Is electric car fuel efficiency a fraud? Leaf gets 25 mpg?

[davefoc]

Ouch, "always" is "never" the right word to use . . .

For example, let's say you routinely drive a 250 - 450 mile round trip with 90% of that being on freeways at 70 mph. Which car would you find best?

I think a jetta diesel gets you there in back in one tank, maybe two, and at over 45 mpg. The Leaf will take you an extra day or two, depending on how you space the charging. The Prius will do it in two tanks, but the mileage will be lower than the jetta.



I can totally agree with that. But there is a difference between a motor and a vehicle . . .



And that is the difference between an EV and diesel vehicle.

Just a few quibbles with the above that don't take away from your point.

1. My buddy routinely gets about 50mpg with his Prius.
2. The range of my gasoline powered 2008 manual shift Honda Civic sedan for a long trip with steady driving is somewhat more than 450 miles. I routinely get about 400 miles with a mix of 70% 70 mph freeway and 30% suburban driving. My wife with her driving style and driving mix gets about 15% less mileage in a similar car.
3. One needs to be careful when comparing diesel mileage with gasoline mileage. Diesel fuel has more energy per gallon. Crude oil comes out of the ground as a mixture of various hydrocarbons. If gasoline vehicles were replaced with diesel vehicles extra energy would be required to convert lighter hydrocarbons to diesel. As it is now, I believe the current demand for diesel doesn't require the conversion of a significant amount of lighter hydrocarbons to diesel because the naturally occurring diesel fraction is about right to satisfy the demand.

 

[davefoc]

I know this is a bit off topic but are articles like this helpful or harmful to the development of new and better technologies?

Does it encourage new and positive changes or does it discourage new ideas by seriously tearing them apart while they are still in their infancy?

I doubt this article or similar articles have much actual effect. It was obviously a biased piece and I suspect that decision makers on whether to pursue a particular technology aren't strongly affected by this kind of thing.

But I think the issue is complicated. The subsidized conversion of corn to ethanol for fuel purposes is probably not justified in terms of its societal benefits. But the content of various articles on the subject have little effect on the funding for the program. The program is driven principally by pork barrel politics. There is an attempt to justify the program by promoting it as green policy and that undoubtedly is somewhat effective in providing cover for politicians from their ECO oriented constituency. However in the long run the effect of a lot of anti-ethanol articles eats away at the positive perception of the ethanol from corn programs and the programs will probably eventually die as a result. So sometimes articles can effect policy.

 

[Dr. Keith]

Just a few quibbles with the above that don't take away from your point.

There is plenty of room for quibbling in this debate. My main point is that the right vehicle depends on the intended use.

Another example: A chrylser minivan is more efficient than prius, if you have to move more than the prius can handle in a single trip.

1. My buddy routinely gets about 50mpg with his Prius.
2. The range of my gasoline powered 2008 manual shift Honda Civic sedan for a long trip with steady driving is somewhat more than 450 miles. I routinely get about 400 miles with a mix of 70% 70 mph freeway and 30% suburban driving. My wife with her driving style and driving mix gets about 15% less mileage in a similar car.

That is where the MPG stickers come into the picture: they compare the cars, not the drivers. (BTW, I may be wrong on the Jetta diesel available in the US, it seems to only get an EPA rating of around 40 MPG. Don't get the smaller diesels in the states apparently. Mea culpa.)

But the MPGe compare EVs to one another, not to ICE vehicles. Think of it as crash safety tests. A five star crash safety rating for a very small car does not mean that the car is as safe as a midsize or larger car with the same star rating. The ratings are for comparison within the range of cars.

I do think that we will move to a $/1000miles sticker with some standardized pricing for fuel/electricity. The problem is that fuel and electricity pricing vary greatly with time and location. So, this method will be just as misleading as the current method.

Same applies to CO2/1000miles ratings. The CO2 from different electricity sources will vary.

EVs are going to be a significant factor in reducing our usage (or at least the growth in usage) of oil. They are coming and we just need to figure these things out as we phase them in.

 

[Dr. Trintignant]

In that case, you seem to be agreeing with the blogger that the EPA's MPGe figure is rather arbitrary, a stab in the dark at best? Or am I misreading you here.

(I don't care to get into their accusations of "fraud" at the moment, actually, since that's a broader issue which the blogger provides no evidence for.)

The EPA figure is arbitrary, but that alone can't be held against it--any metric must be to some extent arbitrary. It is inevitable when boiling a complex process down to a single number.

The EPA figure works well enough for comparative purposes between electrics and plug-in hybrids. It is also--somewhat coincidentally--not too far off the mark when it comes to a cost comparison. If gas costs $3.50/gal, then dividing by 33.5 kWh/gal we get $0.104. Depending on where you are in the country, electricity may be more or less expensive than this.

If the link authors wish to be taken seriously, they should state their intent. Intent is not normally of great concern in the sciences, but this isn't exactly a scientific question--it's more of a social one. It is easy enough to find the raw performance figures of these cars; the purpose of the EPA numbers is to allow an average consumer to make comparisons. Unless the EPA number is enticing consumers to purchase vehicles not in their interest, it's tough to say that it's truly wrong.

On the other hand, a figure of 23 MPG would actively mislead consumers into purchasing the wrong automobile. A gasoline-only car rated at 23 MPG would both pollute and cost more (considering only fuel costs, of course) almost everywhere in this country.

- Dr. Trintignant

 

[Dr. Trintignant]

So far, there has been no ringing endorsement of the number.

No, but as I've said any metric is necessarily somewhat arbitrary.

None of the figures that the EPA puts on a Monroney sticker are useful in a purely technical sense. They are based on conditions that may be close to some national average, but do not and can not match any individual consumer. If one wants technical specifications, they are certainly available, but the EPA does not use them because consumers do not understand them.

So any critique of the number must be on this basis. One may certainly argue that some other metric would better serve the public, but multiplying by an unrealistic efficiency figure is not an improvement.

- Dr. Trintignant

 

[Dr. Trintignant]

It would make some sense because at least it would include the inefficiency of some form of conversion of heat into useful energy, which is necessary in any case.

Some heat engines are only 1% efficient. Why not multiply by that number instead?

The link authors chose an unrealistic efficiency number to multiply by, and then didn't bother to defend why generation efficiency is even relevant (since coal is not the only source of electricity, or even the dominant one in all states).

Basically, I'm not defending the specific numbers of the webpage quoted in the OP; I'm agreeing with its general point that the EPA's numbers are wrong and with the general reasoning as to why they're wrong.

To state that something is wrong, one must correctly look at what was stated in the first place. The link authors pinned their own definition of "equivalency" on the EPA's numbers, and then went to demonstrate (poorly) that the numbers were wrong on that basis. But the EPA never stated that MPGe took end-to-end efficiency into account.

Perhaps one could argue that the EPA is giving mixed signals, and that consumers are reading into MPGe more than they should. If so, then one must ask on what basis they are being misled. Cost? Pollution? Something else? The link authors don't address this, and thus don't even begin to make a valid case that the EPA figure is "wrong," let alone fradulent.

- Dr. Trintignant

 

[Dr. Trintignant]

I know this is a bit off topic but are articles like this helpful or harmful to the development of new and better technologies?

Does it encourage new and positive changes or does it discourage new ideas by seriously tearing them apart while they are still in their infancy?

Articles like this are harmful because they spread misleading information.

However, articles that carefully analyze the meaning of the numbers, and under what conditions they fail to hold, are useful--no matter what ultimate conclusions they come to.

The Volt and Leaf are not optimal under all conditions, and do not perform like a 90+ MPG fossil fuel car all the time. As Dr. Keith mentions, a small diesel car is likely better for long trips, and a minivan is better when cargo needs to be hauled around.

Infant technologies should not get a free pass on criticism just because they're new, but the criticism should have some validity to it.

- Dr. Trintignant

 

[drkitten]

It sounds like you think that the main purpose of the sticker is to make it easy for buyers to calculate how much money it will cost them to run the car.

Nope. It's to allow them to estimate whether this car will cost more or less than the one they're currently operating.

In that case, the question for electric cars is how many miles the car will go for each kilowatt-hour of electricity used, because electricity is sold by the kilowatt-hour.

No, because most people have little idea how many miles they drive in or and no idea of how many kWh equate to the energy content of a gallon of gas.

What they do know is that their current car gets (e.g.) 40 mpg, and that the car they're eyeing up gets the equivalent of 45, then it's likely to be a wash (depending of course on the local price of electricity).

If their current car gets 12 and the new one gets 80, there's likely to be a big difference.

It only invites dubious comparisons to gasoline-powered cars.

You say "dubious," I say "cognitively salient." Tell you what -- you can sell cars to everyone in the USA that's passed high school physics, and I'll sell cars to everyone in the world who hasn't but who understands MPG as a measure of fuel efficiency, and we'll see which one of us has a better sales strategy.

 

[Hindmost]

well, the conversion for a kw-hr to gallon of gas is

1 kilowatt hour = 0.027,322,404,372 gallon

It might be interesting to run some calcs....electric cars are part hype since the cost of batteries and the materials are not really included in the long term efficiency. I'll be back...with some numbers.

glenn

 

[Piggy]

I would say not, for the simple reason that they're trying to charge electric vehicles with the cost of delivering energy from the production site to the car, but trying to avoid doing the same for gasoline vehicles.

The gas at your local Exxon station didn't come from there; it arrived by truck or pipeline, with all the transportation costs.

Yeah, that was actually part of my initial response to the person who sent me the link. I hadn't considered the differences in efficiencies of the different types of engines, but I've passed that along as well.

I'm still trying to get my head around the Monroney number for an EV, tho, and how to describe it (to myself and others) in ways that are easily comprehensible, as well as how to come to something like a range of accuracy for the estimate.

 

[Piggy]

I doubt this article or similar articles have much actual effect. .

I'm not so sure. I think a lot of people are on the fence about the viability of "green" tech, and I know a lot of folks are highly suspicious of gov't agencies right now.

The post presents a very easily comprehensible meme.

If the reality is much more complex, guess which one wins.

 

[Piggy]

The EPA figure is arbitrary, but that alone can't be held against it--any metric must be to some extent arbitrary. It is inevitable when boiling a complex process down to a single number.

The EPA figure works well enough for comparative purposes between electrics and plug-in hybrids. It is also--somewhat coincidentally--not too far off the mark when it comes to a cost comparison. If gas costs $3.50/gal, then dividing by 33.5 kWh/gal we get $0.104. Depending on where you are in the country, electricity may be more or less expensive than this.

If the link authors wish to be taken seriously, they should state their intent. Intent is not normally of great concern in the sciences, but this isn't exactly a scientific question--it's more of a social one. It is easy enough to find the raw performance figures of these cars; the purpose of the EPA numbers is to allow an average consumer to make comparisons. Unless the EPA number is enticing consumers to purchase vehicles not in their interest, it's tough to say that it's truly wrong.

On the other hand, a figure of 23 MPG would actively mislead consumers into purchasing the wrong automobile. A gasoline-only car rated at 23 MPG would both pollute and cost more (considering only fuel costs, of course) almost everywhere in this country.

Well, in practical terms, if the number is actually arbitrary, that certainly can be held against it, for psychological reasons.

When people are presented a number like that, and they're told that this car gets the equivalent of 93 mpg, then someone comes along who can demonstrate that this number is unreliable, that can be extremely damaging.

So if someone's asking, well, is this an accurate number, or is it unreliable, if you say that it's not hard and fast, you've got a problem on your hands.

Right or wrong, when most folks are presented a number like that, they expect that there's some simple equation behind it.

For example, MPG is very easy to understand. I can calculate it myself. I put a certain number of gallons of gasoline in my tank and I drive a certain number of miles before it runs out.

So if EPA says that an e-car gets the equivalent of 93 MPG, it can be a bit of a head-scratcher if there's no clear, simple explanation of what that means.

 

[Piggy]

Articles like this are harmful because they spread misleading information.

However, articles that carefully analyze the meaning of the numbers, and under what conditions they fail to hold, are useful--no matter what ultimate conclusions they come to.

The Volt and Leaf are not optimal under all conditions, and do not perform like a 90+ MPG fossil fuel car all the time. As Dr. Keith mentions, a small diesel car is likely better for long trips, and a minivan is better when cargo needs to be hauled around.

Infant technologies should not get a free pass on criticism just because they're new, but the criticism should have some validity to it.

I'm not sure what you mean by "should".

The fact is, for its intended audience, this is a nice piece of doubtcasting.

And if there's an effective response to it, that response cannot be vague or overly complex.

If there's not a pretty simple layman's explanation to be had of EPA's methodology -- a thumbnail description of what MPGe "means" or how EPA arrives at it -- then it's dead in the water, I'm afraid.

I mean, after all, when that number goes on a sticker, it's natural for folks to assume that it is derived by some rather precise method -- otherwise, there should be a range rather than a single figure.

If that figure is questioned, and the response is that the number isn't precise, then you can expect that folks are going to question the validity of the entire scheme.

 

[Piggy]

Perhaps one could argue that the EPA is giving mixed signals, and that consumers are reading into MPGe more than they should. If so, then one must ask on what basis they are being misled. Cost? Pollution? Something else?

I would say they're being misled by the assignment of a single number if that number is so imprecise as to make a range more appropriate.

I doubt that your average car buyer would even consider cost or pollution when looking at a number like that. After all, if the number were about cost it would be in dollars, and if it were about pollution, well, God knows what units it would be in.

Instead, the MPGe figure attempts to equate "miles per gallon" which will make the vast majority of folks think about fuel burned for a certain distance driven.

So if you say that an EV gets an equivalent MPG, then they're bound to think that this vehicle will go a certain number of miles for a particular quantity of source fuel (such as coal) burned.

And if it turns out to mean something else, they're going to feel cheated.

 

[davefoc]

I'm not so sure. I think a lot of people are on the fence about the viability of "green" tech, and I know a lot of folks are highly suspicious of gov't agencies right now.

The post presents a very easily comprehensible meme.

If the reality is much more complex, guess which one wins.

You might be right. The more I think about this the more it seems like the EPA should not have promoted this kind of metric. Although it would have been subject to immediate criticism and need periodic adjustments I think a fuel cost per mile metric is the one that the EPA should have promoted. Something like assume a gas price and a kwh price and give people a number that is useful and not misleading to the extent the MPGe thing is.

Of course, even a fuel cost per mile metric has difficulties. How do the maintenance costs stack up between the two vehicles is the big issue not incorporated there. My guess is electric vehicles win on maintenance costs until it's time to replace the battery pack and the cost of that might eliminate most of the electric vehicle operation savings.

If the EPA was going to promote something like an MPGe rating then it might have been a good idea to develop a complex MPGe rating that attempted to take into account the various issues. Although this is difficult to the point of almost impossible to do because there are subjective issues and issues that are impossible to estimate, a reasonable cut at it with published assumptions might have been possible. That way there would have been a metric for people who just want to know how the mileage cost of the electric vehicle compares with their gas vehicle and there would have been a metric for people trying to get a rough feeling for the practicality of a change to a mostly electric vehicle fleet.

 

[Arthur Mann]

I think a fuel cost per mile metric is the one that the EPA should have promoted.

Aside from the fact that the EPA is a useless bureaucracy, this is a profoundly stupid idea. Monetary costs of things rarely have even a tangential relationship to the real world. The price system is entirely artificial and controlled centrally, by human beings, so the idea that it can be used in some sort of objective analysis is laughable.

Something like assume a gas price and a kwh price and give people a number that is useful and not misleading to the extent the MPGe thing is.

How about we just move as fast as possible toward the sanest technology, and ignore the monetary costs, which bear no resemblance to and really have no control over objective reality. The scientific method may be helpful here. Political "solutions" are doomed to enslave us all and poison the whole planet in the process.

 

[Piggy]

Aside from the fact that the EPA is a useless bureaucracy, this is a profoundly stupid idea. Monetary costs of things rarely have even a tangential relationship to the real world. The price system is entirely artificial and controlled centrally, by human beings, so the idea that it can be used in some sort of objective analysis is laughable.

From a consumer's POV, I don't think it's laughable at all. In fact, it might be a very smart move for EPA.

Of course, they'd have to use averages, but that's something almost everyone can understand.

It doesn't matter that the price system is a human invention. People want to know how much it costs them to run one vehicle versus another.

 

[Dr. Trintignant]

Well, in practical terms, if the number is actually arbitrary, that certainly can be held against it, for psychological reasons.

All this argues for is no labeling requirements at all since again, all metrics are to some extent arbitrary. I hope the problems with that approach are obvious.

For example, MPG is very easy to understand. I can calculate it myself. I put a certain number of gallons of gasoline in my tank and I drive a certain number of miles before it runs out.

Yes, and if you do that you'll find that your numbers don't match the EPA. The highway numbers are calculated at 48 MPH, for instance (and not because they simulate traffic). Who drives that slowly?

So if EPA says that an e-car gets the equivalent of 93 MPG, it can be a bit of a head-scratcher if there's no clear, simple explanation of what that means.

The average consumer neither knows nor cares, and does not have the education to understand a technical explanation if it did exist. The tiny fraction of consumers that are interested in this information can easily seek it out.

Please, at least skim this link to see how utterly resistant consumers are to any change in the labeling that goes beyond the familiar "MPG".

I'm not sure what you mean by "should"

I mean it in the same way that I mean "teachers should not teach creationism in schools." Of course they do in practice, and in may be in their best short-term interest if the parents demand it. That does not mean it's a good thing in any objective sense.

If there's not a pretty simple layman's explanation to be had of EPA's methodology -- a thumbnail description of what MPGe "means" or how EPA arrives at it -- then it's dead in the water, I'm afraid.

For better or worse, the EPA only has to go so far in listening to public opinion. They're a government agency, of course, and within bounds they can do as they please.

But I don't get your argument in any case. There is no layman's explanation for the current MPG numbers on cars. The driving patterns they use are complicated and can't easily be replicated. The hope is just that they are close enough to most people's driving pattern to be useful.

Instead, the MPGe figure attempts to equate "miles per gallon" which will make the vast majority of folks think about fuel burned for a certain distance driven.

It seems to me that most people view MPG as an opaque figure that only distantly relates to actual miles and gallons. Instead, it's seen as a somewhat generic figure of merit (how many people actually use the posted MPG numbers to compute their fuel costs?). In this sense, the MPGe figure is more reasonable.

- Dr. Trintignant

 

[Piggy]

All this argues for is no labeling requirements at all since again, all metrics are to some extent arbitrary. I hope the problems with that approach are obvious.

Yes, the problems with that approach are obvious, but that doesn't help with the issue at hand, which is to explain to the causal reader why the blog post is inaccurate when it (supposedly) exposes the MPGe figure as unreliable.

The blog post, after all, was not addressing the issue of labeling requirements.

 

[Piggy]

Yes, and if you do that you'll find that your numbers don't match the EPA. The highway numbers are calculated at 48 MPH, for instance (and not because they simulate traffic). Who drives that slowly?

True, but that difference is not a factor of 4, which is what the blog post alleges.

If the blog post is that widely errant, then there should be a simple, objective explanation why not.