Model S EPA rating 89 MPGe

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!

mbcaffe | 20 juin 2012

sorry for the typo that is 89 MPGe

Volker.Berlin | 20 juin 2012

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."

Brian H | 20 juin 2012

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

The associated table is quite interesting:

BYT | 20 juin 2012

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? ;)

My5bAby | 20 juin 2012

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 :-(


BYT | 20 juin 2012

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

kublai | 20 juin 2012

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

Brian H | 20 juin 2012


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.

Heinz | 20 juin 2012

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

Jason S | 20 juin 2012

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.

Timo | 21 juin 2012

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.

Volker.Berlin | 21 juin 2012

Here's the official source for these numbers:

stevenmaifert | 21 juin 2012

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.

mbcaffe | 21 juin 2012

Brian H.
thanks for the tip.

digitaltim | 21 juin 2012

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

Brian H | 21 juin 2012

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

stevenmaifert | 21 juin 2012

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.

Timo | 22 juin 2012

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:

Volker.Berlin | 22 juin 2012

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.

Volker.Berlin | 22 juin 2012

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.

Volker.Berlin | 22 juin 2012

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?

mklcolvin | 22 juin 2012


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?

Volker.Berlin | 22 juin 2012

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.

Timo | 22 juin 2012

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.

Brian H | 22 juin 2012

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.

foto | 22 juin 2012

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.

toto_48313 | 22 juin 2012

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

Timo | 22 juin 2012

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

Sudre_ | 22 juin 2012

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

Volker.Berlin | 22 juin 2012

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:

Nick Kordich | 22 juin 2012

I think the 38kWh/100miles represents the wall-to-wheel efficiency.

Tesla says the peak charger efficiency is 92%, so at best, when the wall socket feeds 100.7kWh to the car, no more than 92.44kWh would actually reach the battery, and some of that may be used to power the battery management system's cooling/warming the batteries in a trade-off sacrificing efficiency while plugged-in to achieve higher on-road range and battery longevity.

The Plug It In blog entry revealed a Model S won't let its battery discharge below 5%. I think that may actually be 5% of the 40kWh battery, which may account for the 'missing' 2kWh when you compare the 85kWh battery capacity we know and love with the EPA site's listing of just 83kWh. That means a delta of only 10kWh between the available capacity and the energy provided by a charger operating at peak efficiency.

Finally, the Roadster's Owners Manual says it may lose as much as 50% state-of-charge (SOC) during the first week, and then drop to 5% per week. Given the Roadster's 52kWh battery, dropping to 50% may mean that as much as 3.7kWh of electricity is lost per day if it was left unplugged, and this could be higher if the car is not as careful about efficiency when plugged-in as when it's unplugged (it might be keeping the car in a ready-to-go state having optimal battery temperature, for example).

I don't know how the range test was performed - presumably by the car being driven until it won't go any further. Given the Model S' range, it's possible this took three times as long as other EVs, and if it simulated normal driving, it might not have exceeded 100 miles per day. Even if the Model S is more efficient than the Roadster, combine this with charging not always operating at peak 92% efficiency and I think it covers the energy consumption versus battery size issues.

Volker.Berlin | 23 juin 2012

Nick, thank you very much. It would make a lot of sense for these numbers to represent wall-to-wheel efficiency, and probably they do. In that case, of course you have to charge more than the battery can store! Nice explanation.

ddruz | 23 juin 2012

Volker.Berlin, the curb weight is now on the new Specs page on the Tesla site. What's perplexing is the specs listed are for the base 40 kwh car. Wouldn't you expect that the 40 kwh car weighs less? Unless they purposely add weight to all battery packs to equalize them either the Specs page is wrong or the 85 kwh car actually weighs more!

ddruz | 23 juin 2012

Apologies. I made the above post to the wrong thread.

Timo | 23 juin 2012

4647.3 lbs is quite heavy for a car that is mostly aluminum. I wonder how much of that is battery pack and how much the rest of the car weights. I was hoping less than 4000, not over.

Around 8000 46g batteries weight 368kg which is 811 lbs, but the battery pack contains also coolant fluids and heavy duty wiring. Still, even if I count 1500 lbs for battery pack and motor it still leaves 3000+ lbs for car itself. That sounds heavy to me.

Someone with access to car scale should do a measurement after he/she gets the car.

Volker.Berlin | 23 juin 2012

Timo, I agree. Seems that battery and PEM more than outweigh (pun!) engine, gear box, drive shaft and fuel tank. Well, you have to admit, the battery has roughly 3 times the capacity of any other EV on the market. You don't get something for nothing.

For comparison, I looked up the E-class, 5-series and the Panamera: All are just below or around 4000 lbs, give or take no more than 200 lbs depending on the engine and options you choose.

Nick Kordich | 23 juin 2012

Volker, you're welcome. If this is true, however, it means the cost estimates on the charging page are off, since you're paying for 100kWh (approximately) for a full charge, not 85kWh. I think that's worth correcting, if that's actually the case.

Brian H | 24 juin 2012

I suspect all that 6-star safety reinforcement is to "blame". You don't get smash-resistance for nothing!

BTW, "weight" is not generally a verb. Just "weigh".

"Weight" can only be used in a transitive (active) sense, as in "Chicago gangsters like to weight their victims' corpses with cement overshoes before sending them swimming in Lake Michigan." (Thought you'd appreciate a vivid and timely example!)

evanstumpges | 14 août 2012

Hey all, I'm new to the forums, but have been following Tesla with great interest for a while now. It took me a while to reconcile the EPA range testing along with Tesla's stated battery pack capacity vs. the MPGe rating and associated energy consumption rating in Wh/100mi.

I think Nick Kordich hit the nail on this one and steered me in the right direction. The EPA 5 cycle MPGe tests present the vehicle's "wall-to-wheel" efficiency. The energy consumption rating in Wh/100mi is determined in the same way. According to this method, the combined EPA efficiency rating for the 85kWh Model S is 2.63mi/kWh.

When you take the EPA's tested range of 265 miles and Tesla's stated 85kWh capacity battery pack, the efficiency number looks significantly better at 3.12mi/kWh. However, this number is only considering "battery-to-wheel" efficiency and it ignores efficiency losses of both the charger's power supply and charging the lithium ion cells.

This leads me to the chart below that I created based on the data posted at the EPA's fuel economy website.


Rows in green represent data taken directly from the EPA site. Rows in green represent data that I've either calculated or taken from vehicle manufacturer's websites.

What's interesting to me is that "battery-to-wheel" efficiency of the Model S stacks up against the other vehicles in the chart much better than the "wall-to-wheel" efficiency. This naturally, leads to the question of whether Tesla's charging system is less efficient than competing manufacturers and if so, by how much? The information I've been able to find online so has not been sufficient to make accurate assertions as to the validity of this assertion. If anyone can point me to more information on this matter, I'd appreciate it. Otherwise, I'm content to wait until more people get their hands on the Model S and are able to post detailed charging efficiency data like exists for the Roadster.

Judging by the unrealistically high charging efficiencies calculated for the Leaf and Focus Electric, I feel confident that the weak link in the data is the "claimed" pack capacities by the manufacturer's. If the Focus and Leaf's actual capacity is less than claimed, this would lower their calculated charging efficiencies.

I think there are still important questions that need to be answered related to charging efficiency among electric vehicles, and if Tesla is indeed lower than the competition, hopefully they will work to improve this in the future (preferably before rolling out charging stations all over the nation).

The other thing of interest is how the EPA's charging time is not directly comparable across any of the vehicles tested because it all happens at different current draw. Unfortunately, the current draw is not listed by the EPA, making it even more confusing to the average consumer...

Brian H | 14 août 2012

You have to use HTML here, not BB Code. Here's your chart:

Brian H | 14 août 2012

You mean "Rows in green yellow represent data taken directly from the EPA site." ??

Another issue, one not mentioned here, is the fact that EPA gives lower MPGe for city than highway for the Model S. This is demonstrably and analytically false. The car is both more efficient at low speeds, and benefits from regen. Perhaps the driving protocols required use of full braking at all opportunities!

evanstumpges | 14 août 2012

Thanks for the HTML tip Brian, and I suppose the rows did turn out ore yellow than green in the chart...

The EPA's city vs. highway ratings may also be suspect here, but a few things to consider regarding this:

1. The model S is significantly heaver than other EV's in this comparison. This will negatively effect in town driving since Force=Mass*Acceleration. Both mass and acceleration will likely be greater for the Model S since it doesn't offer an "eco" mode that limits acceleration and it's got a lot more power to work with than the competition. These factors will definitely have a noticeable effect for stop and go city driving.

2. If I'm not mistaken, the aerodynamics for the Model S are better than any of the other vehicles in the comparison, which may not be a perceptible advantage for slower, in-town driving but it will become apparent at highway speeds.

Brian H | 14 août 2012

you list both EPA and calculated rows as "green" in your text.

Tesla and its beta testers both find MUCH better city mileage. And physics says lower speeds use less energy. The comparison is between Model S highway and city. The former cannot be higher. ICE engines benefit from using better rpm ranges there, but it makes little difference for an EV.

Timo | 14 août 2012

In EPA site there is chart that shows how rapid accelerations and braking is used in the city and cold environment testing (cold is basically same as city, but with cold temperatures). It uses a lot of fast accelerations and braking and almost zero maintained slow speed.

I suspect Model S suffers in this for two reasons: 1. no heavy regen used (decelerations are fast enough and regen is weak enough that that heavy car requires use of actual brakes) and 2. it can actually reach the max acceleration that test limits which means more time used in high energy consumption speeds.

I don't think this new EPA test is good for estimating real life city driving for BEV:s.

NotTarts | 14 août 2012

@evan: The total battery capacity as claimed by the manufacturer doesn't always represent the amount of usable capacity. The Volt, for example, has a 16.5kWh pack but only uses 10-11kWh, while the Nissan Leaf has a 24kWh with 20kWh of that actually being usable. We don't actually know how much of the capacity is used - and neither does the EPA, I suspect - as the manufacturer usually doesn't include that information in the specifications. Without those figures the wall-to-wheel numbers are the best estimates we have, even if they don't provide us with any information about the charging efficiencies.

toto_48313 | 15 août 2012

@evan: thank you for the very interesting post.

Regarding charging efficiencies, may it come from the fact that Tesla is using a charging approach that "protect" the battery more than the others, and then allow the cells to kept more capacity for longer time... meaning your battery capacity is deacrising less over time with a Tesla than the others.

Then I don't realy mind having 10 % efficieny less than the other if I can keep my battery pack last 20 or 30 % more. The cost of energy compare to the battery doesn't makes the difference.

evanstumpges | 15 août 2012


It could very well be that Tesla's charger is doing more than simply charging the battery to help preserve life for a longer period of time. It's something that I would be very interested to hear explained by a Tesla engineer. Based on the EPA's rated efficiencies, I think it's pretty clear that something is going on here that's more than meets the eye.

I think Tesla did a good job explaining the reason that the EPA's range rating of 265 miles is less than Tesla's claimed 300 mile range in this Blog post:

It would be nice to see another post devoted to why the Model S "wall-to-wheel" efficiency is only 84% of of its "battery-to-wheel" efficiency. If Tesla's actual battery capacity is lower than 85kWh as @nick claims above, this makes the charging efficiency worse, not better so I don't think that's the explanation. If on the other hand, Tesla is understating their battery capacity (to account for it loosing some capacity over time), this would help the charging efficiency number.

I would like to know how much of the power lost to charging efficiency is attributed to the charger itself vs. the batteries. On Wikipedia, the stated charging efficiency for li-ion batteries is 80-90% (lower than expected). I don't put much faith in these numbers, without data and graphs to back them up, but if if this is correct, then Tesla's charging power supply for the Model S is actually quite efficient. Someday, when I get my own EV I'll be able to actually measure all of this myself (can't wait for that day!)

The more I look at it, I think that the problem with my chart above is not that Tesla's charging efficiency is lower than expected, but rather that the Ford Focus and Nissan Leaf are unrealistically high. For the sake of argument, let's say that the Leaf's actual battery capacity is only 21kWh then its charging efficiency drops to 84.6%. Likewise, if the Focus's actual battery capacity is only 20.5kWh then its charging efficiency drops to 84.2%. This actually doesn't seem to be out of the question. In fact, reading some forums on the Leaf, people are reporting actual capacities lower than 24kWh capacity stated by Nissan.

It would also be interesting to hear Tesla's take on why the EPA's city driving efficiency is lower than highway. If this is clearly and demonstrably wrong as @brian states above, I should think Tesla would be working with the EPA to find out why and correct the rating if necessary...

Brian H | 16 août 2012

Timo's explanation sounds plausible. If the 5-cycle city driving consists of jack-rabbitting and hard braking, that bypasses both the low speed efficiency and the regen.

I'd personally guess (and I think I recall some observation) that average city driving is more like 140 MPGe. That would boost the "average" rating to 120 MPGe.

Brian H | 16 août 2012

Correction: to 135 MPGe.

Brian H | 16 août 2012

Dubble-duh correction: to 115 MPGe.

Edit, where art thou?