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Chevrolet Volt window sticker
93 mpg on battery power, 37 mpg on gasoline power

After a cluster bomb that was unleashed yesterday when the Nissan Leaf was rated for an EPA estimated 99 mpg -- even though it is a "battery only" vehicle -- General Motors is dropping a bunch of digits on us when it comes to the EPA rating for its Chevrolet Volt.

According to the window sticker that will be plastered on all new Volts sold in the U.S., the vehicle is rate at an equivalent of 93 mpg when running on electricity, and a more sedate 37 mpg when the gasoline engine kicks in after the battery is depleted. This two figures combined give the Volt a "composite" rating of 60 mpg.

And here are some more numbers -- the Volt will have an official "battery only" range of 35 miles, while the total driving range (taking into account the batteries and the gasoline tank) will be 379 miles.

When the Volt was first announced, GM said that the vehicle would have a 40-mile range when running on battery power. The company recently revised that figure to 25-50 miles.

The Volt will go on sale later this month with a price tag of $41,000 before a $7,500 federal tax credit.

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60 "Combined" ? How is this calculated?
By rangerdavid on 11/24/2010 4:56:30 PM , Rating: 0
I do this:
35 x 93 = 3255
379 X 37 = 14023
3255 + 14023 = 17278 / (35+379) = 41.7343

RE: 60 "Combined" ? How is this calculated?
By Jeremy87 on 11/24/10, Rating: 0
By rangerdavid on 11/24/2010 7:08:22 PM , Rating: 2
Ahh, a more elegant solution. Thanks.

By Solandri on 11/24/2010 7:26:56 PM , Rating: 4
Average car is driven 12000-15000 miles per year. Split the difference and call it 13,500 miles per year. Assuming it's a commuter car, it's driven 250 days a year, or 54 miles a day.

If you drive 54 miles in a day, 35 of which are on battery, 19 are on gasoline.

19 miles @ 37 mpg = (19 miles) / (37 miles/gallon) = 0.514 gallons
35 miles @ 93 mpg = (35 miles) / (93 miles/gallon) = 0.376 gallons

Total miles = 54. Total gallons = 0.890.

54 miles / 0.890 gallons = 60.7 mpg

RE: 60 "Combined" ? How is this calculated?
By nafhan on 11/24/2010 5:22:58 PM , Rating: 2
I think they take into account the fact that most people won't be driving it to empty. Do the same calculations, but replace 379 with 50, and you end up with ~60MPG. In other words, they expect most people to drive about 85 miles.
Either way... I think using MPG on an electric vehicle is confusing at best.

By rangerdavid on 11/24/2010 7:11:21 PM , Rating: 2
Maybe just ditch the "MPG equivalent" and just state the range per 4-hour charge?

Or better yet, just state the miles per 10 Kw hours or something? That would take into account the progressively more efficient electric motors and transmissions, so you could compare electric-to-electric better in the future, i.e. "My new car gets 25 Miles-per-Kilowatt-Hour, my old one only got 21"

RE: 60 "Combined" ? How is this calculated?
By Solandri on 11/24/2010 7:38:37 PM , Rating: 3
Do the same calculations, but replace 379 with 50, and you end up with ~60MPG. In other words, they expect most people to drive about 85 miles.

This is a common mistake people make with MPG. When you average two MPGs, it's not

(MPG1 + MPG2) / 2


2 / [ (1/MPG1) + (1/MPG2) ]

For cases where you're averaging different numbers of miles at different MPG, it's

(miles1 + miles2) / [ (miles1/MPG1) + (miles2/MPG2) ]

You have to do this complicated conversion because MPG is the inverse of fuel consumption. MPG tells you how many miles you can go on a gallon of fuel, not how much fuel is needed to travel a certain distance. The rest of the world uses L/100km for this reason (kinda like gallons per 100 miles). You'll notice the EPA is trying to correct this with the electric/hybrid ratings - it's listing electricity consumption in kW-hr per 100 miles.

By Targon on 11/26/2010 5:51:18 AM , Rating: 2
As others have mentioned, the key is to look at how far you have to drive each day, and "averages" won't work here. The mpg rating(using miles per American gallon) does not break out highway miles vs. city miles per gallon. For those who live right in the city they work in, you may be able to get away with all electric on your commute, but MOST people live outside the city they work in, and a place like New York City has a VERY large area where you could have a 30 mile commute each way and still be "in the city".

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