Cabin temp vs seat heaters with 3 passengers?

[bangtidy]

I understand that using the seat heater instead of the cabin heating is more efficient, but if the cabin is cold I find that my hands get a bit colder than I'd like and also, the windscreen and windows start to mist up so I really need to have some cabin heating.

So I'm finding that while driving on my own I tend to run the cabin at 20 degs C, fan speed 1, pointed up at the windscreen with AC off. With my seat heater at 2, this is comfortable keeps the screen and windows demisted and seems about as efficient as I can get without being uncomfortable.

My question is, with our first longer trip coming up this weekend with the wife and kids on board, am I best running a slightly warmer cabin temp (say 22/23) to keep them all happy rather than a slightly lower temp (say 20) but with all 4 seat heaters on?

My guess is that having all 4 seat heaters on will be less efficient than just running the cabin at 22 (low fan speed, no aircon) but I may be completely wrong on this.

Does anyone have any useful pointers or advice on this front?

Thanks!

 

[MrBadger]

You findings on low heat settings reflect mine, although I run temp at 18 or 19 and fan at 1 or 2 depending on humidity. Possible to run long stints with no heat which avoids drafts - windscreen demist causes one over hands. I do find my feet a bit under done though at times - I did read something that hinted that screen and feet did not heat at the same time - odd that controls do not reflect this but it would explain cooler feet.

Aircon appears not to use much energy, at least compared to cabin heat. Seat heaters good, but if I do use it, its only a few minutes on low. swmbo likes it though - she seems to get away with seat heat only for many journeys and this is reflected in her high efficiency ratings, even on relatively short journeys.

I often find that 19 gets too warm. I'm not convinced that temperature reading is particularly accurate and car heaters are notorious for that so it is no surprise. Comfort wise, 19 on model 3 equates to around 21 on our previous car. Even 3 up.

Remember that rear has separate airflow control - bottom left of hvac screen which I believe is influenced by driver side settings

 

[Jason71]

I understand that using the seat heater instead of the cabin heating is more efficient, but if the cabin is cold I find that my hands get a bit colder than I'd like and also, the windscreen and windows start to mist up so I really need to have some cabin heating.

So I'm finding that while driving on my own I tend to run the cabin at 20 degs C, fan speed 1, pointed up at the windscreen with AC off. With my seat heater at 2, this is comfortable keeps the screen and windows demisted and seems about as efficient as I can get without being uncomfortable.

My question is, with our first longer trip coming up this weekend with the wife and kids on board, am I best running a slightly warmer cabin temp (say 22/23) to keep them all happy rather than a slightly lower temp (say 20) but with all 4 seat heaters on?

My guess is that having all 4 seat heaters on will be less efficient than just running the cabin at 22 (low fan speed, no aircon) but I may be completely wrong on this.

Does anyone have any useful pointers or advice on this front?

Thanks!

I don't know for certain but my belief is that you are wrong.
I am not sure that anyone actually knows the power of the M3 seat heaters but typically they are only about 50watts max. There are also very efficient because the heat goes straight into you so little is wasted. So I would guess that adding 3 seat heaters would add only take about 150w/h even if it is double that at 300w/h that is about 1 mile per hour of range loss. The cabin heater on the other hand is heating the air and most of the heat will go straight out of the roof and windows. anecdotally it can consume 2000w/h.
So I appreciate that you cannot switch off the heater altogether and seat heaters don't warm you arms and legs but I still think you will find max seat heaters + minimum cabin heat the most efficient irrespective of no of passengers.
I doubt you will get away with AC off 4 up though. too much breathing going on. you will need it to dry the air and stop screen from misting

 

[bangtidy]

Thanks - that's very useful info - just what I was after.

 

[Adopado]

Just to comment on the aircon ... I have found it beneficial to leave it on. It seems to make little difference to consumption and it solves any tendency for misting, which is going to be greater with more people in the car. It doesn't impress anybody to be transported in a cold misted car! Once the car is fully up to temperature the consumption seems to back off, so long journeys are not an issue (that's different to the higher proportionate effect on short journey's). Don't get too paranoid about it. Set it and forget it. By far and away the biggest impact on range is how you use your right foot!

 

[bangtidy]

Just to comment on the aircon ... I have found it beneficial to leave it on. It seems to make little difference to consumption and it solves any tendency for misting, which is going to be greater with more people in the car. It doesn't impress anybody to be transported in a cold misted car! Once the car is fully up to temperature the consumption seems to back off, so long journeys are not an issue (that's different to the higher proportionate effect on short journey's). Don't get too paranoid about it. Set it and forget it. By far and away the biggest impact on range is how you use your right foot!

Yep, good advice. I'll shelve my plans to install a wood burning stove in the car

 

[DanThor]

I don't think too much about this. At the end of the day, it's a car. If you're cold, put the heating on untill you're not .

The car isn't much use if it can't keen you warm.

 

[bangtidy]

I don't think too much about this. At the end of the day, it's a car. If you're cold, put the heating on untill you're not .

The car isn't much use if it can't keen you warm.

Oh yep, I agree completely - I was just wanting to figure out the most efficient option.

 

[ewoodrick]

Are there any segments between charge locations that you feel that range is marginal?
If not, why worry?
Make family happy

 

[bangtidy]

It's a 180 mile round trip (Cheshire to York and back) which I'm hoping is do-able on a single 'tank'. I'm planning on stopping at the Leeds Supercharger on the way back anyhow just because I've not used one yet, but it would be nice to feel like it's not an absolute necessity for the trip. ABRP seems to think it's do-able and I'm pretty confident it'll be fine if I take it easy on the motorway.

As I'm still on the normal mains charger, there's a chance that I may not be able to set out with 100% as I'm usually down to about 60% when I get back home after work but I should have about 17 hours to charge up before we set off.

 

[Mr H]

I'd Just go to the Instavolt at YO26 6RL, Bannatynes for 20mins. Leeds SuC only has 2 stalls which I believe is usually busy. Instavolt is tap and pay with any contactless card

 

[ewoodrick]

Yep, take a stop, get out to stretch your legs a little.
If you have charging at your destination, then put the destination in the Nav and let the car let you know if you are going to make it.
If you don' have charging, then watch the energy graphs and see what the real estimated range is and make you decisions on when to stop.

Live a little, be adventurous.

You can't get over the range anxiety until you push your limits. But I think that I can say that a 200 mile trip in cooler weather is going to be pushing it. If you are going 60-65, it will probably work, but more than that you'll start getting the "Slow down to XX to make it to your destination" message. Yes, as long as the car is routing to your destination, it will tell you where to stop and how fast you can go.

 

[bangtidy]

Thanks all - very useful info. I did already have the Instavolt chargers at Bannatynes in mind as well as they seem like the quickest/easiest option around York.

Thanks again, great forum this!

 

[Jason71]

It's a 180 mile round trip (Cheshire to York and back) which I'm hoping is do-able on a single 'tank'. I'm planning on stopping at the Leeds Supercharger on the way back anyhow just because I've not used one yet, but it would be nice to feel like it's not an absolute necessity for the trip. ABRP seems to think it's do-able and I'm pretty confident it'll be fine if I take it easy on the motorway.

As I'm still on the normal mains charger, there's a chance that I may not be able to set out with 100% as I'm usually down to about 60% when I get back home after work but I should have about 17 hours to charge up before we set off.

You clearly have an LR or P in which case yes that should be doable. The biggest factor will be how fast you drive. if you plan to cruise at 70 you should comfortably be OK without charging (At 90 maybe not so much). Car Wow test this week on UK Motoways went 270 in an LR.

 

[bangtidy]

Yep, M3P. Suspect I'll be fine, but at least I'll have some contingencies plans now.

 

[Yev000]

Irrespective of aircon, heated seats, fan speed ... As others have said by far and away the most energy is used by the motor.

That said you take a large hit getting up to temperature (the heater and the cabin). Not sure if you would be able to turn the heater off completely, while keeping aircon on to demist.... Maybe set to temperature to 18-19, but that would still use a little heat.

Now the seat warmers sound efficient, but they are not really .... You can't use them to heat the cabin instead of preheat mode, the cabin will probably cool faster through the glass than the seats can heat it up.

With people inside the car, a lot of heat will be body heat. A lot of humidity as well....

Also keep in mind that all "heaters" are inherently 100% efficient at converting electricity to heat. The "inefficiency" comes from how much of that heat is used by you and how much escapes without being used.

So if you like breathing warm, dry air and being able see without wiping the windshield every 30 seconds, just set it 20 and auto and forget about it.