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2012 Tesla Model S: Would YOU Drive It At Just 55 MPH?

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We've had a ride in a prototype 2012 Tesla Model S electric luxury sport sedan, and it was impressive.

The car was smooth, quiet, and relatively fast at speeds up to 95 mph on the test track surrounding Tesla's assembly plant in Fremont, Cailfornia.

Intrepid test driver (and Lotus racer) Joe Nuxoll didn't take his foot off the accelerator at 55 mph, and neither will buyers of the first Model S cars--which are scheduled to roll off the lines this summer.

Which is why we're a bit concerned that the ranges announced by Tesla for the Model S--160 miles for the $57,400 model, 230 miles for the $67,400 version, and 300 miles for the $77,400 trim level--are derived from at an average speed of just 55 mph.

That's according to Tesla CEO Elon Musk, who said at the Geneva Motor Show earlier this week--as noted by our reporter Antony Ingram at the show--that the company's range data assumed "an average speed of 55 mph."

80 mph on I-5

Many of the early Model S sedans will be sold in California, and Tesla has made a point out saying it plans to install a "SuperCharger" network of ultra-fast DC fast charging stations along the route between San Francisco and Los Angeles.

That would allow Model S drivers whose cars are fitted with fast-charging capability to refill much of their pack in less than an hour, pausing for a meal or a scan of their digital devices while the car recharges.

But the main route between the two California cities is Interstate 5, where almost no one drives 55 mph--or even complies with the speed limit.

On the long straight stretches through the Central Valley, most traffic moves at 75 to 80 mph. And we see no reason why Tesla's weatlhy, accomplished buyers wouldn't do the same.

Uncrunched numbers

We reached out to Tesla, asking the company to provide us with the ranges of their various models at the more likely intercity speed of 75 mph.

2012 Tesla Model S Charging Connector

2012 Tesla Model S Charging Connector

Enlarge Photo

Spokesperson Khobi Brooklyn wrote back, "We haven't crunched those numbers yet," and didn't respond to our subsequent request that Tesla do so.

We worry about this because Nissan quoted 100 miles for the Leaf range before launch, then ended up with an EPA rating of 73 miles--and took heat for it. Similarly, GM quoted 40 miles as the Chevy Volt's electric range, only to receive an EPA rating of 35 miles.

Sure, both companies prefixed those numbers with "up to"--but most people see only the number, not the qualifier.

Will Tesla be proactive?

We hope Tesla gets out in front on this one. EPA ratings of 120 miles, 173 miles, and 225 miles for its "160-, 230-, and 300-mile" models wouldn't help the Model S or electric cars in general.

But perhaps EPA ratings for the three Model S versions will come close to the electric ranges that the company has been quoting.

Even if that proves to be the case, Tesla needs to communicate very clearly to its buyers that if they drive fast a lot, their range will fall.

Aerodynamic drag, starting around 40 mph, increases the amount of energy required to move a car through air resistance on an exponential--not linear--basis.

That is, the energy needed to keep a car moving at 80 mph is not double that required at 40 mph, but closer to the square of the increase.

We'll let you know if we hear anything further from Tesla.

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Comments (44)
  1. Yup! Driving at 80 mph, instead of 55 mph, will almost halve the range...on any vehicle. That doesn't slow down the drivers around here. They just bitch about big oil, an g'mint conspiracies.
     
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  2. @Warren: That's true, but I suspect high speeds are more damaging to electric-car range than they are for gasoline cars. The average difference in EPA city v highway ratings on a gas car is 20 to 30 percent, but talk to an EV owner and s/he'll tell you that a steady 70 mph cuts half or more out of the range available at 30 mph.
     
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  3. Might be an exaggeration of the problem. Here is some data (not sure of the quality).
    55 mph 4.3 miles/kwh (103 miles @24kwh)
    75 mph 3.0 miles/kwh (72 miles @24kwh)
    so range at 75mph is 70% of range at 55 mph.
    http://www.mynissanleaf.com/viewtopic.php?p=101293
     
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  4. Tesla can not change the laws of physics. The Lotus Elise was, essentially, a hypercar...small, light, aerodynamic...like the EV1. When you start building electric cars like the cars most people drive, they get lousy mileage, like most cars. Lithium batteries are tens of times the weight of equivalent gas. To reduce the load of batteries required, to get acceptable price and performance, requires building a very efficient car. Sports car buyers will want a car like this, not rich soccer moms.
     
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  5. Excellent article. We have our reservation in for the S Model w/ big battery. It's clear to a lot of us in the queue, I'm sure, that one would have to baby the go-pedal to go 300 miles. I'd always assumed that if I got hold of the right person at Tesla I'd learn the range at normal freeway speeds. Is it possible that nobody there knows the answer? I doubt it. Could be a corporate lie that you heard.
    I could live with 225 at 75. Most of our driving, even on overnight weekend trips,will be on two-lane country roads. Perhaps there, range will be close to 300. We could easily make Mendocino from the Bay Area where we live. Just take Hwy 1 the whole way - slow and easy. But I'd sure like to know the real range. We also visit SoCal a lot.
     
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  6. Sorry ...

    One correction:
    The EPA EV miles for the Volt is NOT 32 miles but 35 miles.

    Also, when the EPA numbers are out for a «normal» ICE car, I'm sure that it's not based on a speed of 75-80 miles per hour !!

    If my memory is correct, it's based on a complete trip with a mix of city / highway) and always respecting the posted speed limit.

    So if you buy an ICE car, and then you drive it at 80 miles per hour, the owner will NOT complain when he realize that his MPG rating is lower than the EPA sticker ?? Also his range with a gas thank would be lower right (by at least 15-20%).

    But because it's en EV car the owner would complain?

    What I like about Tesla, compared to the other makers, is that they clearly specify 55 mph.
     
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  7. On most roads the speed limit is under 55 anyway. So the only question this article brings up is what will highway performance be like. Next!!
     
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  8. @CDspeed: Well, sure, numerically you're right when you say "most roads". But the long range of the Model S, especially the top-end models, is going to invite freeway driving--and Tesla contributes to that by openly discussing their plans to enable such trips between city pairs like SF-LA. So it's a valid question to raise, in our judgment
     
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  9. It is a good question I'd like to know the answer myself, I have family that I visit that takes three and a half hours to get to. And although I try to drive sensibly my led foot acts up and before I know it I'm doing 85 in a 65 mph zone. But I'm sure our questions will be answered sometime this year.
     
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  10. Keep in mind that the 55 mph is an average, which will include city driving and highway driving, I expect if you just drive in the city, you'll get more than the expected range as electric drive trains excel at stop and go traffic.

    That being said, the comparisons to the leaf and volt are not the correct comparison. Instead, the appropriate range quote to real world comparison needs to be with the Tesla roadster. After all, the same company makes it.
     
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  11. Somebody on the teslamotorclub site posted this pictures from a Tesla display where they had an interactive range calculator. There has been talk that Tesla needs to put this on their website for potential customers to play with, but that does not appear to have happened. So Tesla has crunched the numbers.

    http://zooi.widodh.nl/ev/tesla/model-s/range-cost-calc/

    There is an image with range calculated at 65 MPH (and the temp and other factors are included). It is image IMG_5225_2.jpg
     
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  12. That's very useful info to see. Thanks for sharing the pics. It is odd that they haven't put that on their web page- it seems a perfect fit.
     
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  13. Thanks for posting the link to these pics...
     
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  14. A terminology nitpick: it's not energy that keeps a car moving, but power. Energy is power x time; thus a kW of power used for one hour is one kWh of energy.

    Aerodynamic drag increase with the square of the speed at all speeds. Thus aero drag at 75 mph is 86 percent greater than at 55 mph. But the power (drag x speed) required to overcome aero drag actually increases with the cube of the speed. The power required to overcome aero drag at 75 mph is 154 percent greater than at 55 mph--almost triple the power (kW) required.

    But since the 75 mph car covers a given distance in proportionally less time, the total energy used (kWh) over a given distance is only 86 percent greater. Still something to think about when you drive an electric car.
     
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  15. The roadster was rated at 240 miles by Tesla then 244 miles by the EPA (I guess). The comparison with the Leaf and the Volt is thereofre irrelevant.
     
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  16. The Tesla S is not a small two seater. It is a big sedan. Putting the Tesla name on it will not improve its efficiency. And when they produce a bulky SUV, its range will suffer even more. It doesn't matter if it has Star Wars doors.
     
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  17. So... what's your point? Tesla does not claim the Model S or X is more economical to drive than the Roadster.
     
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  18. "So if you buy an ICE car, and then you drive it at 80 miles per hour, the owner will NOT complain...range with a gas tank would be lower right (by at least 15-20%).

    But because it's an EV car the owner would complain?"

    ICE drivers complain constantly, but it doesn't change their behavior. They can go hundreds of miles on a tank. A 15-20% reduction just means they stop for coffee a little sooner, and the penalty doesn't show up until they get their monthly CC bill.

    A 15-20% range reduction on a car that goes less than 100 miles, even when fast charged, would mean a 30 minute time-out, and will definitely change behavior...or cause them to sell it!
     
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  19. It all comes down to CD as to the effect of speed increases. Tables have been prepared for the roadster, but the Model S has the lowest CD ever recorded.
     
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  20. "Model S has the lowest CD ever recorded."

    Sorry. They are claiming "best in class." That class being big, fat, luxury sedans. They match the CD of the old Honda Insight. Nowhere close to the .19 CD of the EV1.

    And, of course, CD is only half the equation. The other half being frontal area, which, for the S, is considerable more than many smaller cars.
     
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  21. 55 mph vs 70 mph. There is another solution to the range problem.
    I live in Indiana and have a Model S ordered. In Indiana where not every one drives 85 on the interstate one can drive at 60 or the high 50's without being a hazard. On my longest planned trip of 103 miles one way daily I can leave 12 minutes earlier, drive 55 and arrive at the same time as driving 70 to get there. Seems like a simple solution and time saver as an alternative to running out of battery or stopping to recharge.
     
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  22. Because the first Supercharger is on I-5, you feel entitled to get a range spec that applies to 75 mph to 80 mph? Since when does any official range spec of any electric car apply to that speed?

    For the Roadster, Tesla has posted a range graph showing the range at any speed even further than 80 mph. The've said they'll have something similar for the S, and also at the Model X reveal the showed a large-screen app where you can enter the speed, HVAC/heating use, etc, and see the corresponding range. They'll have than in each store, and later probably also on the web.

    As far as I know, no company is giving more detailed information than Tesla. In the case of the S, just not yet, as those things aren't ready yet.
     
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  23. Also the range of the Roadster is also for about @55mph, so those informed about Tesla's cars didn't really expect anything else.

    Last but not least, the webpages for the Model S "Options & Pricing" and "Features" explicitly mention @55mph, since the "options % Pricing" page was added end of 2011. So this isn't "news" at all.
     
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  24. Depending on the length of the trip you can adapt the speed you drive. If your range is cutting it close you can slow down, if you have range to spare you can speed up.
    If Tesla is successful in placing it's fast chargers... floor it!
     
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  25. No one knows at this point what the range will be at 55 MPH, but except for trips greater than say 250 miles, it won't make any difference whether you drive over 55 or not - there is more than ample range for daily driving.
     
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  26. I proved this speed kills mileage rule to myself recently. I forced myself to cruise control at 60mph on a 200+ mile interstate drive (with hills) in my 2008 5-speed 2.0 Mazda 3. I got 41 mpg in a car highway rated at 32. Not only are the aerodynamics at play, but this car also needs a 6th gear to go faster IMO -- 70 mph puts your over 3000 rpm in 5th!
     
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  27. you can drive whatever you want. i drove to Disneyland with CC set to 65. i passed a few, was passed by more than a few. so what. that is what multiple lane highways are designed to do.

    its all really simple. drive within your car's capability and range and get there or dont.
     
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  28. I am with you. I commuted on a 65 mph posted 4 lane highway and traveled only 55 mph. With the four lanes, this was not a problem and I was more relaxed when I arrived at my destination. I would not try the same thing on a 2 lane road however.
     
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  29. The higher the drive train efficiency, the more loss of range at high speeds.

    Thus it is possible to cut the range of an EV nearly in half by driving fast compared to slow, since efficiency is near 90%.

    With a gas car that wastes AT LEAST 70% of the available energy even when driving slowly, you see less range variation with high speed versus moderate driving.
     
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  30. Nice way to explain it!
     
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  31. Here is a good article on range of a Tesla Roadster;
    http://www.teslamotors.com/blog/roadster-efficiency-and-range
    AT 55 mph it had a range of 240 miles and at 75 mph the chart shows about a 165 mile range. We can make a rough guess for the Model S by scaling it up 300/240, because the Model S gets 300 miles at 55. So driving at 75 mph will give you a range of 206 miles or so.
     
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  32. Another episode in John Voelcker's "I'm skeptic of anything Tesla" series. I know, this is not an advocacy site and I do admit Tesla's range predictions are a valid point because they are wildly optimistic.Fact is that range varies dramatically with EV's depending on circumstances and a lot more so than ICE range. So what happens is that EVs are advertised closer to their best scenario range (as are ICE vehicles by the way)and and some less than realistic people are disappointed when the EPA verdict comes in. In fact Tesla already stated in it's SEC filling that EPA range could be up to 30% lower than advertised. So the 120/173/225 miles sound about right.
     
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  33. Experience from EV owners who own both Roadster and Leaf indicates that it will be as easy to achieve 300 miles with the Model S (using the largest battery pack option) as it is to achieve 85 miles with the Leaf (meaning, easier than it is to achieve 100 miles, which is the first and largest number Nissan uses on its Leaf page).
     
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  34. Speaking of driving over 55MPH. I have read articles from Tesla that they have found that only a single speed gearbox is the only type that would hold up. I have also read since then articles of new two speed gearboxes that have been built to stand up to the load of an electric motor. Matching load and speed to the correct ratio makes sense. Hope Tesla is working in this area to increase range.
     
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  35. The LEAF range data is not based on 24kWh, but instead on the available energy available at warm ambient temperatures of 21kWh. Therefore, a 55mph jaunt would generate 4.3 miles/kWh without heater or air conditioning use on a level, sea level road, and result in a range of 4.3 * 21 = 90.3 miles. At 70mph, with similar conditions, would rate 3.0 miles/kWh, or 3.0 * 21 = 63 miles of range. Tony Williams, www.LoveMyLEAF.com
     
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  36. The higher the drive train efficiency, the more loss of range at high speeds.

    I don't follow this logic. If the effeciency of the EV dropped off at speed, or if the effeciency of the ICE went up with speed I'd get. But if effeciency is a constant - I don't.
     
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  37. An ICE is even more inefficient at lower speeds... per mile.
     
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  38. Boy, would I have to change MY driving habits...this is disappointing news.
     
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  39. Do you drive an EV now?
     
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  40. Tesla has published that information for the roadster here:

    http://www.teslamotors.com/blog/roadster-efficiency-and-range

    The roadster gets about 240 miles at 55mph, and about 150 miles at 80mph. Model S is more aerodynamic so it should do better, air drag doubles from 55 to 80 on roadster.

    Electrics are different than gas cars. As a gas car goes faster, it uses more power, but its specific fuel consumption (gal/hp) gets better since gas engines are more efficient at higher loads. That makes the drop off more gradual as you go faster. Gas cars get much worse in the city, especially stop and go. The EPA city cycle has lots of stop and go with very low acceleration rates, so I expect Tesla to at least make their number for EPA range.
     
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  41. Also, Tesla is rumored to be offering Aero wheels, which add 20 miles to the 300 mile range. They should add more range as a percentage at higher speeds.
     
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  42. This is silly as everyone has short memories and forget easily but the Bugatti Veyron, a fantastic technology super car that goes faster than 250 miles an hour and is I think the fastest sports car in America, has as its weakness that at it fantastic speed it can only travel for 10 minutes before running out gasoline, gasoline in short supply so that china and Japan are at each others throats to get the last drips there. So to have a car magazine writer to drive the Veyron at top speed they would need to stop for quickly disappearing gasoline 6 times between LA and that gambling mecca of America, LV,a drive of only 200 miles or so.
     
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  43. My friend has the Tesla S. He has gone 307 miles no problem at highway speed. He may take city streets that are slower and get 300+
     
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  44. Do fuel-powered cars quote their range at 55mph? NO! When a car maker says 600 miles for a diesel suv, it is on the highway, and the consumer would be depressed to find it was more like 400 miles.
     
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