How Should the Chevy Volt's mpg be Calculated?

[admin]

A challenge besides just mass producing the Chevy Volt, will be determining its EPA rating.

After all, the EPA has historically been amount miles per gallon. Since the Volt will go for 40 miles without gas, defining the car’s efficiency purely in terms of mpg just wont do.


From conversations I’ve had with officials, GM has been thinking about this issue since day one. Protocols have been developed, for example at Argonne National Lab (ANL), on how to calculate efficiencies in E-REVs. The ANL method involves driving the car over several EPA cycles until the ICE kicks in, and then drives it one more (each 6 miles). Then the mpg is calculated by dividing the miles driven by the number of gallons used and is adjusted for electric usage (see source).


MotorTrend is now reporting “word around Detroit is GM and the EPA are apparently duking it out over the Chevy Volt.”


The report indicates that the Volt can cover the EPA cycle using the gas engine 15% of the time, resulting in a fuel efficiency of just greater than 100 mpg. Reportedly the EPA wants to calculate the mpg based on what it would take in total if the ICE had to refill the battery at the end. This supposedly would lead to 48 mpg. That number of course wouldn’t set the Volt too far away from standard hybrids, and if it held would certainly confuse and mislead the buying public.


Of course, the Volt isn’t designed to have the ICE recharge the battery, it just wont happen. The car is designed to arrive to destination at roughly 30%-35% of the battery’s state of charge (aka customer depletion point). Therefore calculating in a theoretical filling of the battery is plain nonsense.
Obviously this is just the beginning of what will likely be a lengthy debate and I applaud MotorTrend for bringing it up. However, the facts of the article considering its lack of sources and references, brings its validity into question.


How do you think the Volt’s mpg should be determined?


Source (MotorTrend)

[FrayAdjacent]

MPG, or Miles Per Gallon (of gasoline) should be a separate rating for the Volt. It should ONLY be rated on fuel consumption during a normal driving cycle when the battery is at the depleted level.

MPC (Miles Per Charge) or MPkW (Miles Per kiloWatt) should be a separate stat, and should rate consumption based on the amount (in kW/h) needed to recharge the battery after normal driving of a certain range.

Both should be based on the EPA Fuel Economy methods.

[Tagamet]

Thanks Lyle!
I still think that WHATEVER method is used, it should be visual e.g. the Energy Star rating. Humans learn best visually, then aurally, then multisensorally.
JMO,
Be well,
Tag
"LJGTVWOTR!!" ©

[rickwolff]

I couldn't agree more that basing the Volt mileage on having the ICE completely recharge the batteries in ridiculous. Unless I'm confusing myself, that would be similar to refilling a gas tank on an ICE car and using BOTH the gas burned PLUS the amount used to refill in calculating MPG.
I anticipate my actual experience with the Volt will use very little gasoline. Even though I am a residential realtor I rarely drive more than 40 miles a day. Perhaps 20% of the days I would drive more - up to 80-100 miles. Presently my Volt would be recharged with Nuclear generated electricity (our source in Raleigh NC), but I am looking into and anticipate eventually getting a PV system.

[pdt]

One option would be to just accept the complexity of the vehicle and give the facts. Something like (edit: You’ll have to use your imagination for the formatting as the spacing gets removed on my browser: I tried to make it look pretty!),

City Hwy
Electric Mode
Range 40 32
MPkWh 5 4
$/mile ($0.10/kWh) $0.02 $0.025

Hybrid Mode
MPG 50 50
$/mile ($5.00/g) $0.10 $0.10

You could also have an “energy star” rating similar to what goes on appliances. Something like,

This vehicle will cost $500/year in electricity/fuel costs, then have the slider symbol showing lowest and highest for vehicles in this class, which will have a minimum of $500 and maximum of ~$2000).

It’s more complicated, but it’s reality.

[Kelemvor]

I'd say to have 2 ratings.

The whole rating should take into account that it doesn't even use gas for the first 40 miles.

So fill up the tank and charge up the battery. Drive it until it dies. Divide the TOTAL miles by the gas used to get the actual viewed Miles per Gallon.

But then of course you can take a dead battery and just run it on gas to see what the mileage rating for that would be too. But that would only tell half the story if someone wasn't familiar with how the Volt really works.

You could make an argument either way.

[Tagamet]

Rickwolf said
I couldn't agree more that basing the Volt mileage on having the ICE completely recharge the batteries in ridiculous. Unless I'm confusing myself, that would be similar to refilling a gas tank on an ICE car and using BOTH the gas burned PLUS the amount used to refill in calculating MPG.

I think that this is a great example.
Be well
Tag
"LJGTVWOTR!!"

[Dave G]

There are 2 issues here:
1) Explaining to car buyers how much gasoline the Volt will use.
2) Rating the Volt MPG for CAFE fleet standards.

For #1, I think it’s a no-brainier. Just advertise the Volt as 40 miles all electric, and then 50 MPG after that. People will get it. This is much easier to understand than plug-in parallel hybrids. The EPA should allow this type of rating for all extended range EVs, and it should be shown in a standard way on the sticker and in advertisements.

For issue #2, I would say average Volt drivers will run 85% of their driving on electricity, so that would be 333 MPG. This number should also be on the sticker and in advertising, as it is valid for comparison with plug-in parallel hybrids.

For details on the 333 MPG number - consider 1000 miles of driving, 850 of which are electric, 150 on gas. At 50 MPG, the Volt would use 3 gallons. So you’ve gone 1000 miles on 3 gallons of gas.

[pennor1]

I want the MPG computed on a level playing field. So what is that you ask? Treat the Volt just like every other vehicle in the tests. Don't modify the test to some non-real-world senario that does not reflect daily driving. So if the Volt comes up in excess of 100 MPG, that's the way it should be presented on the sticker. That's what the customer will see when he uses the car. And after all, that's what the EPA tests are all about. Giving the potential customer acurate comparitive information to make an infomred buying decision.

If in the end the EPA forces Chevy to run a test that does not reflect the real operating parameters of the car, I can only suspect that Toyota has paid someone off big time. After all, a 100 MPG Volt will really make the other hybrids look really pathetic in vomparison.

[twist]

hi all,

The question of MPG rating is a good one. I feel the only way to avoid a conflict with the EPA is to see it their way. Simply post the MPG as 50+/50+ with additional information below the rating.

50+/50+

+This vehicle utilizes battery power which can greatly increase the posted EPA figures.

twist