Heating system Model S

[darthy001]

I'll have to crank the heat some time and watch the power meter and estimate the draw. It's quite significant from what I remember.

Such a test would be extremely appreciated. I believe many of my fellow Norwegians would feel the same.

Anything a bit below freezing would do. After having seen your roadster in the snow I believe you sometimes get conitions similar to winter here in Norway

 

[ToddRLockwood]

How did that affect window fogging? I've always found that unless I keep heated air flowing and avoid the re-circ function, I'll get terrible fogging on all windows. Sometimes, even in cool, damp conditions I have to keep the a/c compressor running to avoid window fogging.

Good question. Does the heat pump give one the same anti-fogging benefit as running A/C in an ICE car? I often run the A/C in my Beetle along with the heat to get rid of excess moisture in the spring and fall.

 

[eledille]

Such a test would be extremely appreciated. I believe many of my fellow Norwegians would feel the same.

Yes, I certainly feel that way!

I think the heat pump may use more power when just started as it pressurizes the system, but I'm not sure. I'm very interested in updates on how the heater performs when it's really cold and how it affects range.

 

[Doug_G]

How did that affect window fogging? I've always found that unless I keep heated air flowing and avoid the re-circ function, I'll get terrible fogging on all windows. Sometimes, even in cool, damp conditions I have to keep the a/c compressor running to avoid window fogging.

What I've found with the Roadster is that as long as you're driving, there's enough air flow leaking through the system to keep the windshield clear. If you come across a small town and get stopped at a traffic light then it fogs up. So what I do is I leave the heat on but the fan off, so the heat is actually off. When I get to a small town I flip it over to windshield and turn the fan on the lowest setting. That keeps it clear until I get moving again.

None of the above is likely applicable to Model S.

 

[RDoc]

Good question. Does the heat pump give one the same anti-fogging benefit as running A/C in an ICE car? I often run the A/C in my Beetle along with the heat to get rid of excess moisture in the spring and fall.

That sounds to me like a very good question indeed. AC on with windshield heat for de-fogging works because the AC coil is cold and condenses out the interior air's moisture. The heater then lowers the relative humidity by heating the air so mist on the windshield inside evaporates. Interior heat is free in an ICE vehicle, so that's not a problem.

A heat pump produces heat on the interior of the car and cold outside, or in the cooling system, so there's no dehumidifying function beyond the temperature difference the heater produces. I wonder if the Tesla has a windshield heating system that uses the AC to chill the air, then resistance heaters to warm it up or possibly an interior to interior circuit in the heat pump.

Anyone with an S have any experience with the de-fogging function of the heating system or know how it works?

 

[Jason S]

I've had my Model S for three weeks and temperatures in Michigan ranged from 30 Degrees Fahrenheit (Freezing) to 60 Degrees Fahrenheit. From my experience:

1) When temperatures were at or just below freezing, using the HVAC (without seat warmers), the Model S warmed up to 70 Degrees Fahrenheit (cabin temperature) in approximately 2 minutes (or less).
2) Keeping the cabin at 70 Degrees did not significantly reduce range. I drove 70 MPH on the highway with the outside temp at 34 Degrees Fahrenheit and the cabin temperature at 70 Degrees Fahrenheit. I drove 120 miles (all highway). My Watts Per Mile was 315 (270 Miles of range).
3) While warming the cabin has a minimal reduction on range, I noticed that warming the battery does require a lot of juice. In other words, at temperatures of 32 degrees Fahrenheit or below, the first few miles of driving at city speeds (30 MPH to 40 MPH) translated into something like 480 to 520 Watts Per Mile. However, after 2 to 4 miles of driving, the battery did warm up to its optimal temperature and my WPM dropped to something like the low 300s.

I hope this helps.

Thanks, this info is very helpful and definitely answers my question. I appreciate the help!

For reference, this afternoon/evening (some with lights on) I was driving 70 for about 150miles at saw about 300Wh/mile but didn't need to use heating or cooling at all. Did use the lights for about an hour. For the entire 200 mile trip the average was 304Wh/mile with mostly freeway driving.

Therefore I'd say the heating and lights are maybe a 5% difference (15/300).

 

[cinergi]

I've used the defroster a few times to defog. I didn't pay attention to what it was doing (AC + Heat? Would be hard to tell) but it was effective.

 

[eledille]

I really wish Tesla would add a tab to the display which would show stats like instantaneous voltage, amps, temperatures (battery inlet, battery outlet, motor, inverter, ...) etc. That would make so many questions so much easier to answer, and they have those numbers in there somewhere already.

With this info, we would know exactly how much power the heater consumes, why the car just went into reduced power mode, and any number of other interesting questions.

 

[William13]

When I start the car in the cold it draws a lot of power for a few minutes, warms up quickly, then the power usage goes down. It stays higher than usual for another few miles then drops to something similar to it warmer weather standard.

Maybe someone with more patience than I have will try to answer this question.

 

[cinergi]

Heat & A/C fully-cranked (was in my garage so not bitter-cold but should consume approximately the same power as I manually set everything to max):

- - - Updated - - -

I've used the defroster a few times to defog. I didn't pay attention to what it was doing (AC + Heat? Would be hard to tell) but it was effective.

This does run the AC. Separate systems.

- - - Updated - - -

Counting pixels (haha) it's about 16 out of 43 to 20 kW or about 7.5 kW for full blast.

 

[Doug_G]

Counting pixels (haha) it's about 16 out of 43 to 20 kW or about 7.5 kW for full blast.

Interesting - about the same as the Roadster at max heating.

 

[tezco]

My Leaf heats a water bath instead of the air directly. This means that the blower circulates cold air for about 10 minutes until the water heats up. So, I normally call the car up on the App and turn on the heat about 10 minutes before I plan to leave. The Leaf uses up to about 4,000 watts for heating initially when in regular drive mode. Once the cabin warms up the power needed drops unless it is really cold outside. If you switch to Economy mode (gives you better regen), the heater input is cut back to 1,500 watts, which isn't sufficient below about 20 degrees. Tesla system works better.

 

[cinergi]

So I just drove around for 100 miles for the fun of it this evening ... it was about 60F in my garage, 35F in Boston, and 26F during the coldest parts of my trip (usually 30F or under). I was attempting to observe whether the 19" winters had better range properties than the 21" summers. I can't tell -- too hilly around here. But since I was doing that, I had the heat off. The insulation in the car is pretty impressive.
First, I actually had to go full manual and set the temp to LO (no heat), fan on 1, and blow air on windshield -- because otherwise I'd fog up!
So I've got air blowing into the cabin ... yet after 45 miles of driving, the cabin was 57F. I had the heated seat on, wearing a t-shirt and the tesla sweater (I don't think it was zipped up, either). I was pretty comfy the first 25 miles ... and then I could tell I should have the heat on -- but it wasn't bad. After 45 minutes (where it was 26F out and cabin was 56-57) I turned the heat to 70. It got into the mid-to-upper 60's in the cabin pretty quick. WHPM took a pretty good hit for the first several miles. After that, I was doing between 375 and maybe 410 WHPM while driving 72 MPH with the heat at 70 (that's with hilly terrain -- very difficult to observe impact of turning the heat on). Once the cabin got up to temp, the fan was running at 2-3 ... couldn't hear a thing... very comfortable inside.

Yesterday my car was sitting outside in 35F temps for several hours, but the inside of the car never got that cold (???) so heating it up and whatnot was quick. Will be really really interesting to see a cold-soaked car in 0F weather!

 

[strider]

Does it automatically turn on the A/C when put into defrost mode?

 

[cinergi]

Does it automatically turn on the A/C when put into defrost mode?

If you hit the defrost button, yes. In this case, I just manually selected to direct air to the windshield.

 

[sreehyd]

So I just drove around for 100 miles for the fun of it this evening ... it was about 60F in my garage, 35F in Boston, and 26F during the coldest parts of my trip (usually 30F or under). I was attempting to observe whether the 19" winters had better range properties than the 21" summers. I can't tell -- too hilly around here. But since I was doing that, I had the heat off. The insulation in the car is pretty impressive.
First, I actually had to go full manual and set the temp to LO (no heat), fan on 1, and blow air on windshield -- because otherwise I'd fog up!
So I've got air blowing into the cabin ... yet after 45 miles of driving, the cabin was 57F. I had the heated seat on, wearing a t-shirt and the tesla sweater (I don't think it was zipped up, either). I was pretty comfy the first 25 miles ... and then I could tell I should have the heat on -- but it wasn't bad. After 45 minutes (where it was 26F out and cabin was 56-57) I turned the heat to 70. It got into the mid-to-upper 60's in the cabin pretty quick. WHPM took a pretty good hit for the first several miles. After that, I was doing between 375 and maybe 410 WHPM while driving 72 MPH with the heat at 70 (that's with hilly terrain -- very difficult to observe impact of turning the heat on). Once the cabin got up to temp, the fan was running at 2-3 ... couldn't hear a thing... very comfortable inside.

Yesterday my car was sitting outside in 35F temps for several hours, but the inside of the car never got that cold (???) so heating it up and whatnot was quick. Will be really really interesting to see a cold-soaked car in 0F weather!

Thanks Cinergi for all your tests and observations . It is impressive to note that MS is very well insulated and holds inside temperature. So just to get a fair understanding, How was energy consumption with & without Heat/AC on in same drive and speed etc ? If you have already tested .

 

[Kipernicus]

Counting pixels (haha) it's about 16 out of 43 to 20 kW or about 7.5 kW for full blast.

So I just drove around for 100 miles for the fun of it this evening ...

You are da man! Always going above and beyond the call of duty. Thanks

 

[cinergi]

Thanks! It's easy -- this stuff, including driving the car, is a lot of fun! So it's not "work" to me :smile:

With respect to HVAC on vs. off, it's very difficult for me to get an accurate number given the hilly terrain plus the fact that I've changed my tires recently. I will do five circular trips (30 miles each): two with heat on, two with it off, and the first one to "warm up" the car and remove any "first drive results in different numbers" stuff at some point.

 

[ddenboer]

One thing I've noticed in my car is that I almost always have to have air blowing on the windshield to keep from fogging (we've had a lot of rain here lately). When I do this, no matter what temp I have the car set to, it never reaches it, and I can actually feel the cold air blowing on me instead of the warm.
Also, no matter what temp I set to, or what ventilation option, I have never felt air blow into the back seats, and my kids complain about being a little cold in the morning rides to school.

 

[Jeeps17]

... snip ... no matter what temp I set to, or what ventilation option, I have never felt air blow into the back seats, and my kids complain about being a little cold in the morning rides to school.

That could be an issue, especially for those using rear facing seats, if the second row passengers are feeling chilled.

Is there ANY ventilation back in the trunk? The kids sitting there in winter will have the hatch window radiating cold right above them...