MPG equivalent

[malcolm]

The value on the TM homepage has jumped from 135 to 256. Anyone got any details on this?

Presumably this is for the smaller American gallon, so us Brits can expect to see around 307 miles to the gallon (equivalent)! :biggrin:

[TEG]

That is odd. I wonder what has changed. So many places I see a rule of thumb of 33kWh = equivalent of 1 gallon of gasoline. So the simple calculation of 220 * 33 / 54 = 134 MPGe

Check the end of this document (http://www.pabulletin.com/secure/data/vol36/36-49/2425.html):

Amount Equivalent to
One Gallon of Gasoline
@ 114,500 Btu per gallon = 33.558 KWH

[MDR]

Here's a couple of quotes from the owners site:


Hi everyone,

Zak asked me to jump in here since I'm the engineer responsible for EPA range/efficiency testing and generating the MPG data.

The EPA MPG calculation is specified in the Code of Federal Regulations, section 10 part 474. This regulation defines an equivalence between gasoline and electricity of 82.049kWh/gallon. http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2000_register&docid=00-14446-filed.pdf (http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2000_register&docid=00-14446-filed.pdf)

You can then calculate: mpg = kWh/gal / kWh/mi = 82.049 / 0.321 = 256mpg

The 0.321kWh/mi value comes from our range testing that is certified by EPA. However, as Zak correctly noted, the EPA has not had a current procedure for EV testing since 2003. Instead, EPA defers to the procedure specified by CARB, which is the Society of Automotive Engineers recommended practice "SAE J1634 Electric Vehicle Energy Consumption and Range Test Procedure". This procedure uses a chassis dynamometer, and a paraphrased version would say 1) start with a fully charged battery, 2) drive the vehicle over the test cycle until empty and measure the miles driven, and then 3) recharge the battery to full and measure the electricity used.

From our latest testing, the results for city/highway cycles were range of 231/224 mi and electricity use of 0.316/0.327 kWh/mi respectively.

As defined by EPA, you combine the city/highway data using a 55%/45% weighting: 0.321 kWh/mi = 0.55*0.316 + 0.45*0.327

So the MPG number depends on what equivalence you assume for electricity -> gasoline. There are many approaches to this, each with their pros and cons. Some people think that MPG is meaningless for EVs, but there are many others who want to know what the number is. Tesla has decided to quote the mandated EPA 256mpg number. The 135mpg value is an outdated non-EPA estimate, and I'm sure we'll be updating the website soon.

thanks
Andrew Simpson http://www.teslamotors.com/owners/forum/avatars/tesla_badge_blackbg.gif Posted by AndrewS on May 22, 2008.



It's actually a weird situation. The EPA requires us to use their definition on our labeling, even though we know that the more accurate energy equivalence is somewhat lower. We made the decision to always communicate the higher number with clear labeling that the number is the EPA equivalent. The actual energy equivalent is a bit below the 135 that is currently on the homepage - so we need to update that.

We thought about only communicating what we believe to be the more accurate number, but then you have the problem of the label saying something different and the problem of everyone else using the higher, official numbers. ZENN, for example, quotes about a 250 mpg.

Chalk it up to being hamstrung by the bureaucracy. Somewhere along the way the EPA decided to change the laws of physics to increase the energy density of fuel to benefit CAFE equations for the big companies.
http://www.teslamotors.com/owners/forum/avatars/tesla_badge_blackbg.gif Posted by Darryl on May 31, 2008.

[doug]

Thanks for the info, MDR.

Most references I can find for the energy content in 1 gallon of gasoline convert out to 33 to 38 kWh. 82kWh is quite a jump (over 215%).

I don't really understand this statement by Darryl:
Somewhere along the way the EPA decided to change the laws of physics to increase the energy density of fuel to benefit CAFE equations for the big companies. How is that supposed to help big companies with CAFE calculations? All of a sudden everyone looks a lot less efficient.

[Kardax]

In my opinion, MPG is meaningless for EVs.

Gasoline cars get a City/Highway rating.
EVs should get a City/Highway range rating.
Plug-in hybrids of any kind should get both ratings, showing EV range and gasoline fuel economy.

Simple :)

-Ryan

[Chris H.]

This will turn into a "Crisis of Credibility" for Tesla Motors, mark my words...

[stopcrazypp]

Thanks for the info, MDR.

Most references I can find for the energy content in 1 gallon of gasoline convert out to 33 to 38 kWh. 82kWh is quite a jump (over 215%).

I don't really understand this statement by Darryl: How is that supposed to help big companies with CAFE calculations? All of a sudden everyone looks a lot less efficient.

From what I am reading from the link given by MDR, it still uses the 33,705Wh/gal conversion factor but it factors in average efficiency of US fossil fueled powerplants & transmission and efficiency of petroleum refining and distribution. So far it's fine, except I like the consistent straight 33,705Wh/gal which doesn't change over time or depend on your local powerplant. It's adequate for plug-to-wheel efficiency. You can find the efficiency for specific powerplants and factor that in later for fuel-to-wheel efficiency.

Then they have this "fuel content" factor that they don't explain very well that boosts the number 6.67 times. Sounds like it's just a boosting factor for alternatively fueled vehicles from the comments section of the document. So that's just artificially inflating the efficiency numbers of alternatively fuel vehicles based on it's "benefits". It's an incentive factor to help boost a manufacturer's CAFE.

I'm sticking to the 33,705 Wh/gal number, which seems to the most scientifically sound number for plug-to-wheel efficiency conversions. MPG for electric vehicles don't make much sense (Wh/mi is much better), but it's still useful for comparing, esp for explaining to the layman.

Since we are talking about efficiency anyways I used the 0.321kWh/mi provided by Tesla and then the 12,307 Wh/gal number given in the EPA document which factors in the avg efficiency of US fossil fuel plants, transmission, petroleum refining & distribution and came up with 38.34mpg. Which means on average, powered by US fossil fuel plants, the efficiency from fuel-to-wheel in the Tesla Roadster is about 38.34mpg, which is not bad. The Lotus Elise SC (probably the closest gasoline powered car to the Tesla Roadster) gets about 20/26 mpg.

[TEG]

Some people will look at the MPGe numbers as a way to estimate costs to operate. For instance, how much do you pay for the electricity to drive 100 miles, compared to drive 100 miles in a gasoline car. A Prius could go maybe 100 miles on 2 gallons. Using $5/gallon gas thats $10 for 100 miles. So ~$0.10 per mile. If we said an electric car costs $0.02 per mile, then the EV is 5x cheaper per mile than the gas car. Given 50MPG for a Prius, then the EV would be in line to say that it gets 250MPGe.

Now if you go back a few years, gas was closer to $2/gallon, not $5/gallon, so it would line up better to say 135MPGe back then.

For this reason alone, it makes sense to permit higher MPGe if the cost of gas has gone up so much more than the cost of electricity.

Just another way to look at it. And yes my numbers are horribly rounded.

[malcolm]

Tesla's hands would seem to be tied by the EPA so I think it's unfair to lay gloom at their door over this one Chris.

Although I agree with Kardax that an mpg value is meaningless for BEVs, it could all become unnecessarily complex in a couple of years with the sales literature for REEVs.

Miles per charge, electricity cost per mile need to be promoted and explained clearly rather than publishing these mpg equivalent values.

In the meantime, I'm not sure what Tesla can do. 300 mp(imperial)g sounds like science fiction. Yet that is the consequence of the EPAs calculations. Does publishing this encourage the EV doubters and damage Tesla's engineering credibility?

[mt2]

I have to chirp in with my "me too" post; MPGe is irrelevant. It depends on what you mean by "equivalent".

As an average consumer, my bottom line is my pocketbook. If I switch from an ICE to an EV but keep all my driving habits, I'd measure the difference in my energy costs. That, of course, is totally irrelevant for anyone else who would be switching from a different vehicle with a different MPG. And it would always be in flux because gasoline and electricity costs change. Never mind that some folk would get evening rates, some don't, and others may have solar panels on their roofs.

My brother, on the other hand, is a mechanical engineer and a stickler for this kind of thing. He'd probably want to put the EV on the EPA driving cycle until it uses up 33.558kW and then note the mileage. Simple.

Simple, but not good enough for environmentalists, economists, and policy makers. There is an energy cost to harnessing energy, so we have to look at the well to wheel calculation that Tesla did early on. That's probably the most accurate - but the formulas vary according to who writes them. Personally, I'd like to know what the X-Prize spreadsheet reveals about the Roadster. But the government sets the standards when it publishes papers written by committees and special interest groups, so that's what we get stuck with.

Despite the whining about getting stuck with the EPA numbers, I bet Tesla was overjoyed with the 256 MPGe figure.

[pgwoosley]

Tesla might want to footnote the MPG figure with an explanation that the number is computed as required by EPA. This would help Tesla's credibility.

[DaveD]

Tesla might want to footnote the MPG figure with an explanation that the number is computed as required by EPA. This would help Tesla's credibility.

This is the text that I'm seeing at the bottom of the TeslaMotors.com site:

"* Range is based on our most recent testing with a Validation Prototype car at an EPA-certified location in February 2008. EPA range is subject to change pending future testing. Actual range will vary with driving style and conditions. Conversion from electric consumption to gallons of gasoline equivalent is calculated using the Department of Energy equivalence factor documented in the Code of Federal Regulations, Section 10, Part 474. "

In your opinion, is this adequate? If not, how would you like to see it worded?

[pgwoosley]

Suggested rewording:

"Manufacturers are required to convert from electric consumption to gallons of gasoline equivalent using the Department of Energy equivalence factor specified in the Code of Federal Regulations, Section 10, Part 474, and Tesla has done so. "

[vfx]

Suggested rewording:

"Manufacturers are required to convert from electric consumption to gallons of gasoline equivalent using the Department of Energy equivalence factor specified in the Code of Federal Regulations, Section 10, Part 474, and Tesla has done so. "

How 'bout

The EPA requires manufacturers to display electric consumption converted to an equivalent in burned gallons of gasoline using the Department of Energy's equivalence factor specified in the Code of Federal Regulations, Section 10, Part 474.

[doug]

Extended Interview: Tesla Motors Chairman Elon Musk | Online NewsHour | June 25, 2008 | PBS (http://www.pbs.org/newshour/bb/science/jan-june08/musk_06-25.html)

ELON MUSK: ... I mean the well-to-wheel efficiency of this car, it uses half the energy and creates less than half the CO2 per mile of a Prius when doing the full well-to-wheel calculation. So if you were to take a gallon of oil, and use that to generate electricity, and take the transmission losses and charging losses and say "well how many miles can the car go?" Or you take that same gallon of oil and you refine it, send the gasoline to a gas station, pulled up a car and drove that car, that's how you do the [...] so it's the same energy source, it's a full apples-to-apples comparison. We get about 135 miles per gallon equivalent, so compare that, that's more than twice what a Prius is.

[pgwoosley]

How 'bout

The EPA requires manufacturers to display electric consumption converted to an equivalent in burned gallons of gasoline using the Department of Energy's equivalence factor specified in the Code of Federal Regulations, Section 10, Part 474.

Sounds good.

[stopcrazypp]

Extended Interview: Tesla Motors Chairman Elon Musk | Online NewsHour | June 25, 2008 | PBS (http://www.pbs.org/newshour/bb/science/jan-june08/musk_06-25.html)
"creates less than half the CO2 per mile of a Prius when doing the full well-to-wheel calculation...We get about 135 miles per gallon equivalent, so compare that, that's more than twice what a Prius is."


I'm not sure about the CO2 per mile, but isn't the 135 miles per gallon equivalent the same PLUG-to-wheel figure originally quoted on the website. That was never a WELL-to-wheel calculation in my knowledge.

Edit:
Scratch what I said below about Ohmexcited's page, I've mistaken "gas-fired plant" to be gasoline-fired plant. So it's still unsure how the CO2 compares if gasoline was used in a powerplant to make electricity to power the Roadster vs. the Prius.

But thanks to Ohmexcited's page (a member here)
An Investigation of the Electric Vehicle's Impact on CO2 Emissions (http://ohmexcited.googlepages.com/CO2.htm)
at least the claim that a Tesla Roadster running on a gasoline fired plant emits about half the CO2 as a prius is right (though it might be older efficiency data on the Tesla).

[doug]

Sorry, I posted that quote without any comment. Yeah I wanted to point out that I thought 135 MPGe was calculated from the amount of energy contained in a gallon of gas, and not the energy required to refine and transport (etc.) it. Where as the discussion Elon goes through is a Well-to-wheel comparison. My question is does that comparison alone justify the new 256 "MPGe" (i.e. the oil was used to make electricity), or is there even more fudging to it.

[stopcrazypp]

Sorry, I posted that quote without any comment. Yeah I wanted to point out that I thought 135 MPGe was calculated from the amount of energy contained in a gallon of gas, and not the energy required to refine and transport (etc.) it. Where as the discussion Elon goes through is a Well-to-wheel comparison. My question is does that comparison alone justify the new 256 "MPGe" (i.e. the oil was used to make electricity), or is there even more fudging to it.

You are right, 135 MPGe was calculated by directly converting the energy usage from PLUG-to-wheel using the amount of energy contained in a gallon of gas.

The 256 "MPGe" number includes a 6.67x incentive factor designed to boost alternatively fueled vehicles (it's not unique to EVs).

If it were not for the incentive factor, the Tesla would get 38.4 MPGe (fuel-to-wheel, where the fuel has already arrived at the powerplant and is ready for use; note here the "fuel" just refers to fossil fuels, since the numbers involve the average efficiency of US fossil fuel plants, not gasoline/petroleum specifically) as I mentioned before. Without the dividing by "Petroleum refining and distribution efficiency", it would be 31.9MPGe (this should be well-to-wheel).

So you can see it is a little of misleading to describe the 135MPGe number as an "apples-to-apples" comparison to Prius efficiency, since if gasoline was used to make electricity, by the time it gets to the wheels of the Tesla Roadster it would likely be around 38.4MPGe, b/c of losses from the powerplant and transmission.

Reading the public comments section of the DOE document, people argue for the incentive factor to be higher for EVs, or argue for nuclear, hydro, & renewables to be counted as 100% efficient to boost the numbers, so the it isn't as high as it could have been. Either way, the incentive factor makes the 256MPGe pretty much useless for the consumer, it turns into just a number for the calculating CAFE numbers (the quote from Darryl that MDR gave actually mentioned this so at least he was honest here). Again, it sounds like the number is madated by the EPA, so I'm not sure if Tesla has the freedom to not use that number.

[vfx]

Sounds good.

I just wanted to used the word "burned" :)

[Hunter]

Wow. I'm continually impressed by how many people seem to care about this. Let me ask the most basic question: "why should we be comparing grid electricity to gasoline on a straight-up energy content basis anyway?"

The sources of energy are so different that comparing them in this way tells you absolutely nothing you care about. It doesn't tell you anything about the relative driving cost, which is by far the most important factor. It doesn't tell you anything about relative pollution, future resource availability, scarcity, or anything else. Other than simple academic curiosity, what's the point?

When you look at it that way, it's hard to justify *not* inflating mpg numbers on EVs. The energy is cheaper, cleaner, domestically produced, and available from many sources that will never run out. If you're going to make "mpg" into an all-inclusive efficiency rating for vehicles (something I think is silly in itself) then ignoring all these factors makes the metric less valuable, not more.

Personally, I think they should change the universal metric. Total operating cost per mile seems like the obvious choice. Make it over 100k or 200k miles (or better, the average vehicle lifespan) so you get in battery replacement and all the oil changes and ICE maintenance...and of course update it every model year with the projected average fuel costs over an average vehicle lifespan. This would be far better suited for the main usefulness of the current ratings (cost comparison). To cover the other bases they could add a pollution per mile index and the actual efficiency...in mpg for ICE cars and Whr/mile for EV's. No sense in converting, since you already have fuel-neutral cost/pollution metrics, and since you pay for Whr (not gallons) on your electric bill.

[stopcrazypp]

It doesn't tell you anything about relative pollution, future resource availability, scarcity, or anything else.

Personally, I think they should change the universal metric. Total operating cost per mile seems like the obvious choice. Make it over 100k or 200k miles (or better, the average vehicle lifespan) so you get in battery replacement and all the oil changes and ICE maintenance...and of course update it every model year with the projected average fuel costs over an average vehicle lifespan. This would be far better suited for the main usefulness of the current ratings (cost comparison). To cover the other bases they could add a pollution per mile index and the actual efficiency...in mpg for ICE cars and Whr/mile for EV's. No sense in converting, since you already have fuel-neutral cost/pollution metrics, and since you pay for Whr (not gallons) on your electric bill.

I think the uninflated MPGe does tell you a rough estimate of the relative pollution. Judging by Ohmexcited's numbers the 38.4MPGe of the Tesla translates to roughly .598 lbs/mi of CO2 on the average US grid, again using the EV-1 numbers since they are closer to the 321Wh/mi given by Tesla. The Corolla with 36mpg gets 0.674lbs/mi. It gives you a ball park figure in what to expect in terms of CO2 (on the average US grid, again Ohmexcited didn't have any numbers on petroleum-fired powerplants specifically).

On the cost side, you'd be surprised how close the plug-to-wheel MPGe is to the actual gasoline cost. I posted this on a recent discussion on the VW plug-in Golf.
"If you round up the latest average from the EIA (DOE) 10.2 cents/kWh for Jan 08 or 10.64 total average for 2007 to 11 cents/kWh you get $3.71, which is cheaper than the current US average of $4.07 for gasoline.
[www.eia.doe.gov] (http://www.eia.doe.gov/cneaf/electricity/epm/table5_3.html)
[tonto.eia.doe.gov] (http://tonto.eia.doe.gov/dnav/pet/pet_pri_gnd_a_epmr_pte_cpgal_w.htm)"

This is using the 33705Wh/gal figure: 11cents/kWh * 33.705kWh/gal = $3.71/gal.
Since the plug-to-wheel efficiency number is calculated using the 33.705kWh/gal figure, it directly correlates, so a 135MPGe (plug-to-wheel) Tesla would cost around the same to fuel as a 135mpg gasoline car.

But I do agree on the point about the operating cost per mile being a good metric, but I think the problem with that is that electricity cost varies so much for different areas and households, like for example in one of the threads there was a story of a person who had 2 EVs and it pushed his usage to more than 3x over baseline (so the electricity 3x over baseline came at roughly 3x the cost), which drastically raised his electric bill, unlike gasoline where there is no "baseline". In that sense, operating cost per mile really is about as reliable as the MPGe figures: it gives you a ball park figure.

I see MPGe as a kind of stepping stone, it helps show the relative efficiency of various fuel technologies, which aids in explaining to laypeople what the big deal is about these cars (efficiency-wise, not cost) at least until they get used to a new metric. (It also is very useful in internet arguments about which alternative fuel is better or how much better or worst it is than conventional gasoline cars). In terms of practicality, I think Wh/mi is without a doubt the best efficiency figure for EVs, you can figure out all the costs, pollution, etc., given this figure.

[Hunter]

stopcrazypp,

You've apparently been doing some real "fuzzy math" in this thread. It leads to this quote being very, very bogus:


I think the uninflated MPGe does tell you a rough estimate of the relative pollution. Judging by Ohmexcited's numbers the 38.4MPGe of the Tesla translates to roughly .598 lbs/mi of CO2 on the average US grid, again using the EV-1 numbers since they are closer to the 321Wh/mi given by Tesla. The Corolla with 36mpg gets 0.674lbs/mi.

First off, where did you get this 321Whr/mi number? The pack is 53kWhr. It goes 221 miles. Divide: 239.8Whr/mi. Let's use the Volt numbers, based on 233Whr/mi, leading to .373lb/mi; a far cry from your number.

The bigger problem is this silly conversion factor you've come up with. Let's start with the absurdity of basing your numbers on a hypothetical gasoline-powered electrical plant. Since no U.S. grid power is provided that way, how is this relevant? Seriously...the whole point of EVs is getting away from the inherent inefficiency and scarcity of gas! But the more important problem (that is, the one does the most to make your number so horribly misrepresentative) is that you have gone and changed the break between pump-to-wheel and well-to-wheel in an incredibly unfair way. The break should *not* be "when the fuel gets burned" but rather "when the energy gets into the car." That is, inefficiencies that happen before the customer gets the energy don't count towards pump-to-wheel numbers. This is really obvious; I'm just over here scratching my head trying to figure out what on Earth would make someone decide otherwise. I guess because you are trying to figure out what would happen in the unlikely and absurd event that someone decided to power EVs with gasoline in a power plant. Anyway, that's not the way it's done. You either compare the whole cycle (well-to-wheel) or you compare pump-to-wheel vs. plug-to-wheel.

[doug]

"Corporate Average Fuel Economy Figure for Tesla Motors: 244.0 Miles Per Gallon" Green Car Advisor (http://blogs.edmunds.com/greencaradvisor/2008/07/corporate-average-fuel-economy-figure-for-tesla-motors-2440-miles-per-gallon.html)


The Automotive News reported today that Tesla Motors, the fledgling California electric-car maker, received a 2008 corporate average fuel economy rating of 244.0 miles per gallon.

[vfx]

Great news for Tesla and for them trading the credits.

"The latest government fuel economy report says 2008-model cars and trucks sold in the United States will average 26.8 mpg, up only slightly from 26.6 mpg in 2007.

Doesn't the Tesla screw up this data? Does one (or soon 3,4 full Electric cars added to this list make the total look like all the car makers are doing better than they really are --by not doing anything?

Shouldn't there be a separate list or EVs (or partial Evs)?

[doug]

The number of EVs is still a drop in the bucket. So I don't think it would have much of an affect on the average.
Err... that's assuming they calculate the average in a sensible way. The average should be weighted by number of vehicles sold (or estimated to be sold). Whether it is or not, I don't know.

[TEG]

Does one (or soon 3,4 full Electric cars added to this list make the total look like all the car makers are doing better than they really are --by not doing anything?
Shouldn't there be a separate list or EVs (a partial Evs)?

How would they classify the Volt? If they rate it as hundreds of MPG it makes it easier for GM to meet their CAFE targets. Strong encouragement to make some, but then they end up offsetting multiple hummers per volt sold. Inflated MPGe numbers sound like a mixed bag.

[tomsax]

Inflated MPGe numbers sound like a mixed bag.

It's even worse than you'd expect. The 256 MPG number that Tesla now has on their home page is based on the EPA-mandated formula that converts kwh to gallons of gas using a conversion factor that's more than twice the accepted value based on the actual energy content of a gallon of gas. That's why the MPG number on Tesla's site more than doubled from the original value of 135 MPG. It's not that the Roadster got more efficient, the EPA just requires EV producers to ignore physics when doing the MPG-equivalent calculation.

So, yeah, the auto industry apparently got the laws and regulations written to give them twice the CAFE benefit they reasonably should get for producing electric vehicles.

[Joseph]

What is very strange is that Tesla Motors was given a CAFE of 244 mpg. How is that possible if their (only) car is rated 256 mpg?

[TEG]

It's even worse than you'd expect. The 256 MPG number that Tesla now has on their home page...

Another downside is that naysayers can use it as a point of contention saying that the EVs have "overinflated" claims. They can gripe about the disparity and blame the EV makers, not the EPA.

[malcolm]

I think that in their own long-term interests, Tesla should stick with their own figure. What's the worst that can happen? Get sued? Again?

The publicity would draw attention to the innacuracy of these calculations whilst promoting Tesla as a name to trust.

[WarpedOne]

I think that in their own long-term interests, Tesla should stick with their own figure.

Actually they should only state the official number when and where they are mandated to so and not forget to add it is EPA standard. MPG will sooner or later go the way of MIPS (Meaningless Indication of Processor Speed).

When talking about efficiency they should use outlet-kWh/mile and let public get a grip on new terms. Electric energy just can't be measured in gallons no matter how hard you try.

[vfx]

I would consider publishing both calculations. With brief descriptions of each.

I also like not stating any relationship between gas and electricity. It's a lame comparison.

[doug]

Cranking the Volt to 100 M.P.G. - NYTimes.com (http://www.nytimes.com/2008/11/16/automobiles/16STICKER.html?_r=1&oref=slogin)


The Tesla Roadster, an all-electric sports car that is now being delivered to early customers, is an interesting example of this process. Because the Tesla never consumes petroleum while driving, the E.P.A.-required window sticker lists the energy consumed in kilowatt-hours of electricity. Translating the Roadster’s numbers — 32 kilowatt hours per 100 miles in town and 33 on the highway — to more familiar units using a textbook conversion factor yields impressive ratings of 105 m.p.g. in the city and 102 on the highway. But applying the adjustment factor devised by the Energy Department, which takes into account not only energy content but also such considerations as scarcity of the fuel and production and distribution efficiency, yields far more impressive mileage figures: 256 m.p.g. in the city and 249 on the highway.

In the electric-car realm, the prevailing attitude seems to be the more the merrier, in part because of provisions in the government’s Corporate Average Fuel Economy rules, which let automakers earn credits for exceeding the minimum requirements. While mileage credits cannot yet be swapped company to company, Tesla Motors (http://topics.nytimes.com/top/news/business/companies/tesla_motors/index.html?inline=nyt-org) hopes that will change, eventually permitting it to sell mileage credits to brands burdened with gas-guzzling models.

[vfx]

The other day I was over at Fuel Economy dot Gov looking up the "gas mileage" of the Roadster. I wanted to see what was official -if anything.

The Roadster was not even there. Since it was easy I dropped a line to them.


Sent: Monday, April 20, 2009 9:01 PM
To: FuelEconomy
Subject: Please include this car.
Please include the Tesla Roadster as a currently available electric car.
Details here:
Tesla Motors (http://www.teslamotors.com)
Being a government agency I thought nothing would ever come from it. I was surprised to have this full throated answer in my box this morning.


Dear Mr. (vfx)

Thank you for your email. We had been anticipating data for the Tesla Roadster for more than a year but the last word we received is that the data would not be coming. At one time (back in 2008) Tesla certified their roadster with the EPA however, before the data were released to the public, Tesla made changes to the roadster and has since decided not to certify their vehicle with the EPA - at least for now. Cars produced in a low enough volume are not required to be certified so it appears for now that Tesla has chosen the low volume route. If Tesla certifies a vehicle with the EPA and approves release of that data, we will be more than happy to post it on our website. We thank you for your interest in our website and for taking the time to contact us.

Sincerely,

Fuel Economy (http://www.fueleconomy.gov)

Someone blogged about the 0-60 times now actually 4.1 not 3.9, this might be related.

[malcolm]

Someone blogged about the 0-60 times now actually 4.1 not 3.9, this might be related.

I thought it was because Tesla was unhappy with what it felt were over-exaggerated equivalent mileage figures.

Tesla's own 135mpg-equivalent jumped to 256 using the EPA's way of calculating.

Tesla now prefers "244 miles per charge"

I think they're waiting for someone to sort out the mpg mess - which is likely to become more confusing as REEV and PHEV manufacturers compete.

[doug]

At this point, I would think they'd want the EPA numbers to reflect their drivetrain "version 2" which doesn't come out till June.





.

[TEG]

Fueleconomy.gov has a fair amount of info on EVs as part of their web site:

Extreme MPG (http://www.fueleconomy.gov/feg/mostEfficient.shtml)
Electric Vehicles (EVs) (http://www.fueleconomy.gov/feg/evtech.shtml)

They mention the Roadster in their 2009 Fuel Economy Guide (http://www.fueleconomy.gov/feg/FEG2009.pdf):

...You can calculate the fuel cost (in dollars) of driving your electric vehicle for a year by multiplying the energy consumption for the vehicle (in kilowatt-hours/100 miles) by your local electricity rate (in dollars per kilowatt-hour), multiplying that by the annual miles the vehicle will be driven, and dividing by 100.

Tesla Roadster
Battery - Motor - City/Hwy - Fuel - Range
Lithium-Ion - 185kW AC Induction - TBD - Electricity Only - TBDSo they list the MPGe and range as "TBD".

[Serge]

They mention the Roadster in their 2009 Fuel Economy Guide (http://www.fueleconomy.gov/feg/FEG2009.pdf):

2010 Fuel Economy guide has now been released (http://green.autoblog.com/2009/10/16/feds-release-2010-fuel-economy-guide-prius-still-most-miserly/1#c22385454) and Tesla Roadster is no longer mentioned. Neither is Tesla listed as make. (http://www.fueleconomy.gov/feg/bymanu.htm)