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Cold range numbers w/ various heat settings

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
Hi folks,

A quick few notes. I normally get around 135 Wh/km on highways in weather where I need no AC, heat, or open windows. Maybe windows are cracked a tiny bit, or low speed fan-only. LR AWD is rated for 150 Wh/km from what I can gather.

Temperatures in degrees C. Range in km. Because Canada. Numbers are for highway travel (net zero elevation change, i.e. there and back again).
  • 20C, no HVAC: 135 Wh/km (baseline)
  • 30C, Auto 22C: 150 Wh/km
  • 8C, Auto 22C, 0/3 Seat Heat: 172 Wh/km
  • 0C, Auto 20C, 3/3 Seat Heat: 180 Wh/km
  • 1C, Auto 22C, 0/3 Seat Heat: 180 Wh/km
  • 1C, HI 6/10 Fan, 1/3 Seat Heat: 198 Wh/km
I mostly found it interesting that cranking to HI temp (with fan speed at 6) "only" brought it to 198 (10% worse than 22C). This, of course, is about 30% more consumption than rated though. HI seems to still modulate the heater, it's not full power at all times but is definitely cranking out more heat than the highest numerical temp setting does.

I prefer setting it to HI because my hands get cold very easily. I can now sort of see what my preferences will cost me in terms of efficiency and dollars now. 20C is too cold for my hands, 22C is workable as long as I wasn't cold prior to hopping in the car.

My battery is almost always cold now, so regen is always a little limited until almost 40 minutes into driving. This hasn't been noticeable in driving behaviour in any way though, so it's not a big deal/ However, we'll see what happens once it gets colder :)

Hopefully this gives some perspective to new owners for this winter!
 

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
Very interesting. My heat on numbers are much worse.

My morning commute has a bit of a decrease in elevation so I usually do it in about 130Wh/km with AC.
4C, Auto 20C 3/3 Seat -> 225Wh/km

This is a 33km 45 minute commute.

I notice when I have auto heat on, it uses the AC for defog, blows all 3 (defog, face, feet) at 4 or higher.

Interesting datapoint! The length of my drives may have something to do with it. Generally about 60km, but the commute time is almost the same (50 minutes) I also see the all 3 directions + AC for the first few minutes, but it generally changes after a few minutes (then it's floor & hands/face). Especially if the AC is actually running for defogging purposes, there would be some extra usage from that.
 

justsomeguy

Member
Jul 4, 2019
295
288
Vancouver, Bc
Interesting datapoint! The length of my drives may have something to do with it. Generally about 60km, but the commute time is almost the same (50 minutes) I also see the all 3 directions + AC for the first few minutes, but it generally changes after a few minutes (then it's floor & hands/face). Especially if the AC is actually running for defogging purposes, there would be some extra usage from that.
I tried to edit my post and accidentally deleted it. Oops...

Longer drive + approx same time would probably explain away a bunch of the discrepancy. I used to worry about losing the range, but the commute home is in much warmer and sunnier weather so I don't get a range hit on that.
 

ewoodrick

Well-Known Member
Apr 13, 2018
5,285
3,735
Buford, GA
Air Conditioning and Heat are not proportional items. i.e. setting the temperature at 10 and setting at 20 doesn't mean different levels of A/C and heat.
A/C and heat are on/off items. Just as your A/C at home, the compressor will come on and off as needed, the fans can follow the cycle or stay on all the time.
So it is very possible that when you change the temps, you don't see an immediate change in the energy use, it may be minutes later, or even never (if it wasn't really needed that much).

But indeed, your number follow the 30% degradation that is often used.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,428
12,678
San Diego
Hi folks,

A quick few notes. I normally get around 135 Wh/km on highways in weather where I need no AC, heat, or open windows. Maybe windows are cracked a tiny bit, or low speed fan-only. LR AWD is rated for 150 Wh/km from what I can gather.

Temperatures in degrees C. Range in km. Because Canada. Numbers are for highway travel (net zero elevation change, i.e. there and back again).
  • 20C, no HVAC: 135 Wh/km (baseline)
  • 30C, Auto 22C: 150 Wh/km
  • 8C, Auto 22C, 0/3 Seat Heat: 172 Wh/km
  • 0C, Auto 20C, 3/3 Seat Heat: 180 Wh/km
  • 1C, Auto 22C, 0/3 Seat Heat: 180 Wh/km
  • 1C, HI 6/10 Fan, 1/3 Seat Heat: 198 Wh/km
I mostly found it interesting that cranking to HI temp (with fan speed at 6) "only" brought it to 198 (10% worse than 22C). This, of course, is about 30% more consumption than rated though. HI seems to still modulate the heater, it's not full power at all times but is definitely cranking out more heat than the highest numerical temp setting does.

I prefer setting it to HI because my hands get cold very easily. I can now sort of see what my preferences will cost me in terms of efficiency and dollars now. 20C is too cold for my hands, 22C is workable as long as I wasn't cold prior to hopping in the car.

My battery is almost always cold now, so regen is always a little limited until almost 40 minutes into driving. This hasn't been noticeable in driving behaviour in any way though, so it's not a big deal/ However, we'll see what happens once it gets colder :)

Hopefully this gives some perspective to new owners for this winter!

Note that all of these increases are scaled down the faster you go. You said highway speeds - but there would be a big difference between 55mph and 80mph. (Obviously aero losses would be a lot higher at 80mph, but that is mostly independent of temperature so only a tangentially related topic - aero is of course a bit worse in cold dense air.) And the increase would be a lot larger for someone who averages 20mph on their winter commute.

Wh/mi adder = (Accessory watts) / (velocity (mph))
 
Last edited:

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
Note that all of these increases are scaled down the faster you go. You said highway speeds - but there would be a big difference between 55mph and 80mph. And the increase would be a lot larger for someone who averages 20mph on their winter commute.

Wh/mi adder = (Accessory watts) / (velocity (mph))

Absolutely! I've often wondered what this looks like on a graph, especially if there's some "break-even" point between wind resistance vs. energy used for HVAC over time. And my highway travel is generally between 90-105 km/h (56-65 mph) without much in terms of traffic slowdowns, so that's a good point. However, I expect that speed will go down as winter driving conditions come into play, so this is probably only the beginning of extra power draw.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,428
12,678
San Diego
especially if there's some "break-even" point between wind resistance vs. energy used for HVAC over time.

Good point. Certainly seems that in extreme winter conditions, the maxim to “just slow down” to reach your destination with charge remaining may not apply - unless of course you also turn off the heat (which presumably you normally would, if arrival was in doubt).

In general there is always a break even due to static losses - this is the main reason why the optimal speed for maximum range is 20-30 mph and not 0-5mph. Extra static losses increase that optimal velocity for maximum range. (There are also drivetrain efficiency differences vs. load and RPM which make a difference for this number, but that’s not worth getting into...and when heat is involved I am pretty sure those drivetrain differences have little overall impact on the optimal speed.)
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,428
12,678
San Diego
I tried to edit my post and accidentally deleted it. Oops...

Longer drive + approx same time would probably explain away a bunch of the discrepancy. I used to worry about losing the range, but the commute home is in much warmer and sunnier weather so I don't get a range hit on that.

Related to the prior posts, you only averaged 44km/h, so that is probably the main reason your adder is nearly twice as large.

Definitely the length of the drive matters too if your car is not pre-conditioned, since initial static loads (by static I mean watts are independent of speed) will be very high, and then taper off to the steady-state heating requirement for thermal equilibrium.
 
Last edited:

justsomeguy

Member
Jul 4, 2019
295
288
Vancouver, Bc
Related to the prior posts, you only averaged 44km/h, so that is probably the main reason your adder is nearly twice as large.

Definitely the length of the drive matters too if your car is not pre-conditioned, since initial static loads (by static I mean watts are independent of speed) will be very high, and then taper off to the steady-state heating requirement for thermal equilibrium.
Definitely, the math works out so that almost the entire increased usage is explained by his almost 2x distance in essentially the same amount of time.

My commute in is also (in this season) in almost pitch black so there's no sun adding any additional heat to the car.

I schedule my charge to start 1.5 hours before I leave in the morning so the battery is relatively warm, and i preheat the cabin 10-15 minutes before unplugging. The charging thing alone gives me 60-70%ish of max regen available vs almost nothing in freezing temps.
 
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