Confused about Climate System and Power Usage

[Atari2600]

So I went on a 100+ mile trip this morning. When the climate system was on my power was 305 Wh/Mi or so. When I turned it off the cabin was warmer and it started fogging up. This tells me the system was cooling. This was at 65 MPH headlights were on and it was raining. I reset the trip counter and drove around tonight in the dark with the lights on and windows down starting with the climate system off and my average was around 230 Wh/Mi. Of course it wasn't raining.

I read the manual pages 90 to 93 (PDF version) on the climate system and it does not explain if the heat is always restive or if it uses the drive unit and or battery for heat.

Seems like a big hit.

 

[S4WRXTTCS]

What I thought was funny was I was sitting in my car at home in my garage listening to music (yeah, I'm weird), and I could see the range drop. I think it was a mile every 30 minutes or so.

Eventually I was like screw this, and turned off climate control. It did get warm afterwards, but not terribly so.

In your experiment did you try simply turning off AC, but keeping the fan on?

 

[TLej]

Might be multiple things at play - rain adds drag/rolling resistance and increases power use all by itself. Heat definitely adds power draw, depending on what your settings are (recirc or fresh air, AC on or off, etc.). Heating or cooling outside air uses more power vs. recirculated, but recirc can increase humidity in the car which causes its own problems.

My S uses about 30% more power in winter (-20C to -30C) compared to summer, so the number can be a bit shocking if you’re not used to the idea. Should be less in less-extreme climates though.

 

[Trevor B]

On a somewhat related note ... is there a 1:1 mapping between miles driven and range? If I started at 280 miles and drove 6 miles, will it show 274 miles remaining? I'm assuming not (as it will depend on how the car was driven, AC etc).

 

[Derek Kessler]

Heat is always resistive. Period.

The battery miles rating versus how much you've driven is like a gas car: it varies depending on a dozen different factors that impact the power draw: climate control, weather, speed, terrain, etc.

 

[lolder]

Rain is a big range reducer as are headwinds. 70% of all winds are headwinds because of the vector summing of the car speed. Crosswinds are sometimes worse than headwinds. In "Auotmatic HVAC", the car may automatically run the heat and AC to dehumidify in conditions like yours.

 

[Atari2600]

In your experiment did you try simply turning off AC, but keeping the fan on?

The fan was set to 1. But I hit the one touch to turn off the climate system which is labeled item 6 in the pdf manual on page 91.

Rain is a big range reducer as are headwinds. 70% of all winds are headwinds because of the vector summing of the car speed. Crosswinds are sometimes worse than headwinds. In "Auotmatic HVAC", the car may automatically run the heat and AC to dehumidify in conditions like yours.

I did not notice any winds but you may be correct. I need to pick a 10 mile stretch of road and run it then go back an do it again with the exact same start and end point.

 

[jkirkwood001]

...Should be less in less-extreme climates though.

There's a place now with less-extreme climate...?
(sorry, couldn't resist black environmental humour)

 

[ℬête Noire]

When I turned it off the cabin was warmer and it started fogging up. This tells me the system was cooling.

I'm talking in generally here, not specifically about the Model 3 as I'm very fuzzy on it and haven't had a chance to do any testing (picking up the car Thursday), but humidity can lead to requiring heating AND cooling to dry out the air.

The only way there is condensation forming on the window is a temperature difference where the inside surface of the window is cooler than the interior air, which usually also means the outside is cooler. There's a weird intersection here, and I don't know how exactly the Model 3 HVAC behaves at that intersection so lots of a number of possibilities here.

P.S. The Model 3 lacks a manually selectable "fan-only" mode, so you don't really have much direct control on what happens at these edge cases outside of perhaps slamming the temp setting one way or another. Ability to manually select fan-only is something that people have requested and that I'd like to see if they can fit neatly into the UI.

 

[ewoodrick]

So I went on a 100+ mile trip this morning. When the climate system was on my power was 305 Wh/Mi or so. When I turned it off the cabin was warmer and it started fogging up. This tells me the system was cooling. This was at 65 MPH headlights were on and it was raining. I reset the trip counter and drove around tonight in the dark with the lights on and windows down starting with the climate system off and my average was around 230 Wh/Mi. Of course it wasn't raining.

I read the manual pages 90 to 93 (PDF version) on the climate system and it does not explain if the heat is always restive or if it uses the drive unit and or battery for heat.

Seems like a big hit.

I believe that your interpretation of the facts may be a little off.

I've had many trips with the AC on and consumption has been well under 250 Wh/Mi. That's in the heat of the summer with sun pounding down. So I don't think that the AC is the biggest culprit. I haven't tested the impact of the headlights, but the range definitely can be a big contributor. Seeing that increasing speed 5 mph can result in 10% more energy usage, having big pellets of water shot at you, along with the denser air, can definitely impact the energy usage.

Windows down have been proven to be very inefficient at highway speeds in ICE, let alone EVs.

You also have to be cognizant how the watt hour meter calculates the numbers. As displayed, it would seem to suggest that the number is an average over the period/mileage shown. It is not. It does seem to include the period/mileage, but that it definitely not its sole basis.
I've had the trip odometer at a few hundred miles and watched the watt hour meter go up and down as I'm changing speeds and climbing hills. At even 100 miles, there no way that changes over this small of distance can make significant changes in the average usage. So it seems to be some sort of weighted average.

 

[dhrivnak]

While the climate does use power I think you have other factors going on. Now at over 10,100 miles we are at 232 Watts/mile the vast majority is with climate control and mostly interstate. From my experience maybe 15watts/mile is from climate control.

 

[Atari2600]

P.S. The Model 3 lacks a manually selectable "fan-only" mode, so you don't really have much direct control on what happens at these edge cases outside of perhaps slamming the temp setting one way or another. Ability to manually select fan-only is something that people have requested and that I'd like to see if they can fit neatly into the UI.

I found this frustrating because I expected to be able to do more. I at least expected an economy setting which is basically the fan only setting that you brought up. So in manual you can control the AC but not the heat? Is the S and X like this? I still cannot believe the system cannot get any heat from the battery pack/drive unit as it warms up.

I have continually impressed people(including myself) with how fast the car can cool down from 100 to 75 in a parking lot in a matter of minutes. Maybe the white seats help. Overall still more impressed than unimpressed with the climate system.

I believe that your interpretation of the facts may be a little off.

I've had many trips with the AC on and consumption has been well under 250 Wh/Mi. That's in the heat of the summer with sun pounding down. So I don't think that the AC is the biggest culprit. I haven't tested the impact of the headlights, but the range definitely can be a big contributor. Seeing that increasing speed 5 mph can result in 10% more energy usage, having big pellets of water shot at you, along with the denser air, can definitely impact the energy usage.

Windows down have been proven to be very inefficient at highway speeds in ICE, let alone EVs..

I'm sure my interpretation is off I'm still trying to figure all this out. I drove today with it being 86 F and sunny and it used 235 wh/mi with the auto climate on at 75 F and 214 hr/mi with just my window down. Still more of a difference than I expected over the same traveled 15 mile run. So far I see better numbers with the window(s) down. I did not expect that. I'm driving 65 MPH.... Well probably closer to 74.

While the climate does use power I think you have other factors going on. Now at over 10,100 miles we are at 232 Watts/mile the vast majority is with climate control and mostly interstate. From my experience maybe 15watts/mile is from climate control.

Perhaps the heat was kicking on with the raining/humidity issue.