Energy Consumption Of Various Tesla Heating Features

OCT 21 2016 BY STEVEN LOVEDAY 40

One of the few disadvantages of EVs is that they don’t create the excess heat associated with ICE vehicles. Energy from the battery must be used to produce heat when the cold weather sets in. The Tesla Model S and Model X use resistance heating (think of a space heater) to heat the cabin. Other Tesla heating features include, heated seats, defrosters, heated wipers, and heated mirrors provide protection against the cold.

tesla-heating-2

KmanAuto Uses An App Called Remote S To Measure Power Consumption

This is all part of the reason that EVs lose range in the winter, or in generally colder climates. How much power do heating features consume?

The YouTube video by Model S owner, Kman Auto, spells it all out.

Chris shows us Tesla’s SubZero Weather Package and its power impact. His breakdown is below, and thanks to Teslarati, we also have estimated range reduction by the amount of miles per hour.

Baseline (vehicle at rest but powered up): 247 Wh = .74 mph
Defroster (rear window & side mirror heaters): 285 Wh = .86 mph
Steering Wheel Heater: 95 Wh = .29 mph
Heated Wipers & Nozzles: 95Wh = .29 mph
1 Seat Heater: 57 Wh = .17 mph
2 Seat Heaters: 1cabin reached 108 F quickly33 Wh = .40 mph
3 Seat Heaters: 171 Wh = .51 mph
4 Seat Heaters: 209 Wh = .63 mph
5 Seat Heaters: 247 Wh = .74 mph
HVAC at ‘HI’ or 82F (28C): 6.4 kWh = ~18-20 mph
HVAC at 74F (23C): 342 Wh = 1.03 mph

With the 18-20 miles per hour lost with the heater on high, its much more efficient to use the heated seats to warm up, with the cabin heater warming slowly, on the lowest setting. However, since the cabin reached a whopping 108F pretty quickly, it would be crazy to run it on high for a full hour.

Source: Teslarati

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40 Comments on "Energy Consumption Of Various Tesla Heating Features"

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Just have to say that the whole MPH thing seems kind of ridiculous. I mean we don’t all drive that exact speed for an entire hour. Personally I think a kW per hour makes a lot more sense as regardless of how fast you drive the energy usage would be the same.

Still though, kinda cool.

I was confused by the units used as well. But I think they make sense if you don’t consider “mph” as velocity as we normally do but instead as “the number of miles of range lost per hour”.

I don’t think you get how the units “miles per hour” are bing used in this context. The “mph” shows the miles of range lost for each accessory for each hour of driving. It doesn’t matter how fast you drive, it matters how long you drive.

If you initially had 250 miles of range and turned on various heating accessories that added up to 10 mph and drove for 2 hours, you’d lose 20 miles of range to support the accessories. Your adjusted total range will be no more than 220 miles.

You could also do it by adding up the watts of all the accessories, multiply by the hours of expected driving, then dividing by “typical” Model S driving watt-hours per mile to get the expected range loss. The “mph” numbers just did a lot of the math for you ahead of time.

+1

the miles/hour figure does not make sense because the miles you get for each kWh is not constant. fortunately, he did give actual Wh, which is the more significant figure. i’m going to assume that what he actually measured was instantaneous watts and then he extrapolated that over 1 hour to get his “watt-hour” figure. although, as poster “chris c” noted below, if he stated that he was measuring “watts/hour”, then i would generally wonder whether he actually knows what he is doing. if not, the whole set of figures that he is reporting might be worthless.

i don’t have 27 minutes to watch the full video but the problem with the HVAC figure is that it is meaningless unless you know the exterior temperature and the interior temperature. HVAC draw is a function of the temperature difference between interior and exterior temperatures. that’s why HVAC draw is so significant in colder climates.

for me, seat heaters don’t really do me much good. when it is cold, i am wearing more clothes. where i get the greatest sensation of cold is in my hands as i generally don’t drive while wearing gloves.

So first they work hard to vent out heat from the battery, then they use the same battery for a resistive heater? There must be some optimization opportunity here

The heat from the battery is generally low grade, getting useful only on high currents. So not worth it for general use. Surprised that the Tesla has resistive heating though, not very efficient. Why not a heat pump? Would cut that load in half. (Ok, I assumes it’s a weight thing with such a large battery, but I’d love to see the calculations)

Heat pumps are great but not perfect in cars. (I know from experience with both systems in different EVs)

Heat pumps pros:
+ more efficient in mild weather (drops with lower temperature and significantly below freezing)

Heat pumps cons:
– Longer delay before first heat is delivered
– Noisy technology (not ideal for premium cars)
– Pricey
– Struggles with heat capacity in very cold situations due to dropping efficiency
– Less robust with more mechanical parts and coolants

Perhaps there is a bit of a learning curve with automotive heat pumps, but in general, hybrid and electric automotive hvac systems are superior in general since they use variable speed, semi-hermetic compressor units which are adaptable to heat pump systems. Think the ‘cold weather’ Mitsubishi home systems that have a high Coefficient of Performance (COP = EER/3.413) during quite cold weather, (certainly down to even 0 deg F), and the added complication is mainly valving. With electricity being so ‘expensive’ so to speak in an EV (to get more of it you need a bigger, heavier battery), there should be great impetus to use LESS of it for heating. If the car is going to be airconditioned in the summertime, and places like Tucson need airconditioned batteries, you have to have the hardware anyway; the added complication of the heat pump valving isn’t a superbig deal, and I’ll bet you’ll see a lot more heat pumps displacing resistance heaters once the suppliers or car manufacturers in general get more comfortable with it since its such little extra hardware to add to get a big benefit. Cars like the VOLT which currently don’t have a heat pump I can accept… Read more »

“Technical review” said:

“Heat pumps cons:

“– Struggles with heat capacity in very cold situations due to dropping efficiency”

Yeah. Heat pumps are great for energy efficiency in mildly cold weather, but in very cold weather they simply don’t put out enough heat, so you need a resistive heater.

Some EVs do have both. Why doesn’t Tesla? I don’t know.

The Prius Prime has a “vapor injected” heat pump that allows it to work more efficiently at colder temperatures than an ordinary heat pump.

Per InsideEVs:
“What’s the most often heard comment about heat pumps: ‘They don’t work when it’s cold.’ What if there was a solution? Via Toyota Japan, Toyota says they have it. It is a ‘vapor injected’ heat pump.”
http://insideevs.com/advanced-heat-pump-comes-of-age-in-the-new-prius-prime-bower/

“- new heat pump system, which is 30% more efficient than the first model (at 14 F). . .”
http://insideevs.com/first-drive-toyota-prius-prime/

Thanks for the info, sven! I hope this turns out to be as good as Toyota is suggesting.

Good to see that Toyota is, apparently, contributing to the EV revolution even though they keep dragging their feet about putting a compelling PEV (Plug-in EV) into production, and keep spouting anti-BEV propaganda when advertising their “fool cell” car.

GE is working to commercialize heat pumps developed by Xergy that use a hydrogen electrochemical compressor (ECC). These ECCs, based on hydrogen fuel cell tech, are solid state, silent, use hydrogen as the refrigerant, use about 30% less electricity than mechanical compressors, and compresses hydrogen without significantly heating it during compression (isothermic). In fact, when these ECC are used to compress hydrogen to 700 bar pressure (for fueling applications) there is no need for interstate cooling as is required for mechanical vapor compressors.

Due to their higher efficiency, these hydrogen ECCs are predicted to replace the mechanical vapor compressors used in HVAC equipment, water heaters, and refrigeration equipment.

http://www1.udel.edu/udaily/2016/mar/fuel-cell-technology-hvac-031616.html

https://www.hydrogen.energy.gov/pdfs/review12/pd048_lipp_2012_o.pdf

Haven’t read the link yet, but I’m skeptical. 30% less electricity than normal mechanical compression, and think this would have application EVERYWHERE, not just cars, which are a minor application.

The best refrigeration systems can be 30% more efficient than typical, its just that some installations can’t be bothered, or are set their ways – for instance it is much more efficient to use water from a cooling tower to cool the heads of a compressor than it is to use refrigeration gas itself, and also not use this to cool the motor since the object is to get rid of heat from the conditioned space, not add to it IN AN AIRCONDITIONER.

The object is to recover as much heat as possible of course, when a heat pump is in heating mode.

But any system that can perform a ‘compression’ without ‘doing work’ on the gas has just truly violated the second law of thermodynamics, and I’m not kidding this time. Isothermal may be one thing, but if they are talking about no heat-of-compression, I think they’re talking about some other universe.

Note to editor: had a lengthy reply here I wonder if you can fish out of the typing cache. I question the sleight of hand here calling this ‘isothermal’. The resultant compressed hydrogen (not used in refrigeration of any kind, but merely to get the 10,000 psi required for fuel cell cars via ‘simulated hydrolysis’) – obviously the electricity is going somewhere and, without violating the second law of thermodynamics (For real this time), there just has to be sensible heat. I can’t find a P-H table of hydrogen unfortunately just now. If it could, you’d be talking about a different universe, since if you released the gas it would cool – so obviously it must have gotten hotter first, unless the heat is removed while it is being compressed. If that were possible, you’d get more savings than just 30 % – thats why I say they’re not being super-rigorous here. But that Univ of Delaware link I’d be suspicious of, since trying this with refrigerants which change state is a bit difficult since you have more than just hydrogen involved. H2 itself would present a bit of a problem, since its critical temperature (the temperature above which it… Read more »
Apparantly, the electricity it going to a stack of Proton Exchange Membrane (PEM) that make up the anode, (which strips/separates the electrons from low pressure H2 and generates protons), and to a stack of PEM that make up the cathode (which draws the electrons from the anode and electrochemically drives the protons across the membrane to recombine with the electrons to form hydrogen under increasing pressure). The hydrogen is electromechanically compressed to 800 bar (or more) in a single stage. Taking the second law of thermodynamics into account, the exergy efficiency of an electrochemical hydrogen (ECH) compressor is claimed to be “70 to 80% for pressures up to 10,000 psi or 700 bars,” per the Wikipedia entry for “hydrogen compressor.” See also the Wikipedia entry for “Electrochemical hydrogen compressor.” A few companies make ECH compressors for use at H2 fueling station applications, but Xergy was the first to patent a system for use in HVAC, water heater, and refrigeration applications. Xergy filed/holds the patents and developed a prototype, but is letting big name companies license the tech to develop cost-effective products using the tech: GE, Pansonic, Samsung, Siemens, Coca-Cola, and even Unilever (which owns many ice cream brands). Details of… Read more »

Here is a video of Xergy’s founder giving a presentation on the ECH compressor tech, followed by a Q&A session (all questions after the first one are utterly useless). At 1:55 into the video is where I got the figure for 30% greater efficiency than a conventional electro-mechanical compressor.

Oh, man! He said it himself: “You have to be very clear…..If you can’t state extremely clearly why your idea should be listened to, you’ll be thrown out, and its happened to me several times.” (!!!!!!) Meanwhile here, he never explains the idea except to say he is more efficient. I’ve already stated it is possible, in stationary applications, to get 30% improvements in efficiency. Want proof? Check out any of the ‘water furnace’ products. They provide an extremely low cost heating or air conditioning source mainly because ground water is at a sweet-spot temperature wise, and this is even WITHOUT doing easy efficiency improvements such as using slow-speed open reciprocating water cooled machines that FURTHER increases in efficiency – the water furnace products use a conventional mediocre efficiency compressor. Its interesting that he says the first application of this product will be in GE’s ‘hybrid’ water heater. Interesting to me, since here, its only a heat-pump function, and in this application, YOU WANT ALL THE HEAT YOU CAN GET. In other words, if you use a mediocre efficiency compressor, it doesn’t matter since the ‘extra’ waste heat goes to heat the water anyway. All the heat into the water… Read more »

With regards to using an electrochemical hydrogen (ECH) compressor for a fueling application, Nuvera recently demonstrated one fueling a Hyundai Tuscon FCV. Nuvera sells H2 forklifts and industrial vehicles.

http://www.nuvera.com/blog/nuvera-demonstrates-electrochemical-hydrogen-compressor-for-premiere-fueling-event

ITM Power, which makes industrial-sized electrolyzers, has opened a fueling station in the UK that uses a ECH compressor made by HyET to compress H2 generated on-site. It appears that the station uses grid electricity, but ITM power has another H2 station that uses a solar array to (partly?) power its electrolyzer and yet another station that uses a wind turbine to (partly?) power its electrolyzer. However, neither the solar or wind powered station make mention of using a ECH compressor. Also, no mention is made as to whether any of these H2 stations can sell electricity back to the grid for balancing or frequency regulation.

https://www.energyvoice.com/otherenergy/94287/itm-power-completes-hydrogen-car-refuelling-project/

Well, not to oversimplify the issue here, and you’d have to talk to a physicist to determine the effectiveness of this system to compress hydrogen. The fact that it is 80% efficient is believable – at least he didn’t say it wasn’t 100% efficient, or a perpetual motion machine.

But as far as hvac or heat pump applications, there is a problem with isothermal compression. For it to happen, heat must be removed to avoid a rise in temperature.

The problem is, the gas will liquify during the process (condense). Actual compression in a real compressor is in a range between Isothermal (contant temperature), and Isentropic (no heat transferred) – in actual practice some heat is lost to the cylinder walls of the compressor, and heat is added due to wire-drawing of the valves, valve leakage, frictional loss in the refrigerant itself (since it isn’t a perfect gas), but by far the most added heat is due to the work done on the gas.

I smell a rat here:

“How evaporative cooling works:

Hot Dry air IN -> Cool refreshing air out.

What he neglects to mention is that the ‘cool refreshing air’ has more enthalpy (heat content) than the incoming hot air. Little detail.

‘Swamp Coolers’ and other products popular in the SOuthwest US work by exploiting the difference between dry bulb and wet bulb temperatures – lowering the sensible heat.

I don’t know but if this guy was for real you’d think he’d answer the basic question first: How much power input is required to get a ton of cooling (200 BTU/ minute)?

He seems to dance all around the subject, only mentioning ‘high COPS’, but never under the precise circumstances such things occur.

The old saying, “If you can’t dazzle them with brilliance, baffle them with BS”.

Again good to know, and again thanks for the info, sven.

Reducing the amount of energy required to run an air conditioner compressor has been a “holy grail” of engineering for decades. If GE has finally succeeded at that, then that’s wonderful to learn! But the question is, will the tech be inexpensive enough to compete with existing mechanical compressors?

All too many innovations and inventions are demonstrated in the lab, without there being any hope that they can be produced inexpensively enough for wide applications. I hope this isn’t one of those.

The heat pump in my Soul EV is no noisier than running the A/C, pumps out heat within ten seconds, and consumes about 10% of the power that the resistive heater in my other EV did to provide the same heat. I’ve used it to great effect between 20-60 degrees F. I certainly haven’t found any downsides.

Given the option I would love to have another heat pump in my next car.

“Longer delay before first heat is delivered”

It is just matter of setup or programming. Heat pumps typically have resistance heat strips for backup. Resistance heater doesn’t take significant space and and provide heat quickly as much as you want. That is what residential HVAC thermostats were doing for many years if you set them in “comfort” mode – resistance strips to overcome initial temperature difference, and heat pump to maintain temperature, with extra help from heat strips if outside is too cold and heat pump can’t keep up on its own.

As any car has A/C anyway, it isn’t so much extra hardware to use it as heat pump too.

I’d love to see more measurements of Tesla Power consumption when parked and plugged in. I believe these numbers are still much higher than any other EV, and quite wasteful.

This video and article is really off on the basics! 1: Wh is wrong – the guy at best measures W “Wh” in this case is mistaken for “W” = Watts = “Joules per second”. Thus saying “watts per hour” is effectively saying “joules per second per hour” which does not make any sense. 2: mph not relevant here mph is inaccurate for measuring power levels as it depends on how efficient driving is assumed which again depends on many things such as speed, weight, weather etc. 3: Peak power vs average power consumption Peak power is probably what this guy measured and refer to how much power the different function may draw at maximum. Average power on the other hand is the relevant measure as most functions will probably reduce power after a while or the Model S would make headlines for sterilizing male drivers using the heated seats (95 Watts is a lot for heated seats!). Example: typically the peak power of an car AC is 3-6 kW however the average consumption depending on temperature usually is no more than 1kW as it doesn’t have to run full power all the time. The take home message that heated… Read more »

Isn’t this a repeat of the first comment ie his units are not ‘Wh’ but watts *per* hour (of driving)?

It’s all academic to me as, without knowing what the ambient temperature was at the time the ‘tests’ were done, IT’S ALL UTTERLY MEANINGLESS.

I can’t speak for the “S” since I’ve never test driven one in cold weather. Of course my definition of “COLD” is probably another person’s view of Antarctic weather. But when I had my roadster, I the loss in battery range was double what was shown here, and that is keeping in mind the car had the smallest cabin in existence. With the much larger cabin in the GEN 1 Volt which turns the engine on at 26 degrees, and the ELR which turns the engine on at 32 degrees (that’s hot around here) – battery loss is harder to quantify since the engine turning on ‘prematurly’ makes watching battery drain harder. But while it is still off, and you need heat for defrosting or whatever, the heater in my current cars is definitely draining the battery faster than pushing the car down the road, so it cuts my range more than half. OF course, another 1 kwh is consumed pre-heating the battery – since in the GEN 1 volts there is ONLY a 2000 watt heater to do the heating, whilst the cabin may use (sometimes) the heat from the engine. Easy to do in the volt – much… Read more »

EV range reduction in cold weather in due to more reasons than just cabin heating.

For one, batteries are simply less efficient and can output less energy at cold temps.

Then you also have further decreases from battery heating, increased air drag from denser air, increased rolling resistance from cold tire rubber and deflated tires, increased drivetrain friction from more-viscous lubricants, etc.

Thanks for spelling that out.

Yes, the operating temperature of batteries is very important. That’s why most PEVs (Plug-in EVs) have battery heaters, to keep the battery within proper operating temperature. As I recall, even the Leaf has a battery heater.

And as you point out, running the heater does take some energy from the battery.

Exactly!
Cold battery doesn’t hold as much energy to begin with and because a cold battery is less reactive the C rate charge could get near zero, so no regeneration recovery until the battery is at a better temperature.
This all ad up.
Although there is solution for using regeneration to store heat in the battery core and put it to a useful task of heating it with what is actually lost.

I disagree with your statements, but, anyway, so what? The battery in my vehicles is in a ‘conditioned space’. There is no temperature change at all as far as the battery is concerned.

My tires usually are overinflated so in cold weather they are just right.

TO show what you just said is an irrelevancy, all I have to do is drive with the heater or high, or else not turn on the heater at all. Which is what I thought I just had said.

It’s rather unlikely that you will never, ever park your car for an extended period in a non-heated space. If so… then you need to get out more! 😉

Cars can’t be designed for only what the driver usually does with them. BEVs have to be designed to handle extreme weather conditions, because sometimes cars will be exposed to them.

The notorious Broder article in the New York Times, which was an error-filled report of an inexperienced EV driver’s misadventure with a Tesla Model S one bitterly cold weekend, was right on this: If you stay in a hotel in bitterly cold weather, and thus leave your BEV out in near- or sub-zero weather all night, it will experience significant loss of range. Either loss of range due to the battery being very cold, or loss of range due to the battery using its own power to keep itself warm. Either way, TANSTAFFL — There Ain’t No Such Thing As A Free Lunch.

If a BEV has to be left out overnight in very cold weather, it should remain plugged in all night so it can keep the battery warm without draining the battery.

I don’t see how Broder did anything wrong – you’re not the one to be critical of him.

I’ve left my volt out in the middle of a parking lot anytime I’ve stayed at a motel – and none of the motels around here will allow customers to plug in, although I did stay at a 1 – star hotel in ohio where i slipped an extension cord out the window to charge the car at 8 amps, but I had asked if I could recharge my battery since it is dead and they said ok as long as there were no cords in the hallway, but that’s not the general case. That was during the summertime, but I’ve also left the VOLT unplugged during the winter time…

Its unreasonable to expect John Q. Public to be responsible to plug a car in when there are absolutely no facilities to do so, and motels and hotels have existed for decades without providing the service.

Heisenberghtbacktotherootsandnuts

Nice information (while I agree that the chosen units might be confusing… )

What shocked me was the baseline of nearly 250W… Where does that come from? I really wonder… CPU running at full load? Controller? Anyone help me to understand, please!

Microprocessors and computer chips such as the CPU and the BMS don’t take anywhere near 250 watts to run. An entire desktop computer tower, with cooling fans running, may well use 250 watts when running a heavy computing load (source below), but that certainly won’t be an average power usage for a car’s CPU. Laptops use far less, so it’s quite possible that a typical car’s CPU uses a lot less than a desktop CPU tower.

One significant power draw may be the air compressor for the air suspension system, for cars equipped for that.

Aside from that, I’d guess that if the car has a 247 watt baseline power draw, most of the additional draw would be from the auxiliary power system which runs the radio, dashboard lights, the 17″ monitor, running lights, ventilation fans, cooling fans, and possibly the water pump for the battery heating/cooling system.

source:
http://michaelbluejay.com/electricity/computers.html

Well, I wouldn’t have believed it if I hadn’t seen it with my own eyes, but my 2011 VOlt was the first vehicle in my lifetime that acted like my grandfather’s car.

Listening to the radio in the garage for a couple of hours made the ‘full sized’ 12 volt battery go dead. In my case I had to do exactly what my grandfather did in his car when this happened – jumpstart the battery.

It was explained to me the 27 microprocessor systems in the car (and what they controlled, presumably) used all the extra juice.

KmanAuto looks naked without his trademark Fedora.

I stopped watching as soon as he said “Watts per hour.”

This article is a power/energy unit FACEPALM.