel costs on the order of one-eighth to one-tenth the costs of the conventional vehicle.

    If gasoline prices increase, the fuel cost savings of the Volt will also increase.

  • Again I must remind you that by your reckoning a quoted source for the Times article would alos have to be “so confused”. Perhaps you should spend some words trying to belittle the Blue Book editors, whose knowledge of EPA standards can not compare with what you may glean from a GM press release. I would like for my government agency explain this outlandish number itself, but there doesn’t seem to be anything up-to-date on their standards page: http://www.epa.gov/fueleconomy/regulations.htm

    Unless you have some direct evidence that this miles per gallon of gasoline figure tries to account for the electricity input, in some necessarily ham-handed way, there isn’t anything to talk about on that point. However they came up with it, the result is absurd. No 2009 Accord gets even 23 EPA city mpg, so, the official indication is that on average the Volt’s energy cost per mile of city driving will be less than 1/10th an Accord’s. Poppycock.

  • garyg

    Nathan,

    Yes, I think the Kelley Blue Book guy is also confused. A Volt that was operated on battery power only would not get “infinite” miles per gallon under the EPA methodology. It would get some finite mpg calculated from the amount of electrical power it consumed per mile using a value called the “petroleum equivalency factor.” This is also how a mpg figure will be calculated for all-electric vehicles like the Nissan Leaf.

    The EPA describes its Petroleum-Equivalent Fuel Economy Calculation here:
    http://www.epa.gov/fedrgstr/EPA-IMPACT/2000/June/Day-12/i14446.htm

  • Here’s a senior writer for CNNMoney.com that would also have to be so confused, along with his fact checkers, about GM’s claimed mpg not accounting for electricity inputs:

    “When gasoline is providing the power, the Volt might get as much as 50 mpg. But that mpg figure would not take into account that the car has already gone 40 miles with no gas at all.

    So let’s say the car is driven 50 miles in a day. For the first 40 miles, no gas is used and during the last 10 miles, 0.2 gallons are used. That’s the equivalent of 250 miles per gallon. But, if the driver continues on to 80 miles, total fuel economy would drop to about 100 mpg. And if the driver goes 300 miles, the fuel economy would be just 62.5 mpg.”

    http://money.cnn.com/2009/08/11/autos/volt_mpg/index.htm

  • garyg

    Yes, he is confused too. In fact, he’s making the very error you falsely attributed to GM (not accounting for the use of electricity in the mpg calculation).

    I don’t know why you continue to dispute this point. I just gave you a link that describes in detail the EPA methodology for converting electrical energy into an mpg-equivalent. This is the methodology GM used to produce its fuel economy estimate. It’s not an official EPA number. The EPA will do its own independent testing when the final production version of the Volt is ready. But unless GM has made a significant error, or the EPA significantly changes its methodology before the Volt goes on sale, the numbers provided by GM earlier this week are likely to be close to the official EPA fuel economy rating.

  • Nathanael Nerode

    garyg wrote: “Even at 100 mpg, it still blows the efficiency of mass transit out of the water. Bye, bye buses and trains.”

    Well, no.

    Electric rail gets higher efficiency than that, by large factors, when it’s even half-full. On top of that, it can go faster, and it’s not subject to slowdown due to congestion during rush hour. The Volt is no substitute for urban electric rail, whether subways or streetcars, and it is no substitute for high-speed intercity rail.

    However, it does blow away buses, and probably any other form of transport in an *uncongested* area with a speed limit of 75 or less. Given that I live in a small, relatively uncongested town, it’s perfect for people like me.

  • garyg

    Nathanel Nerode,

    Well, no. Electric rail gets higher efficiency than that, by large factors, when it’s even half-full.

    The latest edition of the Department of Energy’s Transportation Energy Data Book reports the average energy intensity of passenger cars as 3,514 BTUs per passenger-mile and the average energy intensity of rail transit as 2,577 BTUs per passenger pm. At 100+ mpg combined, the Volt is more than four times as energy efficient as the average passenger car. So expressed in BTUs, the energy intensity of the Volt is on the order of 879 BTUs per passenger-mile.

    In other words, it blows the energy efficiency of rail transit out of the water.

    In other words, you’re wrong. Even a Toyota Prius beats rail transit.

    In fact, even this understates the huge efficiency advantage of the Volt, because the 100+ mpg figure is for combined driving. For city driving, the estimated efficiency of the Volt is over 200 mpg. That’s about SIX TIMES more energy-efficient than rail transit.

  • Graham Katz

    No nope no way. Unfortunately garyg has gotten himself tripped up in the very complicated issues that surround comparing fuel-burning vehicles and electric vehicles. What do you compare? The energy used to turn the wheels? The energy used to produce the electricy (the “primary” energy)? How should we measure it? It is tough to know, and there is plenty of discussion of it elsewhere . Certainly the confusion around this (and the even more confusing treatment of “virtual MPG” for electric vehicles that the EPA has introduced) could lead anyone astray.

    But there is no need to go there. If you want to compare rail transit with the Volt, you can do it directly. According to this posting Volt uses .25 kWh to go a mile. Its a four-seater, so that translates to:

    Volt: 62.5 Wh/seat-miles

    Numbers reported here for modern European systems show a Light-rail vehicle to use 15 Wh/seat-mile and a High-speed rail vehicle to use 55 Wh/seat-mile. Closer to home, this report describes BART’s railcars, the newest of them use about 3,300 Wh/car-mile. Cars have 64 seats and can hold 150 at crush load. This means:

    BART: 50 Wh/seat-mile (22 Wh/person-mile at crush)

    Volt certainly doesn’t stack up against any of *these* rail vehicles. If there is any “blowing out of the water” it goes the other way.

    But what about in terms of “real” transportation. Neither trains nor cars are always full all the time. Maybe that is where the Volt can shine.

    Car occupancy rates average about 1.2, so we could expect on average transportation energy use for the Volt in day to day use to be:

    Volt (system): 208 Wh/passenger-mile

    Now let’s go back to BART. The entire BART system uses about 300 million kWh of electricity and provides about 1.3 billion passenger miles of transportation. This gives a system day to day energy use of:

    BART (system): 230 Wh/passenger-mile

    In other words Volt will, if it is as efficient as promised, use about the same energy on a passenger-mile basis that BART uses. (Of course BART is getting on in the years, and that report I linked to is all about how modern retrofitting could reduce BART energy use by about 43%, i.e. to about 132 Wh/passenger-miles)

    So what happened to garyg’s calculation? And why, when you convert numbers above (at 1 kWh = 3,414 BTU), do you only get 750 BTU/pass-mile for BART, when everywhere you read (for example here ) it will tell you that BART (and rail transit in general) uses energy at a rate more like 2,250 BTU/passenger-mile?

    Well that takes us back to the complexity. Those numbers are about _primary_ energy. To back-calculate from real energy use to _primary_ energy use, you are supposed to take into account the efficiency of generating electricity from oil (about 33%). Simply multiply the actual energy use from above by a factor of 3 (to reflect how much oil would be needed to generate the 230 Wh/passenger mile that a BART train actually uses) and you will get that 2,250 BTU number (never mind that in California about half of this electricity doesn’t come from burning anything).

    You can do the same for the Volt, *its* _primary_ energy use is 2560 BTU/vehicle-miles (or 2133 BTU/passenger miles). Not bad compare to an average of 3500 BTU/passenger-mile for today’s car fleet. But not four or six times better.

    PS. The actual energy use of European electric railways, as summarized here (on page 9) is about 150 Wh/passenger-mile. System wide. Including High Speed Rail. (That is about 1500 BTU/passenger-mile in _primary_ energy).

  • garyg

    Graham Katz,

    Your analysis is very confused, and your conclusion is false.

    First, a seat only provides useful transportation when it is occupied by a passenger. So seat-mile comparisons tell us nothing about the real-world energy efficiency of different transportation modes. The correct metric is energy consumption per passenger-mile.

    You claim “car occupancy rates average about 1.2” but you give no source for this number. The 2001 National Household Transportation Survey found an average vehicle occupancy per vehicle-mile for personal vehicles of 1.6 (Source (1), Table A-14). The latest edition of the Transportation Energy Data Book reports an average vehicle occupancy for passenger cars of 1.57 (Source (2), Table 2-12). Using the lower of these two numbers, and your figure of 0.25 kWh/vehicle-mile for the Volt, yields an energy efficiency for the Volt of 159 Wh/passenger-mile.

    You claim that “the entire BART system uses about 300 million kWh of electricity [per year].” Again, you give no source for this number. I’m guessing that you got it from the table on Page 4-1 of the PG&E document you link to. But that number does not refer to the energy consumption of the entire BART system. It refers only to the energy consumption of BART railcars. It does not include energy consumed by BART stations, control systems, track lighting, and so on. BART stations and other facilities are reported to account for 25% of the BART system’s total energy consumption (Source (3), Page 90). The number you give also does not seem to account for energy losses in transmission through the power rail. But including the energy required for stations and facilities alone increases the total to 400 million kWh. At 1.3 billion passenger-miles per year, that yields an energy efficiency for BART of 308 Wh/passenger-mile.

    These numbers indicate that the Volt, when running on battery power, is twice as energy-efficient as BART. According to the Department of Energy (Source (2), Tables 2-18 and 2.19), heavy rail on average is about twice as energy-efficient as light rail. And BART is one of the most efficient heavy rail systems in the country.

    So the Volt is MORE THAN TWICE as energy efficient as the average heavy rail transit system, and MORE THAN FOUR TIMES as energy efficient as the average light rail transit system.

    As I said, the Volt blows the energy efficiency of rail transit out of the water.

    And that’s just for a first-generation plug-in hybrid. Later models, and pure electric vehicles like the Nissan Leaf, will be even more efficient.

  • garyg

    Sources:

    (1)

    (2)

    (3)

  • Jym

    =v= Gotta love these apples-to-kumquats comparisons. Amongst the many things that make BART more energy-consuming than a commuter rail line needs to be is the fact that it’s designed to facility car-based sprawl. Yet are we even considering the impact of the roads the Volt requires, or ON the roads the Volt required? Of course not.

    I’m sick of this bogus 230mpg claim. We are somehow to believe the impact of generating electricity has no “gallons,” presumably because every Volt owner will scrupulously charge off-peak (yeah, right) and more to the point, because there’s an infinite amount of off-peak electricity to be had.

  • garyg

    Yet are we even considering the impact of the roads the Volt requires, or ON the roads the Volt required? Of course not.

    We’ve been discussing operating energy efficiency. We haven’t addressed the energy required either to build roads or dig subway tunnels.

    I’m sick of this bogus 230mpg claim. We are somehow to believe the impact of generating electricity has no “gallons,” presumably because every Volt owner will scrupulously charge off-peak (yeah, right) and more to the point, because there’s an infinite amount of off-peak electricity to be had.

    Incomprehensible. There’s obviously an impact to generating electricity, whether it’s used to power BART trains or to recharge the battery of a Volt. But on the basis of the numbers given above, the Volt provides about twice as much transportation per unit of electrical energy as BART.

  • CBrinkman

    The energy math is beyond me – but I do know that my vision of the future for my city includes fewer cars, not simply replacing the current cars wtih energy efficient models.

    All the energy talk misses a lot of societal impact – the health impact on a front door to car door lifestyle, the space impact of parking all those energy efficient cars, the cost to our city in responding to and cleaning up after car crashes and taking care of the injured, the cost of deaths. Just because a car is energy efficient doesn’t make it suddenly safe or decrease the costs to society of supporting it.

  • garyg

    The subject of Elana’s post is energy efficiency. Specifically, the efficiency of the Volt. With respect to your point about the costs of cars in general…yes, cars have costs. They also have benefits. Given the extent to which our society has embraced cars, most people seem to think the benefits are worth the costs.

  • Jym

    =v= We are encouraged to think of EVs in terms of a best-case scenario in which they’ll always scrupulously be recharged at night, from idle capacity, at lower cost and supposedly causing no additional emissions. I’ve met a number of EV early-adopters and every last one of them felt entitled to top up their batteries whenever it was convenient for them. Of course they had the usual rationalizations.

    The PHEV crowd fancies itself a bunch of stickin’-it-to-The-Man rebels, valiantly going out there and risking everything (or, at least, invalidating their warranties) to get cheap! cheap! electricity in their hybrids. So I’m not exactly envisioning them doing the idle capacity thing, either.

    When it comes time to think about how well this scales up, we just get lot of handwaving. Oh, we’ll get more renewable sources online. Oh, we’re just one technology breakthrough away. Oh, this. Oh, that. Oh, anything but actually trying to tally up the numbers.

    Convert enough cars to electric power and you no longer have idle capacity. You get higher costs and even higher emissions.

  • garyg

    The benefits of EVs and PHEVs do not rest on a “best-case scenario” of driving and recharging behavior by their owners. They are much more energy efficient than conventional vehicles even under operating conditions that are far from ideal.

    And yes, if we don’t increase our electrical generating capacity, and the number of EVs/PHEVs grows indefinitely, they will eventually consume all current idle capacity. But we are long way from that point, and there’s no reason to think we will not increase capacity to meet the increase in demand. The point is that it’s a lot cheaper and greener to power a car by electricity than by gasoline.

  • And finally we know for sure that GM is itself the ‘confused’ party, advertising a 230 mpg figure that does not account at all for electricity:

    “There will be on the label itself an accounting for the gasoline equivalent of KWH used. That’s a separate conversion that will get melded in another way and is not included in the MPG estimate.”
    –Larry Nitz, GM’s executive director of hybrid powertrain engineering
    http://gm-volt.com/2009/08/12/how-the-volts-230-mpg-designation-was-calculated/

  • garyg

    He’s talking about the MPG estimate that will appear on the EPA fuel economy label, Nathan. Not the MPG estimate that GM gave last week. You seem to have missed this:

    “It was a snapshot in time and based on this dataset we will weight the value on an aggregated probabilistic way what the value of the EV distance is, and we’ll also weight one minus that for the charge sustaining distance. You go through this calculation that accounts for the fuel use and you come out with a number and the number is 230.”

  • Nathanael

    You claim “car occupancy rates average about 1.2” but you give no source for this number. The 2001 National Household Transportation Survey found an average vehicle occupancy per vehicle-mile for personal vehicles of 1.6 (Source (1), Table A-14). The latest edition of the Transportation Energy Data Book reports an average vehicle occupancy for passenger cars of 1.57 (Source (2), Table 2-12). Using the lower of these two numbers, and your figure of 0.25 kWh/vehicle-mile for the Volt, yields an energy efficiency for the Volt of 159 Wh/passenger-mile.

    You claim that “the entire BART system uses about 300 million kWh of electricity [per year].” Again, you give no source for this number. I’m guessing that you got it from the table on Page 4-1 of the PG&E document you link to. But that number does not refer to the energy consumption of the entire BART system. It refers only to the energy consumption of BART railcars. It does not include energy consumed by BART stations, control systems, track lighting, and so on. BART stations and other facilities are reported to account for 25% of the BART system’s total energy consumption (Source (3), Page 90). The number you give also does not seem to account for energy losses in transmission through the power rail. But including the energy required for stations and facilities alone increases the total to 400 million kWh. At 1.3 billion passenger-miles per year, that yields an energy efficiency for BART of 308 Wh/passenger-mile.

    ….and you just went apples-to-oranges. You lose. If you do this, you also have to make sure you figure in the energy use of parking lot lighting (among many other things!) into your Volt computation. I’m fairly sure the volt numbers are post-battery energy usage, and the battery losses are actually the largest loss in the system (comparable to losses along transmission lines for rail), which makes it even more apples-to-oranges

    Either you’re comparing vehicle-to-vehicle, or you’re comparing system-to-system, and you did neither. Either you’re comparing engine-to-engine, or you’re comparing powerplant-to-powerplant, and you did neither. Go back to using honest comparisons, and again, BART comes out more efficient than the Volt — *when it has good load factors*.

    On top of that, you’re using a funny comparison, comparing the most up-to-date electric car with a random 30-year-old rail system with some infamously low-ridership suburban extensions, rather than with something modern and appropriate for mass transit.

    Not that your confusion about this even matters to the conclusion, because a fleet of Volts would just be stuck in traffic trying to get across the Bay Bridge, and BART isn’t. Mass transit is appropriate where there’s a mass to transport, a lot of people to aggregate; electric cars are suitable where there *isn’t*.

    And there are plenty of places and routes where there isn’t. Single-family-home garage land, with uncrowded streets and diffuse traffic, needs the Volt. Manhattan and San Francisco don’t, they need electric transit.

  • Nathanael

    Sorry about the blockquote messup — my writing begins with “…and you just went apples-to-oranges”

  • garyg

    If you do this, you also have to make sure you figure in the energy use of parking lot lighting (among many other things!) into your Volt computation.

    Automobile parking lots are used for storage, not operation. The analogy for BART would be facilities where trains are stored when not in operation. The energy consumed by BART stations, in contrast, is required for operation — lighting, elevators, escalators, ventilation, ticketing, etc. In any case, you’re quibbling. BART stations and other facilities consume around 25% of the total energy requirements of the BART system. There’s no way parking lot lighting uses more than a minuscule fraction of the energy required for automobile propulsion.

    On top of that, you’re using a funny comparison, comparing the most up-to-date electric car with a random 30-year-old rail system

    Huh? The comparison between the Volt and BART was made by Graham Katz in his comment #20. I responded to that comment. And BART is one of the most energy-efficient rail transit systems in the country. If even BART cannot match the Volt’s efficiency, rail transit in general is even less competitive with the Volt.

    Mass transit is appropriate where there’s a mass to transport, a lot of people to aggregate; electric cars are suitable where there *isn’t*.

    Another strange comment. Hundreds of thousands or millions of people commute by car in each of America’s major metropolitan areas every day. That’s not a “mass” of people?

  • Graham

    When people ask: “How efficient ARE those trains anyway?” they are
    typically asking about the vehicle efficiency. They want to know
    answers to questions like “What if we all rode electric trains instead
    of cars?” Or “What if we built a new high speed electric train?” Or
    “What if I take the train to work today instead of drive?” Answers concern
    seat-mile efficiency.

    Of course it is reasonable to point out that vehicle load plays an
    important factor in system energy efficiency. Super-efficient trains
    that are nearly empty are not efficient at all. Nor are super
    efficient single-passenger cars. Which is why I displayed energy use
    on both a per seat mile and a per passenger mile above.

    On vehicle occupancy: The average for commuter trips of 16-20 miles is
    1.11 (Numbers from here
    ). These are the trips Volt is designed for. Not “pack the family in
    the car and drive to Arizona” trips. Up this to 1.2 to account for other
    trips (don’t forget that since we are comparing to transit, we need to
    discount “taxi” trips – dropping off the kids at school is not
    transportation for the driver!).

    Of course this comparison is sort of silly to start with: we simply don’t
    know what real the real energy consumption of a Volt or any electric
    car in real day to day-to-day driving will be. I’m willing to take a
    bet that in 5 years the actual energy efficiency of electric cars on
    the road is worse than the actual energy efficiency of the BART
    system.

    And either way, the fact remains that the Bay Area resident who trades his SUV for a Volt is doing way less to save energy than the one who sells her SUV and takes BART.

  • garyg

    On vehicle occupancy: The average for commuter trips of 16-20 miles is
    1.11 (Numbers from here). These are the trips Volt is designed for.

    No, the Volt was not designed for commuter trips of 16-20 miles. It was designed as a general-purpose midsize sedan. But on the basis of the energy consumption numbers you yourself provided, even at an average occupancy of 1.11 the Volt still beats BART on energy efficiency when used in battery-depleting mode. And the Volt is just a first-generation PHEV. And BART is an unusually efficient rail transit system. The Volt beats rail transit in general by an even wider margin than it beats BART.

    And either way, the fact remains that the Bay Area resident who trades his SUV for a Volt is doing way less to save energy than the one who sells her SUV and takes BART.

    The transportation choices of a single individual have only a negligible effect on total energy consumption. What matters is the behavior of people in the aggregate. And in the aggregate, electric and PHEV vehicles beat the pants off rail transit.

  • Graham

    I don’t know if Nathanael is still reading, but his point remains:

    BART wasn’t designed to be energy efficient (it was designed before
    OPEC came into being, when gas was 38 cents a gallon). I compared the
    Volt to BART because I had seen this report (my actual
    numbers on energy efficiency were from the
    national transportation database
    ), which outlines some simple steps
    that could be taken to reduce BART system energy use to about 132
    Wh/passenger-mile (about the average of the Swiss national rail
    system).

    But I’ll grant garyg this: If everything goes as advertised Volt drivers will use (per passenger-mile) 2/3 the energy that the current BART system uses (per passenger-mile).

    So why doesn’t this mean that you should stop riding BART and start driving a Volt to work? Because average energy use is not marginal energy use. Adding ridership to a transit system such as BART (or taking it away) only increases (or decreases) the energy used by the system a little – the marginal amount (not the average amount). This report estimates that the marginal energy use associated with adding ridership to BART is 100 Wh/passenger-mile on average – 41 Wh/passenger-mile at rush hour. Even filling all the seats of a Volt doesn’t make it that energy efficiency.

    So if you are really serious about saving energy you will use transit whenever possible and encourage your friends to do the same. And then maybe buy a Volt.

  • garyg

    Graham,

    I think you have lost track of the discussion. The issue isn’t marginal energy use; it’s total energy use. I argued that, on the basis of the energy efficiency estimates provided by GM, the Volt is more energy efficient than rail transit, when used in charge-depleting mode. You responded by comparing the Volt to a particular rail transit system (BART) that is much more energy-efficient than the average rail transit system. I ran the numbers and concluded that the Volt is more efficient even than BART. Yes, a particular individual who already uses BART would increase rather than decrease total energy consumption by switching to a Volt. But that’s not the point. As a matter of policy, as a matter of which mode of transportation is more energy-efficient in the aggregate, and subject to the qualifiers I have noted, the Volt appears to be vastly more efficient than rail transit.

  • Graham

    The Volt is vastly more efficient than a few low-ridership rail systems. It is perhaps a little more efficient on average than our major legacy heavy rail systems are today – but it not as efficient as these systems would be were they modernized. (Nor is it as efficient as typical electric rail systems overseas.)

    It is good news that the Volt is efficient – electric cars will be an important part of a more energy efficient future (although it will take many years for enough to be on the road to actually have an impact).

    As far as actual trips, it is still vastly less efficient to drive the Volt to work at rush hour than it is to take any form of transit (we have seen that transit can be as efficient as 18 Wh/passenger mile at peak loads). It is also less efficient to drive the Volt long distances than it is to take modern electric high-speed rail (we have seen that HSR averages about 55 Wh/passenger mile). So at a policy level it looks like the recommendation is to move to electric cars for local non-commute trips, modernize our rail transit systems for commuters, stressing energy efficiency, and build efficient intercity high speed rail. I can live with that.

    [I’d like to thank garyg for making me look up all those numbers]

  • Marty Barfowitz

    Graham,

    The Volt is also inefficient because, like all automobiles, it promotes the suburban sprawl — a profoundly costly, inefficient, unhealthy and destructive settlement pattern.

    Rail systems are efficient, in large part, because they promote more centralized, walkable, bikeable, transit-oriented settlement patterns that don’t require cars at all.

  • “He’s talking about the MPG estimate that will appear on the EPA fuel economy label, Nathan. Not the MPG estimate that GM gave last week.”

    In that case, Gary, the one on the label would be even higher. 300 mpg? 500? It’s christmas in trollsville! Except that GM intends for 230 to be the number on the label:

    GM:
    “So in the calculation of the label, for that 230 you take into account the EV distance, the fuel economy after you depleted the charge, and the EPA used a traffic survey that was done in 2001 to create a composite.”
    http://gm-volt.com/2009/08/12/how-the-volts-230-mpg-designation-was-calculated/

    garyg:
    “You seem to have missed this: ‘It was a snapshot in time and based on this dataset…'”

    No. After that double-talk I read through to the reporter’s clarifying question, “How about the petroleum equivalence factor (PEF), is that included?” GM’s answer to that is the one that I’ve already quoted, that the factor is “not included.”

    Hey everybody, if you have any doubts about whether GM’s 230 mpg number accounts for electricity, read that article. It does not. account. for electricity. It is meaningless in a comparison to electrified rail, electric shavers, notebook computers, or anything else that does not burn gasoline. The point is no longer in question among intellectually honest, literate people, so, bye.

  • garyg

    In that case, Gary, the one on the label would be even higher.

    No, it won’t. If the label is as he described, the mpg number on it will only reflect actual gasoline usage, and so will be lower than the 230 mpg estimate from GM (assuming equivalent test procedures, vehicles etc.) The energy used in charge-depleting mode “will get melded in another way and is not included in the MPG estimate.”

    After that double-talk I read through to the reporter’s clarifying question, “How about the petroleum equivalence factor (PEF), is that included?” GM’s answer to that is the one that I’ve already quoted, that the factor is “not included.”

    You’re making mistake as before. He’s talking about the EPA label (“There will be on the label itself…”), not about the GM estimate.

    Again, how do think Nissan could have produced an mpg estimate for the Leaf (367 mpg), which uses no gasoline at all, if the methodology only accounts for actual gasoline usage?

  • Nathan H.

    For what it’s worth, Chevrolet eventually wrote an FAQ confirming in plain words that electricity use is not accounted for the in their 230 miles per gallon figure and that the mileage before the gasoline engage engages is infinite according to their methodology:

    “Q: How many miles per gallon will the Chevy Volt get?
    A: A bit of a trick question. For the first 40 miles it will get infinite mpg, because no gas will be burned. When the generator starts, the car will get an equivalent of up to 50 mpg thereafter. One can calculate the average mpg per for any length drive starting with a full battery: Total MPG = 50xM/(M-40). GM has announced the car will get 230 MPG for the average city driver over time assuming nightly full recharges.”
    http://gm-volt.com/chevy-volt-faqs/

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