Heater on always vs frequent on/off, which is more efficient?

[StrykerFoxx]

Let's say I got a 1 hour commute to work in the winter. Which of the following would be more efficient? (by efficient I mean minimize power draw, as well as minimize wear and tear on all components)

1) Set comfortable temp (say 20 C or 68 F) when I get in the car (or a few mins prior via the app) and just keep it that way the whole drive.

2) Set it to maximum temp for a short while, then turn it off when the cabin gets hot, then turn it back on when I start to feel cold again, and repeat.

3) Something else.

I have a Model 3 with the heat pump.

 

[jjrandorin]

3) Something else - either

A) Set cabin to a temperature you can tolerate (if thats 68 degrees or whatever it is).
B) turn on Seat heaters to stay warm, and lower cabin temp if you can

Or

A) Realize that your commute is only 1 hour, and as long as your total commute round trip to work and back does not drain your entire battery, just set the cabin to be comfortable and drive, since any efficiency gains are basically like hypermiling for fun, but you are talking about commuting to work so you should be comfortable.

 

[DuncanM]

Let's say I got a 1 hour commute to work in the winter. Which of the following would be more efficient? (by efficient I mean minimize power draw, as well as minimize wear and tear on all components)

1) Set comfortable temp (say 20 C or 68 F) when I get in the car (or a few mins prior via the app) and just keep it that way the whole drive.

2) Set it to maximum temp for a short while, then turn it off when the cabin gets hot, then turn it back on when I start to feel cold again, and repeat.

3) Something else.

I have a Model 3 with the heat pump.

Assuming you charge at home: Set the car to preheat the cabin and battery prior to leaving for work. when on the road set the cabin temp to ~68-70f with air directed to the windscreen, seat heater on low. Fan to whatever speed keeps the windows from fogging.

 

[Sophias_dad]

If you really want, you can check it experimentally on the power usage screen in the car.

I doubt anyone has the answer yet. What a colossal PITA to save a tiny amount of power and be intermittently uncomfortable your entire trip!

I have a 2018 and I might open the HVAC screen once a year. I can't imagine opening it a dozen or more times per trip to turn off the HVAC. It might also be arguable that the accident you are likely to cause by looking away from the road to repeatedly screw with the HVAC is not worth the potential savings. (Ya, I know you could probably say "HVAC ON" and "HVAC OFF" or whatever).

 

[GtiMart]

you can also just hold the temperature on the lower bar for a second to turn hvac off, you'll see it gray out. Just press it once to turn it back on. I would believe the gain to be minimal if there is one... in fact, it might even be a loss. You'd really need to test it to know. I agree with others on the personal opinion though: minimal gains if any compared to adjusting your speed, if you need to save energy. Otherwise, just set to what's comfortable and drive.

 

[derotam]

Let's say I got a 1 hour commute to work in the winter. Which of the following would be more efficient? (by efficient I mean minimize power draw, as well as minimize wear and tear on all components)

1) Set comfortable temp (say 20 C or 68 F) when I get in the car (or a few mins prior via the app) and just keep it that way the whole drive.

2) Set it to maximum temp for a short while, then turn it off when the cabin gets hot, then turn it back on when I start to feel cold again, and repeat.

3) Something else.

I have a Model 3 with the heat pump.

There are so many variables that would have to be taken account of, there really is no cut and dry answer here. You mentioned "when I start to feel cold again"...that right there is a huge variable and is going to depend on outside temperature and speed of travel. You can attempt to get some measurements but the results won't be consistent due to temperature and humidity outside.

As far as leaving the system on, the most efficient would be to put it down to 65F(or whatever the lowest set point is that would stop heating) For my 2018 M3 LR RWD that set point is 65F, if I put it to 64 then I get no heat.

As far as turning it off and on you can see an efficiency gain but ONLY if your cold tolerance is high. Remember when you do this every time you turn that heat on it is going to be using max power to warm the cabin up. The bigger problem I think though is that if you just turn the system off, then you end up getting a cold spot at your feet pretty quickly because of the lack of air movement. You can fix that by putting the set point to LO and turn the A/C off to keep the air circulating...but that can be a hassle. Then there is always humidity issues...if your cabin starts fogging up then you HAVE to turn the system on to clear that and once you start having that issue you definitely might as well just keep a static set point.

There is no static answer for this. You can change your operation based on the current weather condition to gain efficiency but it is going to be your own experiments to figure that out.

Currently(for experimental curiosity) I am actually leaving the system off as much as possible to see what kind of efficiency I can get on my 35 mile commute to work. With current weather conditions(upper 40F's) I can save approximately 50Wh/mile which ends up being about 1.75kWh for the whole trip. From a cost perspective that is minuscule. From a percentage it is significant.

 

[zoomer0056]

Appeoach this the same way as you do with the temperature in your house.

 

[3sr+buyer]

Appeoach this the same way as you do with the temperature in your house.

It would help if the HVAC controls had two temperature settings, a lower "heat" setting and a higher "AC" setting, like many house thermostats have to allow a range of temperature that does not require either heat or AC (for example, you may want to set the heat to 63F/17C and the AC to 77F/25C if you are comfortable without heat or AC between those temperatures).

 

[davewill]

It would help if the HVAC controls had two temperature settings, a lower "heat" setting and a higher "AC" setting, like many house thermostats have to allow a range of temperature that does not require either heat or AC (for example, you may want to set the heat to 63F/17C and the AC to 77F/25C if you are comfortable without heat or AC between those temperatures).

Either that, or a "Heat On/Off" button similar to the "A/C On/Off". I hate getting into the car in the morning and having the heat kick on just because the inside temp is a couple degrees below my usual setting of 72. In the winter time, I pretty much have to lower the temp every morning, and then raise it once the day gets started. Separate heat and cool temps would be better, but a no heat button would work for me since in SoCal, I rarely need it.

I will note that it's a universal failing on all the cars I've ever owned with a set temperature.

 

[3sr+buyer]

Either that, or a "Heat On/Off" button similar to the "A/C On/Off". I hate getting into the car in the morning and having the heat kick on just because the inside temp is a couple degrees below my usual setting of 72. In the winter time, I pretty much have to lower the temp every morning, and then raise it once the day gets started. Separate heat and cool temps would be better, but a no heat button would work for me since in SoCal, I rarely need it.

I will note that it's a universal failing on all the cars I've ever owned with a set temperature.

There are cars where you can turn off heat and AC. So it is not like it is that hard of a thing for Tesla to include in a future software update.