Let’s Look At Energy Consumption Of Tesla Model 3 Heater

OCT 16 2018 BY MARK KANE 35

Tesla Model 3 takes several kW for heating…if needed.

Tech Forum checked out how much energy a Tesla Model 3 would need to heat the cabin at 52°F (11.1 °C) with general heating maxed, while the driver’s seat heater is set for a single bar.

The car was connected to the grid, but charging was scheduled for a later time, which enabled us to see how much out of the available 32 amps the Tesla took for heating purposes.

As it turns out, it took around 4,800 W – around 20 A at 240 V (although at the beginning of the video it was even higher by 1-2 kW, up to 27 A).

When the general heating was off, the driver’s seat heater (set at one bar) used roughly 500 W (2 A at 240 V). That would mean general heating needed over 4,300 W.

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35 Comments on "Let’s Look At Energy Consumption Of Tesla Model 3 Heater"

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Some context would be nice.

No way the seat heater took 500 W. The 500 W must have been for everything drawing power in the car, including all of the computers.

No kidding. Not unless you like roasted rump for lunch. Most seat heaters are 10-50W. You really should have someone technical review these articles before posting them.

It was setting 1, so whatever that is. Probably around 12w.

Sounds like all the values listed are an order of magnitude higher than they should be.

I agree. If it needs over 2kw with a resistance heater something is very wrong. With a heat pump it would be under 600watts.
My coming EV part of my composite strength and safety systems cut the need for both heating and cooling. The composite body core is foam or honeycomb and inside of that is foam around the cabin for body impact crash protection plus more insulation.
Also only my windshield is glass. The other windows are Polycarbonate that transfer heat much slower.
Using a repackaged 6k btu window A/C with air doors to switch it from A/C to heat pump would be under 500wt and not run much as overkill.
Another is running the 90 Vette’s I got my suspension from A/C I kept from a variable speed DC motor one could get it down to 150 wts.

Contrast the Leaf heat pump pulls 400 watts.

Leaf also uses resistance heaters that draw significantly more than 400 watts when it needs to heat up the car. With my Leaf plugged into a 110V outlet, it can draw a max of 1,200 watts from the outlet. The preheat drew power from the battery even while plugged in, so it had to be drawing more that 1,200 watts.

You can also check the energy display which shows power draw by the climate control system. It can easily exceed 3,000 watts.

Good to know. Isn’t the heat pump mainly for the battery? Also at lower than say 25*F heat pumps don’t work so well.

Heat pumps drop in CoP with lower temperatures but modern heat pumps work well even at much lower temperatures than that.

A decade ago it was different.

2012 Leaf will draw easily 5kW when it really needs to crank up the heat. Fortunately it might only do that for 10min then drops back to about 1kW continuous. Obviously depends on start and target temperatures.
With a big battery maybe it won’t be that much of a problem using so much power, but it is interesting if they haven’t put a heat pump in to minimise heater impact on power usage.

The Leaf uses way more in the first few minutes. The energy monitor tells you.

This was basically a max heater test, AFAICS. Outside temperature only makes a difference at steady state.

Heat pumps are great from around 20-50 F, up to about 4x as efficient as a resistance heater. Tesla has a big battery and heat pump adds some cost and might shorten AC life (compressor is running more). Heat pump might also force some design decisions that possibly hurt AC performance. Need an HVAC expert to chime in here.

Mainly cost though, adding an auxiliary heater makes the car cost more. There is a reason Hyun-Ki’s PHEVs have no heaters and use the engine instead. Given battery size in Tesla it isn’t an issue. At 5 kW of heat at 75 mph heat won’t be that large percentage, and at low speeds where 5 kW is a large percentage the range is way longer than you drive in a day.

Leaf is critical to have a heat pump, when the heater might mean you don’t make your destination.

Hard to tell how this translates to range impact, especially on a long trip in the winter.
Might need lots of heating for the first few minutes but can that be dialed way back after?

Would be good to do a test like this:
– drive a frequently used route, preferably 100+ miles, on a day where no heat or A/C is needed
– drive the same route at various cold temps (5C, -5C, -15C, -25C average)
– start with full charge, record the remaining range at the destination
– write an article on InsideEVs to report – would provide a nice resource for other Model 3 owners who don’t travel as much
Might not be too late for some Model 3 owners in northern climates 🙂

Good points. Also all comparison tests should be done with exactly the same solar, wind, and weather, conditions, or as near as can be achieved..

Can’t speak for the TM3 yet, but in a 2012 Leaf the heater will draw about 5kW to get the cabin temperature up, then drop to around 1kW to maintain that temperature (from about 0C to 24C in my case).
If TM3 is anything like that, then you would be looking at about <6kWh for that first hour and then about 1kWh every hour after that. With a 75kWh battery, that's going to drop you to around 65kWh if you're drive 3-4hrs. Probably not a problem in most situations.

Forced Volt->Bolt Conversion

This leaves me wondering if Tesla (not being used to having arbitrarily large amounts of waste heat available like legacy car manufacturers) pays attention to thermal insulation for their vehicle cabins? While it’s true that air needs to move through vehicles at a fairly rapid rate in CFM compared to cabin volume, it’s also true that cold surfaces make us feel cold, so keeping exterior-facing surfaces in the car decoupled from the cold outdoors could help reduce heating consumption.

Rapping the roof of my Bolt suggests there’s no insulation up there, and that’s over a square meter of sky-facing metal radiating like mad on a clear day….

With what did you wrap your roof? The black CFRP roof of our i3 absorbs solar radiation and re-radiates it into the interior. I would like to wrap the roof with a durable IR-reflecting film of some sort. Is that what you used?

I believe Forced wrote “rapping” as in rapping his knuckles (knocking) on the roof. The sound suggested there was no insulation.

Good thing @bro1999 isn’t here.
Don’t say anything even remotely negative about the Bolt…

Tesla’s large glass roofs are probably worse for insulation than regular roofs, especially during winter nights (or dark days) lacking compensating sunlight.

On the other hand, equal headroom without glass would need a higher roof that has more drag and probably looks worse.

I have found the panoramic roof on my model S is excellent at both keeping the interior cool in the summer and holding heat in the winter. It’s clearly not ordinary glass. I was afraid of this before I bought my car but was pleasantly surprised at how well it works in practice.

I’d also question the 500 watt per seat heater… I actually measured the very good seat heaters in my LARGE KIA Amante (now discontinued), at 51 watts per seat. If it was 500 watts per seat – that plus the rear window heater would have used up everything the Alternator in the car could put out.

4300 watts doesn’t seem like very much on the other side of the scale…… Both my Bolt ev and Caddy ELR can each easily use around 6 kw or even more for the first minute or so.

I did this with my LEAF and I was able to actually use some battery while hooked up to 20A. I think I managed to peak at 6kW based on battery loss rate. [I used LEAFSpy to keep track of everything.] Pretty hardcore.

The best heat pumps I’ve seen (Mitsubishi with Hyper Heat) maintain 76% of their capacity at -13F, so making heat pumps that work in sub-zero temperatures is possible.

My owen can pull up to 2.3 kW from a 240 V outlet. Enough to fry two fat christmas ducks simultanousely.

Feeding 4.3 kW of heat into the cabin + 500 W from the seat – I would’t like to stay their!

Could it include some preheating of the battery or something?

Heating ~4 kW? just like in my I-MiEV!

Heating can go up to 6kW for my Fiat 500e. So 4300 seems very legit.

W or Wh?


For comparison: I have measured the heating loads in my Focus EV. At “full blast”, that is the temp setpoint set to maximum, the cabin heating can draw 7kW.

Heated seats draw less than 100W each.

This was all measured looking at the DCHV current as measured by the car over CANbus. I accounted for the base loads of the other accessories in these measurements.

Are Tesla using resistive heating rather than heat exchangers?

…And this reduces the range of the battery by X miles……

How many miles does heater use reduce the range by ?

If you use 10% of battery for heating, then you’d expect range to drop by about 10% as well. 7kWh of heating from 70kWh battery, 310mi range would drop to about 270mi range.
Likewise if you use 20% battery for heating then it would drop 20% range, so 14kWh heating would drop the 310mi range to about 240mi.
So running the heater in the TM3 LR would give you roughly the same range as the Bolt. I’d say that’s pretty good. Where I am out gets to about 0C and I’ve got only the 2012 Leaf for my testing. I’d hope the 2018 TM3 would be at least as good as my 2012 Leaf, if not significantly better. Just like we complain about Leaf not having active TMS, which is pretty much proven now, I’d say an EV without a heat pump is along the same lines.
Of course, I don’t have the TM3 to confirm this with, so hopefully someone can do some real world tests and tell us what it really does.