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Richard230
25 November 2010, 1242
The numbers go round and round. In an article titled "Electric Volt will get up to 93 mpg" written by Tom Krisher of the AP, it states that the Chevy Volt will get the equivalent of 93 miles per gallon of gasoline, according to Chevrolet. The claim is that when the IC motor is running it will get 37 mpg and in a drive cycle that combines both battery power and generator power, it will get 60 mpg. These figures are estimates from the US EPA and will appear on the Volt's window sticker. The article notes that GM had originally estimated that the car would get the equivalent of 230 mpg in city driving according to their calculations. In the Volt's full-electric mode, it is expected to get the equivalent of 95 mpg in the city and 90 mpg on the highway, according to EPA estimates. Running on only the IC generator, the car is expected to get 35 mpg in the city and 40 mpg on the highway.

The article says that Nissan said earlier this week that the Leaf would achieve the equivalent of 106 mpg in city driving and 92 mpg on the highway.

The article goes on to say that the Volt takes 12.9 kWh to recharge the car at 240 volts (doesn't it take the same amount of energy to charge at 120V?). The calculation is based on a formula that equates 33.7 kWh to the use of one gallon of gasoline. This is highlighted for those of you that want to race IC motorcycles against electric motorcycles and are looking to establish some rules for your new racing association.

So I am really confused about these numbers. It seems like mpg figures for EVs and the like are tossed around by manufacturers by throwing darts at a dartboard full of mpg numbers to see what sticks with the government. I am looking forward to the public buying these vehicles and then hearing what they tell reporters the sort of mileage that they actually get - or think they get. I'll bet the method of figuring "mpg" by the government will change once they get public real world "feedback".

And don't forget public perception is 99% of reality in the US. :rolleyes:

Skeezmour
25 November 2010, 1304
Thanks for posting this Richard. When I started toying around with the calculations I used the high range for stored energy in a gallon of gas. Reality is it all depends on blend, time of year, temprature ect. My figures were 1 gallon gas = ~36.6kwh.

I helped put almost 10k miles on a Rav4 ev conversion and we consistantly got 80-95 miles without running it out of juice. Most of that was at full freeway speed and not trying to drive nicely. Pack size was 30.7kwh nominal. So by there numbers a car that gets sub 330wh/mile (calculated at the wall) is over 100mpge.

DaveAK
25 November 2010, 1315
Does the kWh to gallon of gas comparison take into account efficiency of converting the potential energy to kinetic? What's the basis of comparison? Cost to the consumer or something else?

Skeezmour
25 November 2010, 1421
That is simply a conversion of the stored energy from one metric to another. There is nothing about how effiently they use it.

DaveAK
25 November 2010, 1436
That is simply a conversion of the stored energy from one metric to another. There is nothing about how effiently they use it.
OK, so that makes sense. For 33.7kWh you could go maybe 100 miles, and on one gallon of gas you might go 30 miles.

Skeezmour
25 November 2010, 2201
OK, so that makes sense. For 33.7kWh you could go maybe 100 miles, and on one gallon of gas you might go 30 miles.

Right on the money. One of our Rav4 conversions could go close to 100 miles with 30.7kwh on board at freeway speeds with roof rack and a spare tire in the back. We live in a fairly rolling hill area so that same car at its new home witch is flatter can do 120+ miles. I'm sure part of it is we didn't try and drive nice with it.

So comparied to the Rav 4 when it still had a fuel milage average of maybe 29-30mpg it was over 3x more efficent. Oh and it was pretty darn cold here when we were putting all those miles on that car.

DaveAK
25 November 2010, 2328
Where do they get that 1 gallon of gas is equivalent to 33.7kWh of electrical energy? Is that an accurate equation of joule of gas to joule of electricity?

chef
25 November 2010, 2349
Richard - My first impression was that "mpg-e" was superfluous. After further consideration, I think the EPA made the right choice to equate it to existing mpg. Gas stations are everywhere and people are accustomed to paying for gas (the vast majority of people [in the US] have only known mpg their entire lives!). It's primarily a way to compare costs, which is ultimately what matters to most consumers.

I like the annual operating costs on the EPA stickers (http://content.usatoday.com/communities/driveon/post/2010/11/volt-is-rated-93-mpg-on-electricity-alone-37-mpg-on-gas-generator/1). Look closely and you'll see that it also shows 36 kWh per 100 mi (360 Wh/mi). That sounds about right for the typical lead-foot. I hope that they'll eventually make the Wh/mi figure more prominent as EVs become more familiar.

As I had forgotten that Gas Is Cheap, I was surprised that the annual operating costs for EV-only vs gas-only modes are $600 and $1300 respectively. A savings of $700/yr in gas doesn't seem so hot in light of the Volt's price premium. As gas goes up, this figure would change quickly. Someone figured that the EPA's calculations assume $0.12/kWh, so if your utility has TOU (lower price at night) the electrical cost could be reduced substantially. 7c/kWh would bring the electricity cost down to $350.

Richard230
26 November 2010, 0831
What you say makes sense, Chef. But I still suspect that the general auto-buying public is just not properly educated about the technical aspects of electric vehicles (much less the technical aspects of anything technical) and is going to drive and use these vehicles in a way that will to capture headlines from disgruntled owners and other malcontents who don't understand how to drive this type of vehicle. Still, it should be an interesting time and I hope dealers are going to provide a high level of after-purchase vehicle support. In my opinion, every dealer that sells EVs should have one or more technical seminars about the vehicle soon after the buyer purchases it - the way Saturn dealers used to do before GM killed them off.

As you mention, the big problem right now is that gas is cheap. Eventually the price will rise and driving electric will become more common. I just hope the industry doesn't collapse due to too many products chasing too few buyers before that happens. On the other hand, if there is another oil embargo due to trouble in the Middle East, you will see EV sales skyrocket and the public will be on their knees begging to buy anything that runs on electricity. BTW, my electricity rate is around 13 cents per kWh and goes up the more you use.

Skeezmour
26 November 2010, 0909
6 cents per KWH here in the Pacific North West :) Now if I could find away to afford a Leaf.

chef
26 November 2010, 1105
Whoa 6c/kWh any time of day? I guess there's still plenty of hydro power to go 'round. Google built a huge data center in that region right next to a hydro dam specifically for the cheap power. I'm on the Green Choice program and get electricity from the wind farms in west TX. Well, electrons are electrons and there's way too many coal plants here, but at least my money is going to the wind farms. My rates are 7c/kWh for the first 500, then it jumps to around 14c/kWh (no TOU here). Multiple people in this household so costs average to ~10c/kWh. Adding an additional EV load would push that higher since it would all be in the penalty.

Richard - Early adopters tend to be more hard-core and seek out information themselves. The first wave of Volt buyers should be no different. 2012 might see an increase in average consumer purchases. If gas holds steady through then, a training program might be worthwhile. But if the last oil spike is any indicator, as gas prices go up people will look for any way to save $$. There was huge interest in hyper-miling. Although short-lived, interest was so high that the local news media had stories on it regularly.

DaveAK
26 November 2010, 1111
Most of our energy is hydro, but it's still 12c/kWh or so I think. And no time of use tarrifs which really sucks.

chef
26 November 2010, 1152
Some more back & forth discussion on the GM-Volt forum if you have time to burn...

http://gm-volt.com/forum/showthread.php?5715-Official-2011-Chevrolet-Volt-EPA-Fuel-Economy-Released

DaveAK
26 November 2010, 1209
Some more back & forth discussion on the GM-Volt forum if you have time to burn...

http://gm-volt.com/forum/showthread.php?5715-Official-2011-Chevrolet-Volt-EPA-Fuel-Economy-Released
I do have time to burn! I need to go to town for a couple of things, but really don't want to deal with Black Friday madness. :D

billmi
30 November 2010, 1036
Gizmag just ran a piece on the Volt's new window sticker.

IMHO, MPG Equivalent based on anything other than dollars per mile (which will fluctuate too often to put on a sticker) won't mean much to Joe consumer - it's nice to see a additional data on the sticker.

http://www.gizmag.com/new-fuel-economy-label-for-chevy-volt/17069/picture/125118/

Richard230
30 November 2010, 1546
They forgot to add the charge time using 120V. Certainly not everyone who buys a volt, or any other EV for that matter, will install a 240V charger in their home.

electrician
30 November 2010, 1646
The only reason GM came out with the Volt was to improve their average gas mileage for their cars to meet the ever tougher CAFE standards. They really don't care if they sell or not, as long as they are included in their lineup. The National Highway Traffic Safety Administration (NHTSA) proposed earlier this year that automakers must achieve a 25% increase in fuel economy from 2011 to 2015 model years. The Volt helps GM's mileage average.

lugnut
30 November 2010, 1849
The only reason GM came out with the Volt was to improve their average gas mileage for their cars to meet the ever tougher CAFE standards. They really don't care if they sell or not, as long as they are included in their lineup.

I thought the compliance to CAFE included the sales mix of models. So if they don't sell any (or many) Volts, they don't get any benefit.

electrician
01 December 2010, 1015
I thought it was an average of their production lineup? not what they sell, but what they offer to the public. I might be wrong, but I don't trust GM.

lugnut
01 December 2010, 1204
I thought it was an average of their production lineup? not what they sell, but what they offer to the public. I might be wrong, but I don't trust GM.

Got me wondering, so http://en.wikipedia.org/wiki/Corporate_Average_Fuel_Economy


Historically, it is the sales-weighted harmonic mean fuel economy, expressed in miles per gallon (mpg), of a manufacturer's fleet of current model year passenger cars or light trucks with a gross vehicle weight rating (GVWR) of 8,500 pounds (3,856 kg) or less, manufactured for sale in the US.

BaldBruce
01 December 2010, 1338
Uugghh. After reading that link, now I even know what a harmonic mean is!

billmi
01 December 2010, 1440
Which is nothing like playing a mean harmonica... honkin on bobo.

teddillard
01 December 2010, 1518
honkin on bobo makes your mileage drop :D

jpanichella
01 December 2010, 1609
honkin on bobo makes your mileage drop :D

I was waiting for somebody to say that. Thanks for doing it for me, Ted.