Life With 2013 Tesla Model S: 'Vampire' Thirst For Electricity At Night?

2013 Tesla Model S electric sport sedan [photo by owner David Noland]

2013 Tesla Model S electric sport sedan [photo by owner David Noland]

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A couple of weeks ago, shortly after I took delivery of my 2013 Tesla Model S, I noticed that my home electric meter seemed to be running a bit faster than normal.

I keep a close eye on my meter, but that seemed odd.

After all, the long-awaited new luxury sport sedan delivered to my house in February by Tesla Motors [NSDQ:TSLA] was simply replacing electric miles I had been driving in my Chevrolet Volt.

The two cars have about the same efficiency in winter. So it shouldn't have taken notably more power to run the Model S than the Volt, right?

I decided to try an experiment. Unplugging my 60-kilowatt-hour Model S for the night at 9 p.m., I made a note of the Rated Range display, which read 169 miles.

Next morning, the range had dropped to 153 miles.

I left the car unplugged again the next night. (Temperature was in the 20s, a bit colder than the previous night.) Range dropped  from 89 miles to 66, a loss of 23 miles. 

What was going on here? Many days, I don't drive even 23 miles.

Was the Model S actually a "vampire" that used more electrical power just sitting overnight in my driveway than it might use during a typical day's driving for me?

Two more unplugged tests confirmed the pattern: 10 miles range lost in 9 hours, then 23 miles lost over 22 hours. On average, I'd been losing roughly a mile of range for every hour the car sat unplugged.

This was different: It wasn't just a design quirk, like the good and the bad points of the Model S that I wrote about recently.

This was taking money out of my pocket and putting carbon into the atmosphere.

No State-of-Charge Readout

Unfortunately, the Tesla Model S has no direct readout of the battery state of charge (SoC). There's just an undelineated bar graph that gives you a rough idea of remaining charge.

With no direct SoC readout (either as a percentage or in actual kWh), the only way to estimate vampire losses is to extrapolate from the lost range. 

In normal driving, the Model S uses about one-third of a kilowatt-hour per mile.  My apparent 24-mile-per-day loss thus translated into about 8 kWh of electricity.  That's about a third of my total daily home electrical consumption, not counting the two electric cars.

If those mileage-loss numbers were correct, my Model S's apparent vampire losses would amount to almost 9,000 miles of driving a year. 

Delusional Owner's Manual?

My numbers were wildly contradicted by the Model S owner's manual.

"When you're not driving Model S," it purrs reassuringly, "the Battery discharges very slowly to power the onboard electronics. On average the battery discharges at a rate of 1 percent per day."

One percent? Based on my unplugged mileage-loss numbers, my battery appeared to be discharging at about 12 percent per day.

2013 Tesla Model S electric sport sedan [photo by owner David Noland]

2013 Tesla Model S electric sport sedan [photo by owner David Noland]

Enlarge Photo

Hotline to the rescue

Tesla has recently established a hotline phone number for Model S owners with problems or questions, so I decided to give it a call.

The guy on the phone quickly confirmed the vampire problem.  It seems that the "sleep mode" in the original Model S software--the basis for the owner's manual statements--had caused so many glitches in other car functions that it had been disabled.

With sleep mode missing from the current v4.2 software, he said, I could expect to lose about 8-10 miles of range per day when unplugged.

Using the rough three-to-one conversion ratio, that worked out to about 3 kWh per day.

He assured me Tesla was working  to come up with new sleep-mode software as soon as possible, but he offered no estimate of how long it might take.

Last week, Elon Musk addressed the vampire/sleep-mode issue in a meeting with Norwegian Model S buyers in Oslo. Musk promised that the new sleep mode would reduce vampire losses to a mere 0.2 percent--a miniscule 170 watt-hours--per day.

And, he said, the new sleep-mode software would be installed by the time the Model S was introduced in Norway--currently set, he said, for July.

Faulty mileage readings

But my apparent vampire losses were more than double what the hotline rep said they should be. Did I have a special problem?

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Comments (58)
  1. This is extremely interesting. The most interesting question here may be why this doesn't seem to be happening to any other electric car. For example, I have not heard that anything of this is happening to a single Volt owner. If you leave a Volt for 2 weeks, it may have lost perhaps 2% to 5% tops of its EV range, if even that. And what's with this whole thing about it being better for the battery to be cold, versus being warmed up? Isn't there one optimal temperature, and if so what it is it? (say, 50 degrees, 57, whatever) It appears there are still many unanswered questions here.

  2. Yes, I agree about the Volt. I've never noticed any vampire losses with mine. Even after sitting for 12 days while I was on a trip, it had lost virtually no charge.

    My understanding is that there are two optimal temperatures for a battery, one for running (warm) and one for storage (cold).

  3. I'm suspicious about that duality. What degree precisely is optimal for driving, and what degree precisely is optimal for storage? And what is the logic behind there being a difference at all between the two? Why would the optimal differ between storage and driving? It is not intuitive, but I'd love for engineers from multiple EV car OEMs to weigh in.

  4. The warmer temperature helps with the "peak power". A cold battery can NOT deliver the peak current requirement for most EVs. So, the warmer battery is there to make sure you can have all the performance.

    But a colder temeprature reduce "aging" process of the battery. That is why it is better to store the battery at a colder temperature for "long term" storage.

    I wouldn't call 1-2 week a "long term" storage. But there is no way the car would know.

    Maybe an option would be nice. However, that will leave the option to users who have NO idea how battery works...

  5. The Volt does not have a massive suite of computers which draw a ton of power when they are prevented from shutting down.

    This is not an "EV" issue at all. If you leave the dome lights and radio on in your gas powered car it will drain the battery. Or if you did the same thing on your Volt you would have reduced range in the morning.

    Same issue, except the losses are from the computers.

  6. That only begs the question: What do these "computers" do in the Tesla that they don't do in the Volt? What benefit do they yield in the Tesla that are somehow not performed in the Volt?

  7. Actually, the major difference is the detection and waking up of the computer.

    Tesla's the computer is constantly in a sleep mode or standby so when it sense the key, the door handles has to pop up and the car has to be ready to drive.

    Volt's computer doesn't come on until you press the power/on button on the dash. That is why it takes about 3-4 seconds for the Volt computer to do all the self check and before all the messages go away.

    I don't see why Tesla can't switch to the Volt's on/off style. It is certainly easier on the standby/sleep circuits and will save a lot more power.

    But Tesla wants to stand out and choose to be more "advanced" but it also takes on risk and potential problem.

  8. But why have the computers running when the car is parked and OFF? When my Fluence ZE is unplugged and idle it uses virtually no electricity, so why should the Tesla operate the computer when the car is idle?

  9. There is no mystery here. Tesla had a software problem with the car starting back up so they disabled the feature that reduces power draw when off. Once they get that worked out, they will enable the feature again, and the power drain will go away. This is a well known issue, discussed by Tesla, I'm not sure why the author seemed to be unaware of it.

  10. David, You mentioned the battery had to be brought to the correct temperature before charging. Did you account for that power use in your measurements? If not, that could be large portion of it.
    Hopefully Tesla gets that sleep-mode sorted soon.

  11. I don't believe the battery was warmed before charging in my case. It appeared the charging started immediately after I re-inserted the plug. According to the owner's manual, there would be a delay if the battery needed heating or cooling before charging commenced.

  12. My Sig P85 displays the message: BATTERY WARMING! when the battery is being warmed by the battery power. There is no message when it warms by the grid.

  13. Not only that but the battery charges better when it is cold, That is why the Better Place swap-stations have serious air-conditioning units to drive cold air into the discharged batteries off-loaded from the cars as they charge so the charge time is reduced

  14. Dave, You waited long enough for the car. Stop whining and drive it. Every car has it's quirks and guess what? Life is ticking by drive it or turn it in to someone that would appreciate it and drive it. I bought my Porsche Cayman USED in Dec. of 2010 and drove it until it snowed and it did. Then I drove it every day the weather was good. and still do. Enjoy it. Pretty good car ewith it's MINOR quirks don't you think? Enjoy it!!!!!!

  15. i appreciate the reporting.

  16. So in your mind he's not allowed to tell the truth about the Tesla? Perhaps you should wipe off that Tesla Kool- Aid running down your chin.

  17. In Garry's defence: Mr. Noland does tend to stress the negatives about Tesla and it's product while rarely having anything positive to say. One would expect someone who just got a great car like that to just plug it in at night so he could enjoy driving his car to the max the next day. Instead he often seems to leave it unplugged just so he can watch the range drop and gets in all sort of measuring exercises just so he can whine some more about a problem that was already well known and being sorted by the company: the sleep mode issue, apparently in a hurry to milk it to the max for its negative news value before it's sorted by the company.

  18. I agree with Jeff. I don't think the author is biased. In his first article he couldn't followed his car around town because he couldn't wait for it to be delivered. He obviously has a technical background and just wants to understand what is going on with his car.

    Don't get me wrong, I'm a huge Tesla fan. But Tesla needs for these issues to get some visibility so that they can continue improving the product.

  19. Don't know about technical background, in fact I know as much about Mr. Noland's background as any reader of this blog: nothing.

    However he is a self proclaimed early enthusiast and he writes articles about Tesla and the Model S so presumably he is well informed, yet he acts totally surprised by the sleep mode issue and lower range predictions after not plugging in during a cold night, even though countless readers of blogs like this could have told him about that, especially after "broder-gate".

    Sorry, that all feels like an act to me. Don't know why he chooses to pretend fear uncertainty and doubt about his experiences with his car (vampire losses indeed...)but like I said: I know nothing about Mr. Noland.

  20. Well, isn't it important for EV owners to know how much their cars draws in power at night? Isn't is important to know how much range it loses when it is cold and not plugged in?

    As a plugin owners, those are important questions.

  21. Mr. Noland would really be on to something if parasitic load was an until now unknown problem. As things stand it is very well known and Tesla is on the brink of solving it. Mr. Noland is just in time to report it as an issue before it isn't even an issue anymore. He won't even have to go to the shop, it's all automatic software updates.

    Criticism on real issues with the car is good. Borderline invention of problems isn't.

  22. It is good to read some "negative" experience about the Tesla. But all we ever read here are how great Tesla is. I agree with most of that praises. But that doesn't mean Tesla is perfect. It is good for future owners to know those "quirks".

    Those are EXACTLY the kind of "owner experiences" that I am looking for from Mr. Noland.

  23. Keep following Mr. Noland's reports if you are interested in the negative. So far he hasn't disappointed in that regard and I have a hunch he won't disappoint you in the future.

  24. Well, we don't need "blind" followers of the EV movement. We need real life experiences. In order for EVs to spread, the real life experiences are valuable to real world owners as well as potential owners. This is also a good area where EVs should improve on. There is NOTHING wrong with "negative" sides of Tesla being reported especially when you are trying to keep an objective view of the issue.

  25. Blind follwers like your see no evil hear no evil attitude towards your beloved GM you mean? No, that's not me, I think it's very good to report the negative if there is real problems to be reported. Writing a lengthy article suggesting the discovery of ominous "vampire losses" when Tesla is really on the brink of solving the issue seems like trying to make something out of nothing though.

  26. There are more comments in this thread
  27. Something tells me Dave being a freelance writer driving the car and not whining about will be a little too much to expect.
    Still can't believe he leaves it out in the open with a few rocks piled around it, maybe its the start of a garage!

  28. There are more comments in this thread
  29. "Send a freaking e-mail."

    The information about sleep mode being disabled is contained in the release notes, which is accessible through the touchscreen.

  30. "Overall average of the four test sessions: 4.5 kWh per day"
    Great article and stunning vehicle, and kudos to your common sense sleuth-work- It's definitely on my next vehicle radar.
    An interesting note, the Aptera IIe would drive about 50 miles on 4.5 kWh :-)

  31. I am sure Tesla is working this diligently. Please update us when the new software is installed.
    I agree that you should have a SOC gage readout option based in 100% being the 85, 60 or 40kWh battery pack. Tesla may not wan to do that because reading in their 2012 Form 10-K annual filing to SEC & investors, Tesla's battery and extended battery warranties do not include charge capacity as part of it. If loss of capacity turns up as an issue to customers, like it did with Nissan this past summer; Tesla can say too bad not cover in our warranty.

  32. Hi Mr. Noland,

    Thank you very much for all the updates on the Tesla S. Your experiences are exactly the kind of experience that I am looking for. Keep up the good work.

    You mentioned:

    "Heating or cooling starts automatically when you plug in, and charging begins when the Battery reaches the appropriate temperature"

    I have read that some owners complain that the standard 120V (1.4KW) outlet can NOT keep the Tesla S at proper temperature in the extreme cold so its battery can't be warmed up with only a 120V outlet. Is this true? Have you seen such a problem with your Tesla?

  33. My understanding is that nothing keeps the battery at any particular temperature when it sits idle in the extreme cold. There is no "proper" temperature. The battery is allowed to get as cold as the ambient temperature dictates.

    As I iunderstand the owner's manual, when the battery needs to be topped off while plugged in, which can occur after 18 hours or more, there is a minimum threshold battery temperature required for charging. If it's colder than that, the battery will be warmed before charging starts. But most of the time, it just stays cold.

    I haven't experienced this threshold temperature, so can't say whether a 120v outlet has enough juice to warm up the battery and allow charging to begin.

  34. I have to think that there is some ramp from "too cold can't charge at all must warm the pack" to "it's pretty cold, can only charge at 5 kW" to "pack warm, can charge at 90 kW".

    In the middle there the car might charge as fast as it can (which will heat up the pack on it's own) and use any spare power to heat the pack up faster.

    I bet you could monitor this by looking at the dash when charging - the miles/hour charge rate should start low and then start climbing as the pack warms up while the volts/amps reading stays constant.

  35. Have you tried at 120V? Does the pack gets any kind of charges at all during extreme cold?

    What if someone parks a Tesla S at a long term airport parking lot in the middle of winter and plugged into a 120V outlet, will it keep the car charged up at all?

  36. Many in Canada use 120V charging to "trickle-charge" and keep the battery warm. In the cold, it will only gain a mile or two an hour on 120V, so it can be left plugged in and warming a long time.

  37. I have been reading Mr. Nolan's articles for months. I believe him to be an objective journalist who calls it like he sees it. If he had a hard spot for Tesla, would he have put out a small fortune to purchase a Model S just to diss on it... I don't think so. He writes about the good and the bad. What he writes about here has been discussed ad nauseous on the Tesla forums. Model S is a phenomenal machine, but there are issues and this 'Vampire Load' one is significant. There are other issues with Model S that Mr. Noland may write about in future articles. As long as he's objective, the fan boys have no reason to gripe.

  38. The "fan boys" club will always objective b/c they are fan boys... To them, the Tesla can do no wrong. That is exactly the wrong attitude we need at this early stage of EV adoption.

    With all the quirks that Tesla has, I still love to have one. But it doesn't mean it is perfect. This is exactly where people learn about a product's strength and weakness.

  39. So, I know M'm a little late for the party here, but what was the issue with Sleep Mode in the tesla?

  40. The issues are explained in a previous article by David: Read down to "Software glitches" I have not experienced any of the problems with 4.1 reported by others, and have been telling the car to ignore installing 4.2 for over a month. I still have sleep mode and only lose 2 miles of rated range per day.

  41. David where do you leave your keys at night? are the still "talking" to the car?

  42. @David Noland
    I read that you saw the "Olso video". In that same video Elon Musk tells the audience that "sleep mode" will return before EU deliveries and will consume 0.2% per day or 0.17kWh/day.

  43. Great Story Thanks for the Info
    I noticed that in the last picture that you where charging the car outside is it normal kept outside or garaged. Would this make a difference ? I noticed in the reporters story that badged the S he parked it outside on a very cold night and the Tesla logs did show it lost a fair amount of range possibly this could be part of the problem.

  44. I wonder if the Tesla-battery-equipped Toyota RAV4 EVs have vampire issues too. Anybody know?

  45. that's where solar panels complete the equation.
    EV = zero gas fuel
    solar panels = zero utility bill
    electric car + solar panels = complete independence in fossil fuels

  46. i have a bit of trouble believing that your restarting the charge on the Tesla is a good way to determine how much power was used for various electronics daily. batteries are simply not that cut and dried.

    also, i have doubts that the overnight losses you have observed will sustain itself over time. granted, this will be VERY difficult (for me anyway) but you should try letting it sit for 3-4 days. I am relatively sure your rate of phantom power usage will drop significantly.

    another thing here is that most EV'ers have learned that your best course of action is

    1) ignore the estimated range meter
    2)get a meter that actually tracks the amount of charge in the battery. now with your range, this might not be a major issue, but in a LEAF

  47. 1) agree. Ignor the "Guess Meter" i mean range meter. 2) agree. get an accurate SOC meter at least for the Leaf.

  48. @David
    Two things are effecting your overnight energy drops. 1) the loss from systems remaining on (vs. sleep mode) & 2) lower temperatures with this time of year.

    To get a better idea of the non-temperature related measurements you should park the S at a constant temperature garage. This should be fairly constant value vs. temperature related battery management use.

    "Sleep mode" was disabled to avoid a software configuration issue as car wakes from sleep. Today's vehicles can have a 100 computer units in various subsystems. Most vehicles today are either on, or off… essentially the computers are rebooted each time vehicle is started. "Sleep Mode" is more common with PCs than cars and even with PCs it took time to realize expectations.

  49. This is the best, unbiased writeup on "vampire loads" that I have seen. It makes it clear that the issue isn't trivial and has real consequence in aggregate. I'm sure Tesla will fix this - but I hope it won't take too long. It is costing me $30/month! You can see my calculations at - not quite as bad as what you've seen (warmer weather), but really significant.

  50. It would be a good idea for Tesla to look over its software to see if they could reduce the parasitic loss of battery charge that occurs while the car is parked. I for one would hate to see losses greater than a few miles of range just for sitting 1 day. What actually needs to be running in the car vrs what can be totally shut down to conserve the battery should be addressed. Tesla has the best EV on the market by far and they should be looking at their software to look for potential energy savings on what can be shut down or sleep modes that can be put in to conserve battery charges

  51. I compared this article with my 22KwH Fluence ZE.
    Placed overnight the range indicator did not loose a single kilometer, nor did the charge indicator lose a single percent
    After an all night unplugged, plugging in did not activate the blower which always starts at the beginning of charge
    Even if the vampire mode so eloquently described was active, it would cost me nothing because better-place pays the electric bill, regardless of where plug-in or batt-swap happens. I pay the miles-charge, and thats it.
    Think about paying 30K dollars for a battery-pack that discharges incessantly every time you park. Ridiculous
    So the car is fantastic but its achilles heel is as always the battery. At Tesla you pay for it and are stuck with it. Not at BP

  52. I don't know--I think I prefer owning the battery and trusting Tesla to send me an over-the-air update to solve the drain. By contrast, what happens if Better Place goes out of business? Oops.

  53. With the tiny mileage you have each day, you'd probably be better served using a 120V charge (or amp-limiting the charging to 5-10A). That way the charging/warming will persist thru the night and you will get true readings plus a warm batt in the a.m.

  54. Good article and huge mistake by Tesla to not have learned from the bad engineering on the Roadster. Never mind that the drain was so bad it could kill the battery but just the fact that it constantly burns 100watt 24 7 is piss poor engineering.
    It is totally unnecessary to have such a drain in an EV and it kills the joy.

    As for the cold issue of the battery, that's one of the reasons I don't like batteries in the floor (exposed to cold). I want a tight block inside the car and thermally insulated such that a tiny amount of power can keep it at minimum temperature in cold weather. That way it could be ever ready even in -30c winters (unlike dumb ICE cars)
    and you don't have these surprises of vanished range, nor delay before recharging.

  55. @Dan Frederiksen: Everything is a tradeoff, but having the battery pack in the floor allows it to be a structural member in the car and gives the car a very low center of gravity. It also makes battery swapping a lot easier and doesn't take up room that could be otherwise be used for storage or passengers.


  57. Hat's off to Chevy on this one. Sometimes that build by committee thing has it's benefits. Looks like the Volt is optimal at this point in time for it's lack of Vampire losses when the car is actually off. However, I do believe that Tesla will fix the sleep mode and to Tesla's credit - will roll out the solution to the entire fleet. Chevy still has more of that old school only tell you about a SW fix if you 'need' it at the moment. I hope that watching Tesla and how it 'runs' / treats the customer, teaches an old dog some new tricks. I have seen both cars and believe them both to be awesome in slightly different ways. Still waiting on the Tesla Test ride here in Austin Texas.

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