Engineer Questions Model S Real World Range

Since launching its Model S June 22 with much fanfare, and then quietly saying in a blog post this month around 50 cars have thus far been made, Tesla has been able to say it lacks cars to give the press for a customary evaluation.

This has not stopped several major car publications from writing brief overviews based on extremely short – as short as 10-minute – stints behind the wheel with Tesla personnel near at hand. Not surprisingly, some have criticized the startup for this which has generally bucked other industry practices as well, seeking to show it has a better way to do things than major automakers following what they say is tried and true industry practice.

In any event, we think more than a 10-minute test drive would be necessary to evaluate the battery range, if not the car. After all, why couldn’t they manage to set aside a couple cars to let testers have one for the day? A weekend? This would give a tester time to find out when the battery runs out.

As it is, we know an inferential statistician who is questioning the 300 mile all-electric range Tesla says is do-able. The EPA says it is good for 265 miles. But how much lower than this might the car go if pushed some, say with extra calls for precious electric energy during spirited driving or less than a hyper-miler’s finesse?

This gentleman’s name, for the sake of discussion, we’ll call “Joe.” He has two Masters of Science degrees from two different graduate schools, and worked as an engineer at a major component maker. For a number of reasons, he does not want his actual name to be known.

Joe, who calls himself “a believer in the promise of electric vehicles” does not distrust Tesla. He consulted the tables and graphs on the Tesla Web site and attempted to project measurements taken under ideal conditions into the real world, an art and science any automaker should be able to master.

Tesla says it tested its cars on level terrain, no wind, no AC/heat, windows rolled up, constant speed, 300 pounds aboard. Good. What happens if you turn the A/C on? What happens at differing speeds? What happens in real life?

After crunching the numbers, Joe expects that a Tesla Model S with 85-kwh battery driven at 80 mph and with A/C on, assuming less than idea driving conditions, will get about 150 miles. Then, there better be one of those Tesla Superchargers close. Even if there is, it will be an exercise in patience.

“My guesstimate would be that somewhere around an hour and twenty minutes would be required for a full recharge,” says Joe, “which includes the time required to get to and from the station from the Interstate, and also assumes no one is ahead of you at the recharge station.”

When the car is four-and-a-half years old, that 150 mile range will drop to 139 miles, says Joe while still relying on Tesla-provided data.

On the probably more common 60-kwh version of the Model S yet to be released to the public, the expected range under the less than ideal conditions drops to 114 miles, Joe deduces from Tesla data. And then you have the 40-kwh base model which could very well be in Nissan Leaf range …

Tables for the expected Model S driving range can be downloaded here. Joe also provides estimated fuel cost tables, which we did not cover here. Let’s just say that he does not buy into the 2 cents per mile claim.

Here are Joe’s research notes, in case you need his rationale behind his projections.

All of this of course will be moot once real life driving tests are available that last longer than around 10 minutes. Until then, we we don’t know if Joe’s estimate is not the more realistic picture of what to expect.


  • Van

    Depending on how much of the capacity is reserved to avoid overcharge and discharge bellow a minimum. we can assume 80% of the advertized battery will be utilized, Could be more. And if we assume 2.8 miles per kwh real world performance, we get 135 miles for the 60 Kwh version in the real world, and if we are optimistic and say it will get 3.8 miles per kwh we get 182 miles. So expect 160 real world miles in the 60 kwh version.

    If we run those same number for the 85 Kwh version we get between 190 miles and 258 miles, so expect about 225 miles of range in the 85 kwh version.

  • rewguy

    I’m sorry, but I’m not going to take advice from someone who won’t disclose their identity, even if he “has two masters degrees”.

  • david r slagle

    I have an investment of $5000 and I got a 10 min. test drive. Where do you get off thinking you deserve more of a test drive than I do when you havent even got an investment, The test vehicles are $100k and you have alot of courage thinking they should let you have one for the weekend for test. They have people waiting in line for their cars that are willing to take a $5k risk. They really are not at a point where they need help selling these cars. Last count I saw they had 12200 presales that arent met yet and probably wont be until mid 2013. At that time you may see a test drive but I’ll make a guess by then they will have at least 12000 more sales waiting to be built. I guess bottom line, get in line and buy one then you can make your test.
    PS: EPA tested it – 98mpg and 265 miles to a charge

  • Modern Marvel Fan

    I agree that Tesla’s range is on the “high” side of the estimate.

    In my experieince, my Volt will get between 4 miles to 4.5 miles per KWh in “normaL’ slow driving (no faster than 60mph) with/without A/C only impact it by at most 2 miles in range.

    But if I speed up to 75-80mph, I get between 2.5-2.8 miles per KWh. If I carry extra people and go over hills, 2.2-2.4 miles per KWh.

    Nissan Leaf is a bit better due to lower weight. But generally, 4 miles per KWh at high speed is reasonable.

    So, based on those number, a Tesla 85KWh battery should give you 210 to 280 miles in range. That is assuming no reserves and no heating.

    Heating can easily shave off 20-30% in range if NOT more…

  • Samuel H.

    Tesla’s owners have been reporting greater than projected range with some owners achieving well over 300 miles; same with some who have driven the Tesla-powered RAV4 EV almost 140 miles on a charge. Owners of the Roadster have taken coast-to-coast trips. They did it, and so can owners of the better designed and more capable Model S. The Model S’s actual range varies according to use, but worst case scenarios predictions do not help anyone.

    Real owners usually love their cars and try to get the most out of them. They are a few Chevy Volt owners who have achieved 60 miles in all-electric mode. Most owners that I know exceed their cars’ stated range. The Nissan Leaf owner that I know achieved over 120 miles on a charge once and regularly exceeds 100 miles. Roadster owners have exceeded their cars stated range, and Model S owners will. These drastic range reductions predicted for the Model S have NOT been realized by the first crop of owners. Roadster owners have proven that there will be an approx. 80% drop in battery capacity in 8 years. The battery pack can be used for many years after that, if the owner so chooses. I still has an 80% capacity. The Model S battery is much more advanced and is more forgiving of misuse.

    Predictions mean nothing. Actual range that owners are achieving should be published. Check some of Tesla’s forums. Owners are loving their cars! They do what Tesla says they will do and in some cases, more. I know that this car can take me 200 miles on a charge at interstate speeds.

    Owners trying to get to a destination will not be traveling at 80mph. If I were to take a trip in my Model S, I would pre-cool it while it’s charging. Then I would travel at 70 mph and be easy on the pedal. There will be people whipping past me wondering why this dude is going so slow. I don’t care. I’m getting to my destination gas-free, stress-free, emission-free, and silently; and for only $6 worth of electricity plus whatever the charger costs. Charge time, it is definitely prohibitive to “1000 miles in a day” type road trips.

    Here’s a 800 mile trip in a Model S.
    6 AM drive for about 3 hours. Stop for breakfast and charging 10:30 set out again. 1:00 PM stop for lunch and charge. 2:00 set out again. 4:30 charge, eat dinner, and occupy myself. 6:00 set out again. 9:00 find a hotel and charge. Viola, 800 miles in an electric car on $24 dollars worth of electricity, plus what ever the charger costs.
    Prius: 50 mpg Gas: $3.30 per gallon; 16 gallons used; $48.40 Time: 10 hours drive time at 80mph; 30 min. for lunch; 10 min. for gas stop; 20 min. bathroom breaks; ETA 5:00 PM

    BTW, Any trip that takes more than one day by car, I’m flying.

    Most houses have two or more vehicles parked in front of them. Most owners already have two or more vehicles at their disposal. Using their other vehicle for the 1% of the time spent doing roadtrips and the highly efficient electric car 99% of the time is much more reasonable than driving a gas-burner 100% of the time because of the 1% that is if cost is not the driving factor.

  • IcanhasEV

    Since the EPA rated the range at 265 miles, it seems pretty clear that Tesla was publishing a very rose-colored-glasses range estimate at 300 miles. Unless you’re a hyper-miler, I doubt you’re going to get much above that 265 miles very often. These cars are so fast, the temptation to bury that accelerator pedal is going to be hard to resist. I wonder what percentage of cars on the road actually achieve the EPA mileage ratings that they’re given? To Google!
    Edit: From what I can gather, many drivers do not achieve the fuel economy numbers that their cars are rated for. So, why are we surprised that it would be any different for an EV? I’m reminded of the saying: Your Mileage May Vary.

  • luke

    Hmm how many people can drive legally 80mph? That’s not really a real-world average speed.

    So Tesla might test under ideal conditions which would yield 200 mile range at 80mph. Sure driving uphill with headwinds and car fully loaded it it will go down but so will about any car.

    Why not ask one of the 50 new owners instead of spending this much time in trying to infer some range.

  • CapitalistOppressor

    Uphill doesn’t matter much because you regen coming down the other side. A sustained headwind is really the worst case for mileage whether you are using gas or electric. A 10mph headwind costs nearly as much energy as drive 10mph faster does, because aerodynamics at highway speeds dominates every other variable.

    But a constant headwind, sustained for hours as you transit hundreds of miles seems like a low risk issue.

  • pipcecil

    I think this article is a bit misleading. Firstly, you must understand where each number of range is coming from (yes this makes it more confusing):

    300 miles (Telsa) – Done at a CONSTANT 60 mph (actual range was 305). I don’t know if climate control was used. To me, though, its an extremely good real word test.

    265 (EPA) – EPA’s new 5 (I believe its 5) cycle test, which is more agressive on high speeds, and climate control use. A good extreme test.

    Now knowing how those numbers were generated, look at over EV’s and see their range test:

    Nissan LEAF:

    100 miles (LA4 Cycle) – an very extremely light test mostly all city driving. Extremely unrealistic

    73 (EPA) – only used the very easy 2 cycle test with no climate control and max highway was 55 mph, still not very realistic.

    So the numbers that Tesla is outputting for range is very realistic (both their 60 mph test and the EPA test) versus the numbers the Leaf, Volt, Ford Focus EV, etc. are using.

    Using a 80 mph constant test is very misleading in range, in addition its unfair since the speed to power usage of an EV is an exponential curve, a speed change from 70 to 80 is an extremely large amount of addition energy when compared to 60 to 70 or 50 to 60. Under normal driving habits that means not driving like a NASCAR driver AND not driving like a slow hypermiller, you will get 265-300 miles of range.

    Comparisons such as this you might as well say “tesla model S only gets 90 miles of range!*** ***Driving 100 mph with Heater to full. That is not fair. I am sure any regular gas car will get piddle range when you drive really fast with all the accessories going.

  • Daniel McA

    Do keep in mind that this EPA test is now a new, much more stringent test than it used to be. It now covers a lot more situations including high speeds and AC etc. (5 cycle vs 2 cycle, whatever that means! :) ). The Nissan leaf was tested using the old test and got 70 miles. If the Model S was tested using this old test Tesla said it could actually have got 320 miles! Therefore the new EPA test is already more representative of the car’s real world range

  • Mikeeeee

    The range numbers were derived from EPA tests, not TSLA directly. A 2 cycle test results in 300 miles, while a 5 cycle test results in 165 miles. Variability due to weather, wind, grade, driving style, on-board weight, etc. will alter the results accordingly. The inferential statistician should go toe-to-toe with the EPA and challenge their tests, not TSLA. BTW: My 2001 Toyota 4Runner gets around 17 MPG and varies widely depending on how it’s dirven.