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Model S EPA rating 89 MPGe

Car and driver just published this report. I wonder how this equates to the 65 kWh and 40 kWh versions? Can't wait for the test drive!

sorry for the typo that is 89 MPGe

Yes, that number was mentioned in the Q1 2012 Earnings Call.

"As far as the EPA fuel economy rating, we’re expecting it to be at least or in fact initially it will be 89 MPGe.

Although, where we think we might be able to improve that with some efficiency improvements at the charter level because it’s measuring the AC watt-hours and so we think that, we don’t promise anything but we think there is a little room for improvement there. But the current sort of official rating is 89 MPGe."

Took a while to find that article; it's brand new:

The associated table is quite interesting:

So for less then double the price of the others you get almost 3 times the range and 3 times the horsepower and 3 times the beauty and 8 times the fun factor. My figures sound about right to you? ;)

What I see is once again they mention the price of the largest battery instead of the base 40KWh which is 57K for almost twice the mileage and power.

They ar trying to say the car is unaffordable :-(


Well, they can't test what doesn't exist yet!

I assume the version mentioned in that article is non-performance version? If so, what would be the horsepower on the performance?


As originator of the thread you can edit that 80 mpg error if you wish; hover your mouse pointer over the upper left Tesla logo and the clickable option will appear.

Can someone explain MPGe? I did a quick online search and found that it is calculated by assuming 1 gallon of gasoline = 33.7 kWh.
Looking at the numbers, the Leaf and the Volt are less efficient than Model S, they use more energy per mile. But they are rated by the EPA with a higher MPGe. What gives? I did my own calculations based on 33.7kWh/gallon.

Volt Focus Leaf Tesla S
MPGe 94 104 99 89
Range 35 105 73 265
Bt(kW) 16 23 24 85
Mi/kWh 2.19 4.57 3.04 3.12
kWh/mi 0.46 0.22 0.33 0.32
my MPGe 73.7 153.9 102.5 105.1

Well, it is supposed to be the amount of electricity the car goes on 34Kwh of electricity. Maybe 33.7Kwh to be exact.

So the cars with less than 33.7Kwh get to be rated for more than the capacity of their individual batteries but the Tesla gets rated for less, because the Tesla will always hold a reserve?

It is pretty dang goofy. I call shenanigans. Get the broomsticks.


Oddly enough wikipedia goes into great detail about the whole thing. And now we get somewhere. Because the new EPA 5-cycle test includes using the heating and cooling systems plus acceleration a car that clearly excels in those aspects will have less MPGe because it uses energy to do those things. E.G. -- with less HP/potential output then the car would accelerate slower and use less electricity to get there but that has no equivalent in the 5-cycle test. A 5 second 0-60 may count against you.

Looks like carndriver chart has MPGe:s wrong. What Heinz got are right if calculated in EPA way. Looks like carndriver got their Volt and Leaf numbers from outdated EPA chart in Wiki and have used some creative calculations for Ford and Model S numbers.

Here's the official source for these numbers:

The whole EPA MPGe equivalency thing is just dumb! Why not rate an EV by kWh used per mile (city and highway) and let it go at that? I would also like to see efficiency expressed in some sort of curb weight to power consumed ratio. That would be much more meaningful to me in making comparisons between the various EVs. Since higher capacity batteries tend to add more weight to the car, you could also factor in range to that ratio.

Brian H.
thanks for the tip.

@stevenmaifert - yep! kWh/mile is calc I did based on the data above - Model S (85 kWH) comes out as the second most efficient...

How about kWh/tonne-mile? (Energy used per mile a tonne is moved)? That would factor in total mass.

Brian H - I like that! Only our government could come up with the goofy way they do it now. I wasn't around then, but when Henry Ford started producing the Model T, the gas mileage wasn't indexed to bales of hay, so why try to index EV efficiency to MPGe. Old paradigms die hard I guess.

I have a odd feeling about that EPA rating. It claims that Model S gets worse rating in city than it gets in highway unlike all other EV:s in their lists. That can't be right, so I suspect those other cars either have not been tested for city using new test, or there is error in EPA website:

Timo, good catch! I missed that one. It's really strange b/c we have always discussed how range increases at lower speeds. Notably, the Model S city rating isn't really worse than its highway rating, it's more or less the same. Still strange that there isn't a clear advantage to the city.

The only explanation that comes to my mind is the hefty weight of the Model S compared to the smaller vehicles. The Model S comes surprisingly close to the highway mileage of the smaller vehicles (10% worse), which is remarkable and must be attributed to its outstanding Cd value. Looking at it this way, it isn't surprising that in the city the Model S doesn't achieve anywhere near the same mileage as a smaller and lighter car.

I created a comparison of Model S, Leaf, Focus and Volt:

As stated before, highway mileage is very much as expected, city mileage is surprisingly low. I tried to find the curb weights to compare the numbers, but it's surprisingly hard to nail those numbers. Only on Nissan's website could I find a specification of 3385 lbs/3401 lbs depending on the options package you choose. The Model S is said to be around 3800 lbs, but official numbers from Tesla are lacking. Similarly, I could not find reliable sources for curb weights of the Focus and the Volt.

Another inconsistency: The EPA-rated range is 265 miles, and energy consumption is 38 kWh/100 miles (city or highway, regardless). As we all know, the Model S battery has a capacity of 85 kWh. 85/38 computes to 220 miles, not 265 miles. Of course, this assumes that energy consumption and range were tested by the same test cycle/test procedure, which seems to be a sensible assumption.

My mistake?


I'm assuming that the full 85kWh is not available, but held as a buffer to ensure longevity. I may be wrong, but doesn't the 85kWh represent the total battery capacity?

mklcolvin, I agree with you. 85 kWh is the specified capacity. I don't know if that means that the available capacity is lower than that, or that 85 kWh are the available capacity and the actual capacity is technically higher than that. I'd be glad if Tesla would explain it somewhere.

In any case, we can agree that the available capacity is at most 85 kWh, possibly lower. If it is in fact lower, the inconsistency I outlined above becomes even more striking.

I think the actual capacity and said 85kWh are very close to each other and like in Roadster you get the full capacity in use only with range mode. In normal mode capacity is cut off some % at both ends of the battery to increase battery life.

The experienced and proven facts thus mean that the 38kWh/100 mi. figure must be wrong. If it were true, none of the beta testers, or for that matter the 2-cycle tests, could have come anywhere near 300+ miles.

I would think that the first testing should be verification of battery capacity. Then EPA range calculations would be based on the availability of the full 85KWh and not an assumption of a lower number. After all, an ICE range is based on the full gasoline tank capacity.

a 38kWh/100 car will need 100.7 kWh battery in order to achieve 265 miles

as Volker said, a 85 kWh battery use at a rate of 38 kWh/100 miles can go to 223 miles

in order to achieve 265 miles with a 85 kWh battery, the rate have to be 32.8 kWh/100 mile.

So there is definitly something wrong in the number provided

It is not right for any of the other BEV:s either. Model S has biggest error, but others have errors too.

Would you have expected anything else Timo? All the good math techs in the US work for the NSA not

Latest curb weight number I found for the Model S: 4650 lbs. No surprise it has worse mileage in the city than a car that weighs a whopping 1000 lbs less.

The number is still not on Tesla's website, AFAICT, but it is mentioned here:

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