Filed under: EV/Plug-in, Hybrid, Chevrolet, GM
EPA vs the Chevy Volt: Hybrid or electric car? 48mpg or 100mpg?
The Chevrolet Volt raises a lot of questions. From its public unveiling in January 2007 people wondered, is it a hybrid or an electric car? Right from day 1 in December 2006 before the auto show, GM officials have called it a range extended electric car. They use the electric car terminology because, unlike what we think of as hybrids today, only an electric motor drives the Volt. The engine, a normally aspirated 1.4L (not turbocharged as Motor Trend indicates) just drives a generator (not a two mode hybrid unit as MT says) instead of the wheels. However, the presence of the range extender causes the EPA to consider it a hybrid and they expect it to have almost a full charge at the end of the test cycle. The design intent is that the battery would be run down after having run more than its 40 mile electric range during the test. As designed, the engine would only run 15 percent of the time during the current EPA cycle and would yield over 100 mpg. But, using the EPA's methodology and having the engine keep the battery near full charge - which completely defeats the purpose of a plug-in vehicle with a 40 mile electric range - the Volt would only get about 48 mpg. While not a bad number, it's no where near reflective of what the Volt could achieve in the real world for most drivers. Clearly the EPA needs to work with manufacturers to change the testing methodology and come up with something that more closely approximates real world conditions for plug-in vehicles. Insisting on something else would force automakers to calibrate plug-ins to meet those requirements at the expense of real world efficiency, helping no one.
Gallery: Chevy Volt Concept
[Source: Motor Trend]
Reader Comments (Page 1 of 2)
tankd0g 8:58PM (9/06/2008)
I think in the case of this car they should do the test twice, once with a full charged battery and once with a flat (well as flat as the computers allow it to get) battery. Those are the only two numbers I'm interested in.
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AMcA 7:08PM (9/07/2008)
Yeah, but how far are you going to drive it during the test? Go a few feet past 40 miles, your mileage will be near infinity. Drive 10,000 miles without a charge-up, it's going to 50ish.
The Volt just doesn't fit the usual EPA model at all.
meme 10:11PM (9/06/2008)
It's *NOT* a 100 mpg car. It's a 48mpg car with a 40 mile all-electric range. You cannot represent what a PHEV does with one number. The EPA number is just fine; it simply needs to be displayed with the electric range. For example:
"40 miles electric, then 48 mpg"
Not particularly challenging. I've seen a more concise, but more cryptic, terminology, as:
"48mpg PHEV40".
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Redvette 11:36AM (9/07/2008)
That is a good way to provide all the information necessary. Like a lot of us, my daily driving is under 40 miles. If I go on a long road trip, I will probably use another all-gasoline powered vehicle anyway.
Snowdog 10:11PM (9/06/2008)
Clearly the EPA is doing the right thing, they need to stick to their guns on this one. The battery charge should not be counted in the mpg measurement (have we started selling electricity by the gallon?).
I have been saying all along that this kind of measurement is completely pointless and they number that comes out of it is completely arbitrary. It is NOT a helpful or usable number. The numbers that will actually help people are the battery range and the mpg after the battery is exhausted.
It is the same with the Aptera bogus 300mpg claim. Put a gallon of gas in an Aptera and fully charge and it still won't go 300 miles because in their fudged calculation they are including multiple charger per gallon of gas to get the made up number. This kind of crap does nothing for the consumer it is just a way to hype a pumped up number.
What number is important if I go an a road trip. The hyped/over inflated one or the real charge sustaining MPG.
40 mile electric range and 48mpg tells you everything you need to know in an honest fashion.
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Chris M 12:45AM (9/07/2008)
While I agree that some of the figures that have been extolled by plug-in proponents are highly misleading, I'd also say the EPA was being bureaucratic and obtuse. It makes no sense to insist that a plug-in vehicle be modified to operate in a non-standard manner. Forcing the range extender to fully recharge the battery would never happen in normal operation, and would result in abnormally low fuel economy readings
I'm not prone to conspiracy theories, but I get the sneaky suspicion that some Bush jr. appointee in the EPA may be deliberately trying to sabotage plug-in hybrid projects to benefit the oil companies.
SteveCT 1:37PM (9/07/2008)
To be fair to Aptera, their car IS extremely efficient. They do fudge the numbers with that crazy 300 MPG claim, but the fact is that the car gets 130 MPG even when the battery is drained. Which is a lot better than the Volt, albeit with one less wheel and fewer seats.
I'm with Meme. Give the MPG when the battery is drained, give the all-electric range, give the WH/mile, and there's your data set. That's everything the consumer needs to know, with no BS.
I do disagree with the EPA's absurd insistence that the battery be kept at full charge. Why not just drain it to the 50% they designed it to drop to, and then test the MPG? It's essentially the same test, and it doesn't require the vehicle to be altered just for the test, which makes the entire test suspect. But of course we'll have to wait until the current bozos are out of the White House before we can expect any sanity from the executive branch.
Phil L. 10:13PM (9/06/2008)
This merely reflects the nature of regulatory agencies: they follow technology; they don't lead.
As new developments are released, the EPA will have to update their methods to properly assess it.
Meanwhile, knowledgeable consumers understand the limitations of government, and will instantly see the value of this new drivetrain. They will also note the deficiencies of the EPA's measurements, and bitterly complain about it. Hopefully, change will come sooner rather than later.
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ziv 11:03PM (9/06/2008)
But to call the Volt a 48mpg car is ludicrous! Most people won't use more than 5 or 6 gallons of gas a month at 1200 miles of driving. Almost all of my driving is done at the rate of about 20-30 miles per day. I won't use any gasoline most days. About once a month I go on a road trip and drive 200 miles. Then I will use 3 or 4 gallons, but the range extender will seldom be used otherwise. And that is how most people drive. We drive 12,000 miles a year, maybe 15,000 miles at most. And 15k miles a year is 41 miles a day. When you take the monthly road trip out of that the Volt doesn't use any gas for weeks at a time.
We need to be independent of foreign oil, and having the EPA discouraging EREV tech is helping our enemies in Venezuela, Iran, Russia and Saudi Arabia. Do this logically, but don't let the bureaucrats damage our conversion to electric cars.
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SteveCT 1:42PM (9/07/2008)
All of that is true, ziv, but the fact is that the EPA needs to be objective in testing vehicle MPG. All those things you said are things that dealerships can and should tell consumers to sell them the car, but the EPA should just give the hard data and nothing else. There's got to be a number, and when the battery is drained, the MPG is 48, apparently. That's what people will understand, so that's what the EPA should do. Let the dealer explain the advantages of having an all-electric range; it's not the EPA's job to do so.
indi 11:31PM (9/06/2008)
The Volt is a hybrid, not a pure electric car. The Prius is a parallel hybrid, the Volt is a series hybrid. I'd really expect autobloggreen to know this stuff...
So whether the Volt is a 48 MPG car or a 100 MPG car depends entirely on how much your average daily range is. The EPA is correct in their classification, but they will probably need a new method for estimating the mileage for series (and perhaps also plugin) hybrids. Perhaps a tiered rating which shows several MPG figures according to how much daily driving the owner will do.
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kery beauhrt 12:05AM (9/07/2008)
Confirmation that the EPA is manned by brainless morons.
Their own commuter trip stats clearly prove a car like the Volt would achieve over 250 MPG while commuting, which accounts for fully half our gas usage. And that's not allowing
for any workplace recharging, which is totally absurd. My estimate is tha the Volt will achive at least 250 MPG overall and that it could easily top 400 MPG with a few reasonable assumptions. This isn't rocket science, EPA folks. Look at you own statisitcs and stop trying to apply inappropriate mileage test loop results - they are totally meaningless when dealing with plug-in hybirds. Jeeez!!!! That's our tax dollars in action.
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Snowdog 7:55AM (9/07/2008)
Here lies the complete absurdity of your position (and many others here) and the Justification for calling this car exactly what it is. An electric car with 40 mile range and 48mpg range extender. That is all anyone needs to know to figure out how it will work for them and their usage pattern.
You quote numbers from 250mpg to 400mpg. These are completely meaningless and arbitrary. This should highlight cleanly the utter foolishness of trying to use such loaded arbitrary numbers for the rating of this vehicle. This tell you nothing!
Hey why stop there? In the last 2 months I only had one day trip over 40 miles. I estimate by these hair brained methods my MPG would be 2000mile/.25Gallon = 8000mpg.
There we go. 8000mpg. That's what the EPA should say.
Getting a clue yet what the problem with this is? Probably not.
If I tell you it gets 100mpg or 250mpg-400mpg like you claim or 8000mpg like the above. They are all arbitrary, meaningless numbers, that don't tell anyone anything.
It is an electric car with a range extender. It gets 40 miles electric range first, then 48mpg on the extender after that. These numbers tell you everything you need to know and are accurate and honest.
Red 9:15AM (9/08/2008)
@ Snowdog,
GM's own estimates put the range extender calculation at hundreds of miles driven the way it's built. Not arguing with you, but it's unrealistic to test the vehicle in a way consumers would more than likely never drive it. At least, that is my understanding of what the controversy is.
The problem isn't so much, "hey, the EPA said I would get lower than I'm getting" (when's the last time that DIDN'T happen?). I think the problem, aside from GM's marketing department having a cat-turd fit, is misleading people from thinking this vehicle isn't worth the $40,000 price tag (that's completely up to the end user to decide). It'll also redirect a large number of potential Volt customers toward Toyota's dealerships even though the Volt is nothing like the Prius. Most consumers are ignorant. They see the mpg, they see the dollar amount and make a large percentage of their choice based on that. That's the current trend with Prius sales. There are vehicles that make more sense than the Prius, but chalk one up to Toyota's marketing for taking advantage of folks. Again.
I still think Lutz should've kept somewhat hush on this one and let fuel cells, two-mode hybrids and other GM tech take the spotlight until at least the Volt was proven beyond concept form. As it stands, everything--and perhaps even, everyone--seems to be working against it, starting with Lutz' big mouth.
Joseph 12:09AM (9/07/2008)
The solution is very simple. The EPA rated an EV's mpg by mpg equivilant. Do the same for cars like the Volt; you just need to add the gallons of gasoline used to the "gallons" of gasoline equivilant used.
So, the Volt uses something like 10 kwh for a 40 mile journey. Since a gallon of gasoline holds the equivilant to about 33kwh, that means the Volt used about a third of a "gallon" to travel forty miles.
That means it gets around 120 miles per "gallon."
Now, (according to the information provided in this blog post) the EPA test is 46 miles, leaving 6 miles not in EV mode.
Let's suppose that the car gets 50mpg in this mode. That would mean that 85% of the test is 120mpg and 15% of the test is 50mpg.
For the first forty miles you would use 1/3 a gallon of "gasoline" and .12 gallons of actual gasoline for the remaining six miles. So....forty six miles and .45 gallons of gas.
That comes up to the grand total of 102 miles per gallons equivilant.
So, assuming my math is correct, the EPA rating for the Volt (in my opinion) should look something like this:
FULLY CHARGED
City: xxx mpg equivilant
Highway: xxx mpg equivilant
Combined: 102 mpg equivilant
EMPTY/HYBRID MODE
City: xx mpg
Highway: xx mpg
Combined: 48 mpg
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Glenn 3:32PM (9/07/2008)
Well put. This is probably as close you're going to get to a electricity vs. gasoline comparison.
It would also be the way to calculate an electric only vehicle as well as a hydrogen fuel cell car.
Chris M 12:20AM (9/07/2008)
Sounds like GM should contact their Representatives and Senators and request a bill be put before Congress to order the EPA to devise proper testing procedures for plug-in hybrids and other vehicles that are fueled by more than one type of fuel (BMW Hydrogen 7 comes to mind). If GM doesn't do it, maybe we will have to!
The testing should determine the efficiency and driving range of each type of fuel. In the case of plug-in hybrids like the Volt, they would determine the electric only range and the miles per Kwh, then determine the gas fueled range and the miles per gallon while using gas.
The real complication comes when the two fuels are effectively blended and used at the same time, that would apply to the "compressed air and liquid fuel" hybrid that Guy Negre is proposing, and it might be the case for some plug-in hybrids as well. In that case, it would be necessary to list a "combined fuel range", and the total amounts of both fuels used to achieve that range.
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Geoffrey de Ruiter 12:48AM (9/07/2008)
The best option is to continue what I have seen been done in the past. Now I happen to believe that recently fueleconomy.gov changed what they had on electric cars to MPG as the old Rav4 EV now says eMPG (http://www.fueleconomy.gov/feg/noframes/17328.shtml), however, what I saw at some one point was Watt.hours/Mile for electric. This would be universally recognizable in all parts of the world because everyone uses watt.hours for a volume of energy (just like a gallon of fuel). Yes I know miles and km would still be different but you can only do so much. So in the end you still have the Highway and City for electric mode (as would be shared by all EV, extended range or not), and then the Highway and City for hybrid mode just like every other vehicle on the road today. With a nice little table (Highway and City on the top, and Electric mode and Hybrid mode on the side) you have a simple view of everything you need. Then add in the electric mode range under the table.
!The problem with eMPG is that no area is 100% coal/oil/nat gas for power production and thus there is a highly variable mix, and what do you say about people with solar panels or that live off grid? Ugh my brain starts to hurt thinking about that and it doesn't even have pain nerves!
Go with the Watt.hours/mile or miles/Watt.hour (or replace miles with km for the metrics) and your done. There will always be online converters for the keeners that want to know the eMPG. The US and UK needs a new system anyway, it won't take people that long to see the ranges when shopping around, e.g. Aptera VS Yukon series hybrid (if it ever existed)
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why not the LS2LS7? 2:05AM (9/07/2008)
Watt-Hours are not more "rest of the world" than gallons of gas. Both are colloquial units.
Joules are the SI figure for a volume of energy. A Watt-hour is 3600 Joules, BTW.
Geoffrey de Ruiter 1:41PM (9/07/2008)
Not you again LS2LS7! you always respond in the same way, give it up. Thanks for the 12th grade update on Joules being like watt-hours because I wouldn't have known that before writing the post, industry doesn't use Joules (as much as I like the SI system), science uses joules when analyzing work and energy, but electrical systems use watt-hours. Now of course there is cross over, but the system for EV was already set up with watt-hours back in the late 90s and it was a good system and that is what I was trying to describe. So question to you LS2blah, tell me another unit of electrical energy that another part of the world uses, and tell me the proportion of the world that uses it. I'm pretty sure watt-hours are adopted uniformly. But hey I could be wrong. I've spent too much time responding to you.