Chevy Volt rated at 93/37mpg | Hacker News Reader

Chevy Volt rated at 93/37mpg

engadget.com

12 pointsck236 comments

These numbers are meaningless; the EPA had to make up some kind of methodology for assigning a "mpg" number to a car which isn't actually burning any gasoline at all.

In my opinion it should say "Infinity miles per gallon" on the electric side of the label. I'm guessing that half the reason they don't is because they have these CAFE "average MPG standards" which they want to force automakers to adhere to, and throwing infinities into the averages tend to mess things up.

I don't know why people are so down on the Volt -- I think it's an excellent piece of technology, and probably the way of the future. An electric car with a petrol-powered generator to keep you going after the batteries are flat is the best of both worlds -- you can burn zero fuel most days, but still drive a thousand miles in a day if you feel like it.

I'm not sure "infinity miles per gallon" makes sense on the electric side. The EIA publishes statistics about power generation in the United States:

http://www.eia.doe.gov/cneaf/electricity/epa/epa_sum.html

Since 68.8% of power generation in the United States comes from non-renewable resources (coal, gas, and petroleum), it makes sense that the EPA would use some sort of system to describe the MPG for cars running on electric power.

Then why aren't all of the energy costs associated getting that gasoline to the pump factored into the cost of MPG on normal cars then? People are so quick to point out the 'hidden costs' of electric cars, while ignoring things like:

  * Drilling for crude oil
  * Harvesting crude oil
  * Shipping crude oil
  * Refining oil into gasoline
  * Shipping gasoline
  ... etc ...

They really should give it in miles-per-megajoule or something, though, rather than "mpg equivalent", which only serves to confuse people.

What is a "gallon equivalent" of electricity anyway? Is it the amount of electricity you'd get if you burned the gallon and generated electricity at 100% efficiency? Or the amount that you'd get if you used it to generate electricity with power-plant efficiency (which incidentally is pretty high)? Or perhaps it's the amount of electricity you get if you burn the CO2-emissions equivalent amount of coal? Or the dollar equivalent amount of coal? Or... well, there's a bunch of other possible definitions.

Miles per gallon of coal?

If you're going to try to come up with an equivalent number, are you going to base it on carbon emissions or on cost to the consumer? Either way, it will be highly variable: gas prices fluctuate relative to electricity prices, and different sources of electricity lead to different emissions per kWh.

At least with gasoline-powered cars, the differences between EPA estimates and real-world consumption are factors under the driver's control. This isn't the case with BS numbers for EVs, so the numbers end up being pretty much useless to the consumer. If the number is not going to be useful to the consumer, then there's no reason to mandate it be on the sticker.

If the number is not going to be useful to the consumer, then there's no reason to mandate it be on the sticker.

Having some sort of number there is useful; as electric cars become more common we'll need some way of comparing their efficiency. Right now you can find out that the Volt at 93 "mpge" is slightly less efficient than the Nissan Leaf at 99 "mpge". I'd still much rather have it in the less ambiguous units of miles per kilowatt hour.

(Or if they really want to appeal to physicists, they should give it in units of inverse force. 1 mile per kilowatt hour = 447.04 inverse MegaNewtons.)

Their chart is super confusing too, unless you stop and really study it and read the fine print.

Basically the most useful part on that chart is the lower right where it's 50% more cost effective per mile under 45 miles.

Maybe this is a "first gen" problem and they can get it to three, eventually four times as cost effective in a few years. I bet Japan or Germany will figure it out first.

Three or four times as cost effective? Not unless someone starts selling electricity for cheaper.

This is just rubbing up against the laws of physics. If you wanna move a one-point-something ton hunk of metal around it takes a certain amount of energy. All the components are operating at reasonably high efficiency, so you're not going to get a threefold increase in efficiency by any clever tricks.

Reducing car weight and profile will help too, we can't keep driving these huge cars (though it doesn't have to be super small either).

My electric bike can go nearly 40 miles @ 25mph on a 48v 20ah battery.

The difference is weight and wind profile.

So WTF is with 37mpg - my 15 year old car (with the weight of poor 1990's design, airbags, etc.) gets 35mpg (real-life).

I would love an electric car like the Leaf but if "Detroit" can't make a base car that gets good mpg, adding electric won't help solve the efficiency. Why not first make a car that by design can get 40+mpg in the CITY (not just averaged).

Why wasn't part of the bail-out condition that they have to build something like this in the USA:

http://www.businessweek.com/magazine/content/08_37/b40990604...

Why 37 mpg? Because when running in fuel-burning mode, the Volt is using the engine to turn a generator which produces electricity to turn the wheels. There's an inherent inefficiency in the extra step.

But that's the price you pay for being able to do your daily commute most days without burning any petrol whatsoever.

I have to think it's all the extra weight in there too?

The shape reminds me very much of the VERY efficient Honda 1990 CRX HF (60mpg)

http://www.engadget.com/photos/chevrolet-volt-dc-test-drive/...

vs.

http://www.google.com/images?q=CR-X+HF

Perhaps the measure should be "miles per dollar of fuel or charge", which would have to be averaged and could vary by region.

I partially look at hybrids and electric cars as a hedge against the possibility of Peak Oil making a significant difference in oil prices at some point in the next few years.

Might happen, might not. Regardless, I get to drive a fun new toy -- I find the experience of driving a hybrid to be fun (the sound, instant torque, etc).

And never mind the fact that in the vast majority of the US, you'll be burning coal, petroleum or NG to recharge it.

Your point being?

Electric cars need larger scale infrastructure changes beyond simply changing the cars or providing charging infrastructure but everyone always knew that.

Hypothetically:

You just spent $41,000 on a Volt. Let's assume you drive this thing to the very limit of its electric-only range pretty much every work day, or 35 miles (advertised). You'd spend about $225 on electricity over the course of the year to get around like this.

Your neighbor just bought a bottom-of-the-line Ford Fusion (non-hybrid, 22 MPG city) for a notch under $20k. Driving the same 35 miles every work day, they'll burn 1.6 gallons of fuel daily and where I'm from that translates to an annual fuel cost of $1,080, or $855 more per year than you.

It would take you 24 years (210,000 miles) at that kind of fuel cost advantage to offset the price you paid for the car.

You're not saving money. You're not saving the environment.

Then there's the fact that the Volt's battery pack will likely need to be replaced no less than twice (and likely at an extravagant cost) by the time it gets to 210,000 miles, and we all know that the rest of the car wouldn't last long enough to see this through to fruition.

In the EU at least, it seems the offerings are likely to be with a leased battery precisely for that reason. The batteries can also be used for lower-requirement purposes after being retired from vehicle use.

I don’t think electric cars are about saving money. I never heard that as a selling point.

And aren’t electric cars all about large scale infrastructure change anyway, not individuals curbing CO2 emissions? Say we find a way to satisfy our electric energy needs mostly without producing any CO2 within the next, say, thirty years. If our streets at that point are still full with gasoline cars we will be unable to reduce their CO2 emissions quickly. We consequently need to change the cars we are driving. As far as I know all proposed ways of doing that – whether hydrogen or electric – require large scale infrastructure changes and development of the right technology. Things like that take time.

If we don’t want to have only gasoline cars on the streets I guess we should start rolling out the first alternatives, well, probably right about now.

If they're not about saving money, why do people get concerned about their effective miles-per-gallon? If people were concerned about the environment, we'd be rallying the EPA to talk about the amount of greenhouse gases being laid out by the car's production and use. We'd also see people riding bicycles or walking to their offices that are a mile away instead of letting their car warm up for 15 minutes and driving.

There's noting wrong with wanting a car because it looks cool, because it has some hot new piece of tech, or because the amount of dollars you spend on your car somehow makes you feel better about yourself. And to those people, fuel economy makes little difference.

If they're not about saving money, why do people get concerned about their effective miles-per-gallon?

Reducing dependence on foreign oil?

Sure they are about saving money. At least it should be.

It gives you options about power source and an electric motor in itself is much more efficient than a mechanical "explosion" based motor.

We're just not quite there yet on a good, cheap, source of power. Unfortunately cannot plug in to a solar array for a week or two!

While an early adopter vehicle like this isn't about saving money at all (there are extremely few hybrid vehicles that economically pay off), a Volt with come with a lot of cachet. Sure there'll be the contrarians (seriously, the griping about the 37 mpg borders on the ridiculous. That is a very decent worst-scenario mixed-use value for a vehicle in the class of the Volt. But contrarians gotta hate), but overall most people will perceive it as a higher esteem vehicle.

People pay a lot of money for higher esteem vehicles. It funds most hybrids (which by themselves are seldom a net return).

There are currently no consumer power plants in the USA that burn oil.

But yeah coal is a huge problem (and the "clean" coal fallacy must die asap).

Source? I thought that Diesel was a fuel for peaking plants in the United States.

http://en.wikipedia.org/wiki/Peaking_power_plant

http://en.wikipedia.org/wiki/Load_following_power_plant

I will have to google a bit but Carter phased out oil based plants after the first crisis. I think it was called the "fuel use act".

Huh. Well I stand corrected:

http://en.wikipedia.org/wiki/Category:Oil-fired_power_statio...

But I also read elsewhere they only make up 8 percent of the total in the USA and are being phased out.

To counter this, places like Portland and Seattle get their electricity almost exclusively from Hydroelectric. For those who are really willing to subsidize the advancement of our independence on foreign oil, I suppose it could make some sense if they live in areas like that. I still think the Bicycle is a more elegant (and cheaper, more accessible and more disruptive) solution to the problem.

>But I also read elsewhere they only make up 8 percent of the total in the USA and are being phased out.

A fraction of a percent now.

http://www.eia.doe.gov/cneaf/electricity/epm/table1_1.html

It's not a sane choice; burning oil for electricity is absurdly expensive.

According to the EPA, it was 20% of NYC's electricity as of 2005:

http://www.epa.gov/cleanenergy/energy-and-you/how-clean.html

To quote `Sustainable Energy without the hot air' [1]:

"You’ve shown that electric cars are more energy-efficient than fossil cars. But are they better if our objective is to reduce CO2 emissions, and the electricity is still generated by fossil power-stations?

This is quite an easy calculation to do. Assume the electric vehicle’s energy cost is 20 kWh(e) per 100 km. (I think 15 kWh(e) per 100 km is perfectly possible, but let’s play sceptical in this calculation.) If grid electricity has a carbon footprint of 500 g per kWh(e) then the effective emissions of this vehicle are 100 g CO2 per km, which is as good as the best fossil cars (figure 20.9). So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply."

and

"I’ve looked up the performance figures for lots of electric vehicles – they’re listed in this chapter’s end-notes – and they seem to be consistent with this summary: electric vehicles can deliver transport at an energy cost of roughly 15 kWh per 100 km. That’s five times better than our baseline fossil-car, and significantly better than any hybrid cars. Hurray!"

[1] Full text available online. That's why I am not giving page numbers, just use a search engine.

>"I’ve looked up the performance figures for lots of electric vehicles – they’re listed in this chapter’s end-notes – and they seem to be consistent with this summary: electric vehicles can deliver transport at an energy cost of roughly 15 kWh per 100 km. That’s five times better than our baseline fossil-car, and significantly better than any hybrid cars. Hurray!"

I'm surprised MacKay said this, as it's misleading to compare heat energy (the heat content of a liquid fuel) with electric. That "five times better" figure basically comes from shifting the combustion of fossil fuel (and its thermodynamic losses) from the car to the power plant -- it's an artifact of the definition.

In fact, based on the EPA's Chevy Volt numbers (which may or may not be representative), it could be more efficient to burn gas in the Volt, than fossil fuel in a power plant for its electric engine. How I figure:

37 mpg on gas means 2.70 gallons/100 miles = 348 megajoules/100 miles (energy density of gasoline is 34 MJ/L [1])

On the electric side, it uses 36 kWh (130 MJ) electricity/100 miles. According to EIA figures, average US power plant efficiencies are [2]:

* for oil, 31% efficiency --> Volt uses 418 MJ power plant oil/100 miles

* for coal, 33% efficiency --> Volt uses 394 MJ power plant coal/100 miles

* for natural gas, 41% efficiency --> Volt uses 315 MJ power plant NG/100 miles

The CO2 emissions on electric are lower in the Volt, not because of an efficiency advantage, but because some of the electricity sources (hydro, nuclear) aren't fossil fuels. Likewise, the cost/mile is usually lower because the per-Joule cost of coal and natural gas are far lower than that of oil and gasoline.

[1] http://en.wikipedia.org/wiki/Energy_density

[2] http://www.eia.doe.gov/aer/txt/ptb1306.html

> I'm surprised MacKay said this, as it's misleading to compare heat energy (the heat content of a liquid fuel) with electric. That "five times better" figure basically comes from shifting the combustion of fossil fuel (and its thermodynamic losses) from the car to the power plant -- it's an artifact of the definition.

Yes, that may be a bit surprising, considering that he's very explicit about that topic in the chapter on heating houses. There he mentions that you can get >100% efficiency by burning gas to make electricity in the power plants, and then driving heat pumps in your home.

Hmm who changed my title on this thread BTW?

The fact it was originally hyped at 230mpg is kinda important.

Anyway, did anyone notice how they did the press release the day before Thanksgiving when the press is completely distracted/idle? What is up with that? Are they trying to hide it?

It was a trolling title. The EPA has been working out how they would rate electric vehicles, and by the original criteria the LEAF would have been rated at something like 367 mpg. The Volt hasn't suddenly become less efficient -- the rating criteria changed.

I wasn't trying to troll, was just disappointed. The original title was:

Chevy Volt fails hyped 230mpg and only gets 93/37mpg

That's valid because they didn't just get a 230mpg rating - they advertised the heck out of it, it was everywhere.

Then they quietly release this 93/37 rating the day before Thanksgiving when the news is asleep and people are distracted elsewhere.

Pft. My 5 year-old Peugeot 206 averages 60 mpg.

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