Chevy Volt: How It Stacks Up

General Motors has delivered some momentous news this year. There was that inconvenient bankruptcy filing on June 1, and the taxpayer bailout that now totals $51 billion. To get our minds off that, GM recently announced that the Chevrolet Volt, which is now basically a taxpayer-funded science project, will get the equivalent of 230 miles per gallon in city driving. Whoa. In overall driving, GM assures us the Volt will shatter the mythical 100-mpg mark.

There's reason to be skeptical, since GM has overpromised many times before. And if GM ever needed some favorable press, it's now.

But so far the Volt is standing up to scrutiny, and the closer we get to the scheduled launch late next year, the more innovative the Volt appears. Even though most Americans won't buy one, the Volt could create one of the first meaningful alternatives to gas-powered cars. It could also change the way we think about fuel economy—and reinvigorate beleaguered GM.

The Volt isn't a hybrid like the Toyota (TM) Prius or Honda (HMC) Insight, which rely on a battery pack to assist the gas engine that powers the car. The Volt is designed to run on battery power alone for up to 40 miles, with drivers able to recharge it through an ordinary electrical outlet. Once the battery runs low, a 4-cylinder engine will automatically start up to power a generator that will power the wheels. The reason the Volt could get the equivalent of 230 miles per gallon is that on many short trips, the gas engine wouldn't even be on.

I'm usually suspicious of impressive-sounding numbers, so I interviewed Tony Posawatz, who runs the Volt program for GM, to find out what the catch might be. The 230 figure isn't an official government number, as GM has readily acknowledged. The Environmental Protection Agency, arbiter of official fuel-economy figures, hasn't yet settled on a final method for measuring fuel economy for cars like the Volt that run on more than one type of fuel, with efficiency dependent on the length of the trip.

Without providing an exact methodology, Posawatz explained some of the assumptions backing the 230-mpg figure: Drivers get just one charge, and most drive less than 40 miles on their city voyage, which is consistent with government data showing that most Americans drive less than 40 miles per day. Those people are "infinity drivers" who would literally burn no gas, ever, if they drove the Volt less than 40 miles every day (and they remembered to plug it in every day when they got home, and the Volt worked perfectly, and the car wasn't packed with weight-lifting equipment, and . . .). Some other drivers in GM's city profile presumably drive more than 40 miles or are horribly inefficient drivers and burn gas. That would lower the Volt's city gas mileage from infinity to 230 mpg, or the equivalent.

Highway mileage, Posawatz admits, will be lower. But overall, he says, "it will be better than any conventional car out there." That means the Volt would handily beat the Prius, which gets a combined 50 mpg and is the reigning gas-mileage champ among ordinary production cars. That alone would be a victory for GM.

But forget mpg. That's so 1990s. The EPA prefers to measure the efficiency of electric plug-ins in terms of kilowatt hours per 100 miles traveled. GM says the Volt's optimal performance will be about 25 kWh/100 miles. Boy, that sounds efficient, doesn't it?

Actually, who knows? So forget kilowatt hours, too. The Volt and other energy breakthroughs will probably force us to become more conversant in electrospeak, but for now there's a simpler way to compare the efficiency of the Volt to just about every other car: Cost per mile. "That's the all-in," says Posawatz. The beauty of this metric is that anybody can calculate comparisons, with info that's generally available, in terms we all understand.

GM says that 100 miles of battery-powered travel in the Volt will require about $2.75 worth of electricity. That's based on typical electricity rates of about 11 cents per kWh. (Check your electric bill to find out how much you pay.) That amounts to 2.75 cents per mile. If drivers charge their Volt overnight, when off-peak electricity rates are much lower, the cost could be as little as 1 cent per mile, according to Posawatz.

GM hasn't said what kind of "mileage" the Volt will get when it's running on the 4-cylinder engine, but somebody who regularly depleted the battery and kept on driving might pay 4 cents per mile or more, after factoring in the cost of gas. (Of course, it's possible that a Volt owner might never charge the battery and always drive on gas, which would be foolish but not that much different from an individual who buys a big, off-road SUV and rarely drives more than a few miles from home.) Overall, Posawatz suggests that 2.5 cents per mile might be a good comparison figure.

Let's assume he's overstating the Volt's efficiency, and use 4 cents per mile. How does that compare to my Mazda 3? Here's the math: The version of the 3 I own averages 25 mpg. Gas currently costs $2.62 per gallon where I live, so it costs me $10.48 to drive 100 miles. If I divide by 100, I get a cost per mile of about 10.5 cents.

Hmmm. That doesn't seem so good compared with the Volt, and the 3 is pretty thrifty. If gas spiked to $4 a gallon again—which many energy analysts think is quite possible, by the way—my Mazda would average about 16 cents per mile. The Volt, meanwhile, would probably still cost 4 cents per mile or less, since electricity prices tend to be more stable than gas prices.

For other popular cars, the comparison is worse. A four-wheel-drive Toyota Highlander, for example, averages 19 mpg, which means the gas required to go 100 miles costs about $14, at $2.62 per gallon. That equates to 14 cents per mile. With $4-a-gallon gas, it would be 21 cents per mile. At the other end of the spectrum, fueling the Prius costs a little over 5 cents per mile at $2.62, and 8 cents per mile at $4.

Anybody can play with these numbers, and even customize them for their own region, for both the Volt and the family car. Gas prices for various regions and some states are here. The Department of Energy breaks down average electricity costs by state at this Web site, for people who want to plug in local prices to determine the Volt's potential charging costs where they live. For now, we're dependent on GM's claim that the Volt uses about 25 kWh of electricity to go 100 miles. So people doing their own calculations need to figure out how much 25 kWh of electricity would cost, then divide by 100 to get the cost per mile. GM does appear to be playing it straight in terms of the gas and electricity prices it's using.

There are a lot of other factors that will ultimately determine whether the Volt is worth the expected sticker price of about $40,000 and whether it actually cuts fossil-fuel use when the entire "well-to-wheel" costs, in terms of both dollars and pollution, are calculated. The cost-per-mile figures I've been fiddling with are for fuel only. Maintenance, repairs and other factors could end up costing more on the Volt than on other cars. Or the Volt's huge battery might not be able to deliver a full 40-mile driving range over its entire lifespan in real-world conditions.

The Volt's higher price could also outweigh any gain in fuel efficiency, although government rebates will probably bring the cost down by several thousand dollars. Still, the Volt is a first-of-a-kind product, which means the technology costs aren't expected to be recouped right away. And so far, GM appears to be delivering on its promises. One of those promises is to deliver a game-changing vehicle. If the Volt catches on, we could start to see window stickers and official government Web calculators that help consumers compare the cost-per-mile of various vehicles, no matter what fuel they run on. That could start the fade-out of mpg, which sounds like a new game to me. And a pretty exciting one, too.

Disclosure: no positions

Comments

[car_guy:]

Rick,

Good article. Accurate and factual and objective. Rather rare traits for Auto articles on Seeking Alpha. I strongly agree with the thesis that cost/mile is a superior rating to mpg for consumers to use. This should be one of a number of possible metrics for rating performance/efficiency based on a person's objectives/expectations. A web calculator for carbon/mile would be straight forward to develop based on the location of the user. A calculator for petroleum used/mile would also be useful if we are still interested in reducing dependence on foreign oil.

Aug 23 12:59 PM

[manya05:]

How to compare apples and apples, easy problem, the Europeans have already solved it. Forget the mpg, you rate cars based on the grams of CO2 emitted per km traveled. In the case of full-electric cars you would use the CO2 emitted using the "average generating mix" of the US utilities to produce and transport that kWh that ends up in your battery (the fuel tank). So it would be easy to compare the Volt against any car, it will look better I am sure, but not that much better (another case of false advertising).

Further, as done in many places, the government could establish targets for the g/km of CO2 emitted for each "class" of car (based on weight for instance). Then, if your model exceeds that target you get a bonus proportional to how much better than the target you are, while if you are below the target you get a malus. The money for the bonus comes from the malus extracted from the below-average cars. In other words, you force the less efficient cars to subsidize a lower price for the more efficient cars. Accelerated darwinism, the companies that cannot innovate and up the fuel efficiency will end up paying the good companies to accelerate their R&D and get even better. Eventually the bad companies will go out of business, and those that can get the best numbers (lowest) of g/km of CO2 emitted will rule the land. Such system will really get the ideas flowing (and possibly break the logjam and allow smaller car companies with really innovative ideas to gain market share).

Aug 23 01:29 PM

[Gandalph:]

Do the efficiency numbers! The efficiency of a power plant - coal, oil, or nuclear is about 40%; the efficiency of the grid is estimated at 92%; the efficiency of charging a Li-Ion battery is no more than 85% (They get hot!); the efficiency of an electric motor is about 85%(They also get hot); call the AC to DC converters 85% (?). Overall: 22.5%. Compare with modern clean diesel: ~48%. If you live where you get cheap subsidized electricity, you have the allusion of high "mileage," but society (We) collectively pay the bill. It looks like "oil" made from algae is going to work, making this debate meaningless.

Aug 23 02:56 PM

[User 283977:]

Understanding the math behind the claim helps. Based on this link, (www.thestar.com/busine...) it appears the MPG claim is based on the following logic:

If you drive 50 miles, 10 miles are augmented by running the internal combustion engine (i.c.e.) that gets 50 MPG. So those 10 miles consume .2 gallons of fuel over the total 50 miles. So you are getting 50 / .2 = 250 MPG. Multiplying by .92, you get 230 MPG. The .92 is an adjustment for energy consumed by the battery.... Some kind of an efficiency factor.

Here are average miles per gallon numbers for different average miles per year, assuming the i.c.e. gets 50 miles per gallon, and the E-Range is 40 miles.

Av miles per year Adj Miles / Gal
15000 1725.00
17500 277.59
18250 230.00
20000 170.37
22500 131.01
25000 110.58
27500 98.06
30000 89.61

So the 230 MPG figure is specific to the average number of miles driven per day, the MPG of the i.c.e., AND the E-Range. If charging was available where the vehicles were parked, that effectively extends the E-Range.

Aug 23 03:23 PM

[TCK:]

Instead of MPG seems like TCO ( Total Cost of Ownership ) should be the new model. Will the Volt run 100 K miles or 60 K. That is still an unknown. How long does the battery in your notebook computer last ?

Also don't forget to add the $20 Billion bailout of GM/UAW to the cost of the vehicle !

Aug 23 04:06 PM

[User 283977:]

Yes, I like the total cost of ownership approach, but won't it vary as a function of miles driven?

Aug 23 05:10 PM

[Longinvestor:]

"The EPA prefers to measure the efficiency of electric plug-ins in terms of kilowatt hours per 100 miles traveled. GM says the Volt's optimal performance will be about 25 kWh/100 miles. Boy, that sounds efficient, doesn't it?" Rick Newman.

Let's say you never plug the car into the grid, but just use gasoline only, like you would need to do on a long wilderness fishing trip.

Just as a sanity check, an off the shelf portable Honda electric generator rated at 6500w can do this:
6.5kW * 14hours / 4.5 gal-gas = 20.2 kWh / gal-gas
1.24 gal-gas = 25 kWh

100 mi / 25 kWh = 100 mi / charge per the above article.

25 kWh (from a Honda generator) = 1.24 gal-gas

100 mi / 1.24 gal-gas = 80.6 mpg on gas only

Of course you don't need the Honda electric generator because the Volt has its own gas powered electric generator on board.

Aug 23 07:26 PM

[TinyTim:]

More smoke and mirrors on hybrid vehicles, which includes the series hybrid Volt.
As some commenters have alluded to, for a plug-in hybrid, mpg can be anything depending on the driving cycle because of the ability to run electric only with external recharge.

"simpler way to compare the efficiency of the Volt to just about every other car: Cost per mile....The beauty of this metric is that anybody can calculate comparisons"
Yeah, if they're an engineer and / or good with math. Like an EPA appliance sticker, there are a lot of variables at work that are assumed.

The easy comparison is pure gas or pure electric:
100 miles at 30mpg at $3.00/gall = $10.00
100 miles at 25kWh at $0.06/kWh (off peak) = $1.50
For a non-plug-in hybrid, the comparison is still mpg because all the energy is gasoline derived.

As soon as plug-in capability is added to a hybrid (sometimes referred to as extended range), the car can run external electric only and the only two specs that will provide a consumer with anything meaningful are the electric range and the hybrid mpg; both for city and highway cycles (four numbers). Based on these specs, if he knows his cost of gas & electric, plus his typical driving cycle, and has a math major handy, he can estimate his cost per mile. Anything else is pure BS.

Since these plug-in hybrids are referred to as extended range, ironically because they still have the gas engine for when the batteries run down (GM is jumping the gun a little on their "electric cars"), it's interesting to guestimate the mpg when the batteries are run down.

The simplest approach is on a flat highway at constant speed with no extra engine power draw used to recharge the batteries. Mr Peterson's Economist article estimates 20mpg for the Volt 1.4L engine.
Toyota has optimized this for the Prius and gets 50mpg.
A comparable regular 1.5L Toyota Yaris or an older 1.5L Honda Civic both get around 38mpg highway. Unfortunately, the series hybrid Volt has to change the gasoline energy to electricity, then back to mechanical motion, both inefficient conversions. On the other hand, like the Prius, the engine in the Volt can be optimized for single speed operation in the mpg sweet spot in this highway situation.
My guess is 40mpg-highway engine-only for the Volt.
It won't beat the parallel hybrid Prius.
No GM victory on the highway.
No advantage as a highway cruiser over a non-hybrid, that's for sure.

One thing the Volt has going for it is the simplicity and lower cost of the series hybrid drive train over a car like the Prius. This should make it easier to improve the reliability, a competitive issue for GM. Also, maintenance and engine life should be better. Like a laptop computer, the batteries can be swapped out as newer improved technologies come along for longer electric range. I wouldn't be surprised to see other new hybrids adopting the Volt series hybrid format, like the newly announced Toyota Vitz / Yaris hybrid.

Aug 23 09:06 PM

[jbde:]

you said:

"The reason the Volt could get the equivalent of 230 miles per gallon is that on many short trips, the gas engine wouldn't even be on."

if the engine is not on, the mpg would be infinite ..... but;

Before you jump on me, to determine the MPG of an EREV; first the car is driven from a full battery until it reaches charge-sustaining mode [engine on], then one more cycle is driven. If we use the highway schedule first from a full charge, the first 40 miles are electric covering the hiway course of 10.26 miles and continuing until the engine comes on to ready for the city course of 11.04 miles. If the Volt gets 50 MPG in charge sustaining mode, it will use .22 gallons of gas for that 11 miles. Thus 51 miles/.22 gallons = 231.8 MPG. Close to the GM quoted figure of 230mpg.

The real issue comes from Einstein - E=mc^2

Since there is no transmission, there is alway a direct relation to speed squared. Thus to sustain a faster speed over a given distance requires more energy [than if you covered it at a lower speed]. This is why the Volt is not good for long high speed trips. The real question is how fast you can go in charge sustaining mode, or even in charge draining mode - both with the engine running. Then produce a table for distances at various speeds so you can determine when you will be stranded.

What if you drain the battery below sustaining charge levels and continue to dirve? Of course you should be able to "idle" and recharge the battery as opposed to plugging it in - but that is real bad mpg! Like - zero.

Aug 24 07:59 AM

[simpsonj:]

no matter your point of view on volt mpg, how interesting for GM to have the world talking about what level of 3-figure mpg the volt will get instead of talking about bankruptcy or running our of money or poor product decisions or loss of marketshare. That really is an accomplishment.

Aug 24 11:42 AM

[Pro Hac Cev...:]

The Volt is an EPIC FAIL.

www.youtube.com/watch?...

Aug 27 12:07 PM

[driftwood2:]

Personally, I don't think the first versions of these products are going to be big sellers. They're trailblazer products that will be the future of automaking. Electric vehicles will need a better battery to be viable. Lithium phosphate will deliver that I believe and it is waiting in the wings. A little more development and it will be ready for prime time. It's already used in some fancy power tools.

Aug 27 12:13 PM

[User 377624:]

It's c

Aug 27 01:48 PM

[Forever Bear:]

Soon other automakers will come up with their own version of plug-in hybrid, use GM's method to calculate MPG and beat their number.
GM should be honest about Volt's estimated top speed and other performance related data. Running on battery alone at freeway speed, you will need a great deal of power and the technology is expensive.
The original Volt design was ground-breaking, and I was disappointed with the current design. Somehow I don't foresee people flocking to their nearest GM dealers when Volt becomes available.

Aug 27 01:58 PM

[User 377624:]

Why is Chevy is including the driving while fuel is not being used into it's miles-per-gallon calculation? That gives us a completely useless figure.
My car can get 1000 miles per gallon if I push it for a while and then use the engine. Hey, I could even get 5000 mpg by pushing it 5 times farther or by using the engine for 1/5th as long.
The useful numbers are mpg while using only fuel, and miles per kwh while using only electricity. The only way to combine these to one number is to do what the author did here, dollars per gallon, or $pg.

Aug 27 01:59 PM

[Steve0:]

GM is going to follow the Volt with a similar powered Cadillac which looks just awesome. I plan on having one of these in my driveway and thumbing my nose at the foreign auto manufactures and middle east oil!

Aug 27 02:46 PM

[dw57:]

you forgot to add the efficiency of the tankers shipping the oil, the refineries, and the oil fields, finding said oil fields, and can't forget drilling in deep water or adverse climates. If you going to include the collateral electrical production efficiency you need to include all of it.

On Aug 23 02:56 PM Gandalph wrote:

> Do the efficiency numbers! The efficiency of a power plant - coal,
> oil, or nuclear is about 40%; the efficiency of the grid is estimated
> at 92%; the efficiency of charging a Li-Ion battery is no more than
> 85% (They get hot!); the efficiency of an electric motor is about
> 85%(They also get hot); call the AC to DC converters 85% (?). Overall:
> 22.5%. Compare with modern clean diesel: ~48%. If you live where
> you get cheap subsidized electricity, you have the allusion of high
> "mileage," but society (We) collectively pay the bill. It looks
> like "oil" made from algae is going to work, making this debate meaningless.

Aug 27 03:42 PM

[dw57:]

the government didn't fund the Volt until after the bankruptcy. this project started last year long before the government ever was involved. and a lot of the design was inspired by GM's trains. They have been series hybrids for decades now. and for a demonstrator vehicle its pretty cheap (compare it to the Honda hydrogen powered car). and even the Prius was a loss for Toyota when it first came out. and if it works any where as well as they think it might (i seem to recall that +200 mpg was an up to sort of thing). and most gas and oil powered cars don't do that well in town, the up 20 mpg in town works unless you are in stop and go traffic, in which case you are not likely to even come close

On Aug 23 09:32 AM jerrydd wrote:

> In general a great article!!
>
> The best rating would be 2, 1 the mileage using only power supplied
> by the engine and another with just plug in power. That way the owner
> can figure out what it will cost them.
>
> While I expect late next yr gas will be $4/gal even then even if
> you get 1000mpg at $40k it isn't going to be worth it on economic
> grounds.
>
> The facts are GM has paid nothing to design, build the Volt as the
> gov has paid it all in grants, as has the other US companies on their
> Plug in hybrids, EV's, so they have no excuse other than keeping
> the Volt from being cost effective.
>
> Their big mistake is not using a much smaller engine around 35hp
> and not connecting it by clutch for freeway driving. Then the motor
> and it's 25kw generator/motor both could help the main EV motor if
> more power is needed.
>
> Adding to this lower weight is well worth it because for every 3
> pounds removed, a lb of battery and another of engine, EV drive could
> be dropped, nicely lowering the overall costs.
>
> As a custom EV builder, daily driver 250wthr/mile GM states sounds
> about right. However in a composite EV like the GM UltraLite show
> car from decades ago done in medium tech composites instead of carbon
> fiber could only need 100wthrs/mile so with the same battery pack
> get 130 mile range!!
>
> It's not like GM doesn't know about this as their Impact EV, the
> EV-1 pre-prototype did exactly this. An Impact or UltraLite could
> be built for $25k and with the battery tax credit of $7500, be a
> real bargain and seller that is cost effective.

Aug 27 03:48 PM

[dw57:]

they do that because that hows the EPA has dealt with hybrids (which can on occasion run on battery only).
the $ per mile sounds pretty good, and even is probably pretty close to what MPG was intended to do. and the cost per mile would include every thing to produce your energy source (in theory any way).


On Aug 27 01:59 PM User 377624 wrote:

> Why is Chevy is including the driving while fuel is not being used
> into it's miles-per-gallon calculation? That gives us a completely
> useless figure.
> My car can get 1000 miles per gallon if I push it for a while and
> then use the engine. Hey, I could even get 5000 mpg by pushing it
> 5 times farther or by using the engine for 1/5th as long.
> The useful numbers are mpg while using only fuel, and miles per kwh
> while using only electricity. The only way to combine these to one
> number is to do what the author did here, dollars per gallon, or
> $pg.

Aug 27 03:50 PM

[dw57:]

well GM's trains have been using series hybrids for decades. seems to have worked really well for them. and as some noted the drive train is really simple compared to a regular hybrid. there is only really one motor/engine and thats the electric one. the other is really a glorified generator. and electric motors are really simple, we have been building them longer than gas/oil engines. and they have been shown to last a long time. the fly is the battery. but we have been building batteries a long time to, just not ones this big. but they are simple and easy to replace too


On Aug 23 04:06 PM TCK wrote:

> Instead of MPG seems like TCO ( Total Cost of Ownership ) should
> be the new model. Will the Volt run 100 K miles or 60 K. That is
> still an unknown. How long does the battery in your notebook computer
> last ?
>
> Also don't forget to add the $20 Billion bailout of GM/UAW to the
> cost of the vehicle !

Aug 27 03:58 PM