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Cabin Heater in Blizzard

brucet999

Active Member
Mar 12, 2015
2,694
1,500
Huntington Beach, CA
On another forum, one of the posters, who lives in Maine, opined that a Model 3 could be "life threatening" because of limited range compared to an ICE vehicle. Further on, he asserted that, if trapped in a heavy snowstorm, an ICE driver could last days, idling the car to keep the cabin heating going, making sure to occasionally clear the tailpipe of snow, whereas a Model 3 would run out of battery after a few hours of cabin heating.

I think he is wrong if the ICE vehicle is a comparable medium sized luxury sedan.

Who has good data on the cabin heater load required to maintain a reasonable temperature with ambient temp of, say -20F? I've seen one post on Tesla Forum in which a guy heated a Model S from -21F to 70F, using 7.2 kWh to do it, but he had outside air selected and there was no measurement of energy consumed maintaining cabin temp.

I can find ICE fuel efficiency and fuel tank size data easily, but I wonder how long such a car can idle on a gallon of gasoline?
 

Tam

Well-Known Member
Nov 25, 2012
9,147
7,852
Visalia, CA
..."life threatening" because of limited range compared to an ICE vehicle.. Further on, he asserted that, if trapped in a heavy snowstorm, an ICE driver could last days, idling the car to keep the cabin heating going, making sure to occasionally clear the tailpipe of snow, whereas a Model 3 would run out of battery after a few hours of cabin heating...

Those might be real and valid concerns because Tesla Superchargers are not at nearly every intersection and highway exit.

However, there have never been any reports of deaths from EVs that ran out of energy in winter even in the arctic regions like Norway.

However, there've been quite a few reports of deaths from ICE that got lost.

Lessons learned from Kim tragedy

Also, there's no report of deaths from idling an EV while there are many reports of deaths from Carbon Monoxide poisoning from an idling ICE.

For storm/fire evacuations, there's no report of waiting in a long line full of EVs but there are many reports of long lines of ICE waiting for refuel.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,419
12,664
San Diego
Who has good data on the cabin heater load required to maintain a reasonable temperature with ambient temp of, say -20F? I've seen one post on Tesla Forum in which a guy heated a Model S from -21F to 70F, using 7.2 kWh to do it, but he had outside air selected and there was no measurement of energy consumed maintaining cabin temp.

It’s about 7kW for the cabin heater at 100% load so if you start at 50% SoC and say it runs at 50% load you could estimate it will last about 10 hours.

35kWh/3.5kW = 10 hours

This is just a quick back of the envelope calculation - there are other things that would likely consume some power at -20F - stator heaters are about 3kW each. But when those would be on is not well understood by me (no experience in SoCal).
 
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KenC

Active Member
Sep 4, 2018
3,707
3,363
Maine
Honest, it wasn't me. Can't remember the last real "blizzard" here in Maine, where vehicles got stranded for days. During Winter, every other vehicle on the road is a pickup with a snow blade on front, so roads get cleared pretty quickly. For something disastrous, you'd have to be way up north on a remote logging road. And if you're up there, you should know enough to be prepared.

There's a Tesla Bjorn video where he camps out in below zero temps in his Tesla, and does all the measurements. The problem with being in an ICE in a blizzard, is that people fall asleep with the engine on, and forget to get out and clear the snow away from the tailpipe.
 

ArcticStation

Supporting Member
Supporting Member
Oct 10, 2018
181
270
Maine
Wow! This is something I never worry about, and I spend a lot of time on Maine's rural roads.

In winter I (and most prudent Mainers) carry a simple emergency kit. For me its a heavy blanket and extra warm dry clothing, some MREs, a good flashlight, matches, small shovel, water and meds--items that will keep me going for a considerable time without having to run the heat. I won't be toasty warm or well fed, but I will survive.

IMHO my kit, coupled with prudent trip planning, leaving with a fully charged phone and informing a friend or family member of my itinerary provides me with the safeguards I feel I need to venture out during a Maine winter irrespective of how long the car heater will last.

Perhaps if one chooses to NOT prepare for the challenges presented by a typical Maine winter, then an ICE with a full tank of gas may be a more prudent option.
 

brucet999

Active Member
Mar 12, 2015
2,694
1,500
Huntington Beach, CA
It’s about 7kW for the cabin heater at 100% load so if you start at 50% SoC and say it runs at 50% load you could estimate it will last about 10 hours.

35kWh/3.5kW = 10 hours

This is just a quick back of the envelope calculation - there are other things that would likely consume some power at -20F - stator heaters are about 3kW each. But when those would be on is not well understood by me (no experience in SoCal).
Of course that assumes that you need the much to maintain interior temp. I have no data as to the rate of heat loss.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,419
12,664
San Diego
Of course that assumes that you need the much to maintain interior temp. I have no data as to the rate of heat loss.

Yeah, it is on that order. At 70mph that would imply an adder of 50Wh/mi which is quite a reasonable result and may even be low for -20F.

70mph*50Wh/mi = 3.5kW.

Obviously convective losses would increase at 70mph but the various errors likely cancel.

Easy enough to measure, anyway. Next time it is cold set the cabin temp to a fixed value and see how much energy it takes. Either by monitoring rated miles and converting to energy directly, or by monitoring the wall consumption (while backing out AC-DC losses).

I’ve done this before and it takes about 1.5kW to maintain 73 degrees with outside temperature of 50F. As I recall. Too lazy to look up my post!

All super easy to determine within 5-10% or so.

Strong argument for a heat pump in California, would drop that number to 500W. If it is -20F out the heat pump will not do so great as the thermodynamic efficiency is lower as I recall, let alone practical considerations of the evaporator freezing up and requiring some other source of resistive heat.
 
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SSedan

Active Member
Jul 24, 2017
2,948
2,328
Greenville Wisconsin
I am a rational person who enjoys my EV while still recognizing ICE are useful and will be the norm for decades. Both have their strengths and weaknesses.

The answers you get from both ends of the spectrum are delusion.
Yes the total energy in a gas tank can be more than the capacity of the battery, but an ICE wastes a lot of energy to make the waste used to heat the cabin.

Yes ICE make CO and CO2 but in reality it is extraordinarily rate for this to harm people stranded, potentially yes kind of like potential for EV batteries to catch fire.


Provided the battery or tank isn't empty when you become stranded either will keep you warm a good while. If you really think you could be stranded longer than an EV battery will hold out I suggest a satellite phone.
 
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Watts_Up

Active Member
Mar 4, 2019
3,643
2,456
In a galaxy far, far away
On another forum, one of the posters, who lives in Maine,
opined that a Model 3 could be "life threatening" because of limited range compared to an ICE vehicle.

Further on, he asserted that, if trapped in a heavy snowstorm, an ICE driver could last days,
idling the car to keep the cabin heating going, making sure to occasionally clear the tailpipe of snow,
whereas a Model 3 would run out of battery after a few hours of cabin heating.
Some good information from Bjørn Nyland;

 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,419
12,664
San Diego

So 1.5kW with fan speed one, 21C, with -19c or so outside. My guess is it was pretty chilly in the car. A little surprised it is that low, but keeping that fan speed low definitely restricts the output of the PTC. My numbers quoted (for 73/50 degrees, which were about the same 1.5kW) were basically full blast heat numbers, getting the cabin nice and toasty.

If you are trying to fend off death seems like you might be able to stretch the battery for a day or two.
 

Tam

Well-Known Member
Nov 25, 2012
9,147
7,852
Visalia, CA
...an ICE driver could last days...

An ICE sedan can use as much as 0.7 gallons while idling.

The gas tank for 2006 Saab 9-2X is 15.9 gallons.

15.9 gas tank / 0.7 consumption= 22.7 hours.

Model 3 75 kWh / 7kW = 10.7 hours.

So, in theory, the Saab would give a stranded owner more time but in reality, when people are lost, they would just run out of fuel, either in gasoline or battery, as James Kim did. They started the campfire with woods, paper magazines, and their own perfectly good tires.

If an owner was stranded with a Tesla, and if the authority were looking for the missing persons as in James Kim's case, I think Tesla could help by tracking down when and where was the last transmission of the car's telematics.

But as mentioned by @SSedan, a satellite phone would be a good investment for those who worry about being stranded either in ICE or EV.
 

BabyYeggie

Member
Jul 22, 2019
30
30
YEG
Here's a snippet from a trip I made on the coldest day of the year. Car shows a temp of -32C, hvac set to 18C, 3 fan, both seat warmers on 2 bacon. In 10 minutes, we managed to travel 100m. Average power usage is 5.28kw and an estimated range of 95km... although it would take a whole week to do that at 0.6km/hour. o_O

SPpovdM.jpeg
 

KenC

Active Member
Sep 4, 2018
3,707
3,363
Maine
In survival mode, you wouldn't run the car heater on its normal setting; you'd put it on the minimum necessary. I'd think you'd probably try not turning on the heat, but turn on the seat heater, and carry a blanket or even a sleeping bag. In an emergency pack, there's also one of those aluminized space blanket things to reflect your body heat.

I wonder if one of those heated throw blankets using the car lighter, might not be a bad idea. That would have to be a minimum energy use, heated seat and heated throw blanket. Given the size of the battery, you'd potentially have more energy to run the seat heater and throw blanket, than an ICE would running its engine to heat the whole cabin.

Okay, just checked, the Sunbeam heated throw blanket I have only pulls 70watts.
 

tstolze

Member
Oct 9, 2020
293
423
OFallon, MO
In survival mode, you wouldn't run the car heater on its normal setting; you'd put it on the minimum necessary. I'd think you'd probably try not turning on the heat, but turn on the seat heater, and carry a blanket or even a sleeping bag. In an emergency pack, there's also one of those aluminized space blanket things to reflect your body heat.

I wonder if one of those heated throw blankets using the car lighter, might not be a bad idea. That would have to be a minimum energy use, heated seat and heated throw blanket. Given the size of the battery, you'd potentially have more energy to run the seat heater and throw blanket, than an ICE would running its engine to heat the whole cabin.

Okay, just checked, the Sunbeam heated throw blanket I have only pulls 70watts.

Exactly what I was thinking, same if you're stranded in an ICE, you wouldn't run the engine the entire time.
Warm the car up, shut the engine/heater off, and with heated seats that would likely minimize the time spent heating the entire cabin.
 

GZDongles

Member
Feb 23, 2020
225
283
Michigan
Here's a snippet from a trip I made on the coldest day of the year. Car shows a temp of -32C, hvac set to 18C, 3 fan, both seat warmers on 2 bacon. In 10 minutes, we managed to travel 100m. Average power usage is 5.28kw and an estimated range of 95km... although it would take a whole week to do that at 0.6km/hour. o_O

SPpovdM.jpeg
That's a great data point! If you only went 100m, I think it's probably fair to assume that most of that 5kW was for HVAC and not motion. The car was working against a temperature difference of 50C (-32 ambient heated up to 18 inside), which is probably worse than the worst case most people will ever experience. If someone truly was stuck in the snow, you would turn down heat to a minimum level, or even just use seat heat. So instead of using 7kW constantly, a fair comparison for a true "stuck in the snow" scenario is probably to use ~2kW, or even less if you were in true survival mode and just using the seat heat or cycling the heat on and off. Based on that, you could stay warm for at least 35 hours, and probably double that in a true survival situation!
 

brucet999

Active Member
Mar 12, 2015
2,694
1,500
Huntington Beach, CA
Here's a snippet from a trip I made on the coldest day of the year. Car shows a temp of -32C, hvac set to 18C, 3 fan, both seat warmers on 2 bacon. In 10 minutes, we managed to travel 100m. Average power usage is 5.28kw and an estimated range of 95km... although it would take a whole week to do that at 0.6km/hour. o_O

SPpovdM.jpeg
So, at 5.28 kW average and creeping at .53 km/h, might we assume that heating load consumed maybe 5 kw of that? If so, then it would take 14 hours to use 70 kWh at delta T of 50ºC.
How big is Model 3 battery?
At what SOC does the car shut down cabin heater to conserve battery?
 
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SSedan

Active Member
Jul 24, 2017
2,948
2,328
Greenville Wisconsin
Just for some reference 5kw is 17k btu and change.
I have 12k BTU minisplits heating rooms in my house. Like even my 18x23 living room that is largely glass with 10ft cathedral ceiling near Green Bay and this is a 20yo room on a 40yo house so not super tight like a modern home.

Not going to take 17k btu to keep you alive in a small car interior.
 

M3BlueGeorgia

Active Member
Dec 10, 2018
1,395
1,095
Atlanta, GA
Keep a set of snow chains in the trunk.

Use a blanket.

If worried about battery life while stuck, dial down the temperature. You'll survive for many days with interior temps at 45F / 7C
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,419
12,664
San Diego
It’s about 7kW for the cabin heater at 100% load so if you start at 50% SoC and say it runs at 50% load you could estimate it will last about 10 hours.

35kWh/3.5kW = 10 hours

This is just a quick back of the envelope calculation - there are other things that would likely consume some power at -20F - stator heaters are about 3kW each. But when those would be on is not well understood by me (no experience in SoCal).

Lol @M3BlueGeorgia not sure what there is to disagree with here. This is a factual post indicating how long heat would last at a normal setting set to 73 or so with reasonably high fan speed. Obviously if you were trying to just keep the cabin just above freezing, the battery would last considerably longer as outlined elsewhere here. Nyland came up with 1.5kW, which seems totally reasonable, and he was cold.

The numbers for consumption of the different elements are all pretty close - you can look at SMT videos for those.
 

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