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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #1 ·
I'm looking at getting an ID.4 in the relatively near future, and from what I can tell none of the current stock has the optional heat pump. Now, coming from a Zoe driver, I have been thinking a heat pump is pretty necessary. I've read lots of horror stories about older EVs without heat pumps struggling to warm the cabin at all (a problem I don't have in my ZE40). Can anyone tell me whether the standard electric heater will be capable of warming the cabin even on the coldest of UK days? (For reference, I live in the East Midlands, not the Scottish Highlands...) If the heat pump is really just for heating efficiency, rather than heating capacity, I can probably live with it. But I have a lovely wife who insists on being rather warm and toasty on trips, so if the resistive heater will struggle in winter, that might be a deal-breaker...
 

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The resistive heater will be fine.

If anything it's the heat pump that will struggle at lower OATs.

However I suspect the heat pump has a resistive heater as well.
 

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VW ID.3 Worst Edition & Tesla M3 LR
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If the ID.4 is anything like the ID.3, then you’ll find it warms the cabin very quickly.
 

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I can talk to this, I've had three EVs with Heat Pumps and two without and you'll notice the range drop off in Winter more without the heat pump. Back to back I've gone from an MG ZS (without), averaging around 2.7-3.1 miles per kWh during Winter to a Kia Soul EV 3.6-4.1 miles per kWh, both cars are a similar weight and aerodynamically challenged so you can see the difference in energy usage, this makes more of a difference the less battery capacity you have, ironically so the MG range seemed really crap in the Winter, the Soul (I know we are now moving into Spring) already seems indulgent. However both the MG and the e-Golf (the two heat pump less cars) had no problem heating the cabin, the ZS was like an engine furnace, without having auto climate, you constantly do a dance between off and on in that car (or cook like a lobster in a pot if you forget to regulate temperature). So basically, you'll be fine for heat (because its not a Renault), but will see more of a range drop off in Winter.
 

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VW ID.3 Worst Edition & Tesla M3 LR
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On the ID.3, and the ID.4 seems to have the same system, the heat pump isn’t delivering anywhere near the range benefits that some people are expecting.

Next move did a long piece on it;


Edit: Seems the heat pumps are the same;

 

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It really depends on your usage, but I'll try to put some numbers and scenarios out here that give an idea of how much difference it may or may not make to you.

First of all, any EV that has a heat pump ALSO has a resistive heater. The heat pump requires a temperature difference to start operating, so the resistive heater is still fitted in order to "kick start" the heatpump, as well as provide instantaneous heat to defog the windscreen etc.

That means that on a cold day if you come to the car which has been outside overnight and is cold-soaked then both a heat-pump equipped and a non-heat-pump equipped car will use the resistive heater to provide initial warmth and defrost. After approx 3-4 minutes the heatpump vehicle will have enough delta t to move pretty much entirely to the heatpump, and in many uk conditions where you want heating that will have a CoP (Coefficient of Performance) of approximately 3 (ie if you put 500W of energy into the heatpump you will move 1000W of energy from outside to inside, giving you 1500W useful energy output in the cabin).

So, for very short journeys then the difference between the two is irrelevant.

On a longer journey, it's a matter of how much heat it takes to maintain the cabin temperature. On my old Leaf Tekna it tended to be about 500W to maintain 20C setpoint inside when outside was in the 3-5 degree range, once the heatpump was fully into action. In which case, let's assume that the non-heatpump car would require 1500W (going back to that CoP of the heatpump) to maintain the cabin similarly. Over the course of 1 hour then that's an extra kWh required by the non heatpump car. Fairly trivial from a cost standpoint, and a range loss of about 4 miles. If travelling at 50mph then it's an additional 20Wh/mi.

Compared to anecdotal evidence I've seen that seems a bit low, so maybe the true numbers are closer to 1kW for the heatpump vehicle and 3kw for the non-heatpump (ie an additional 40Wh/mi for heating and 8 miles range per hour). It also depends on how well insulated the vehicle is - on the leaf I noticed that the footwells got very cold very fast if the heater was not on, as well as the glass being thinner than other cars I've had. This dictates how much heating power is required to maintain the temperature in the car.

Then the question becomes one of "what is the reason for your concern?". If it's one of cost (ie the additional energy use), it seems unlikely that using a few extra kWh is likely to ever add up to the hundreds of pounds of additional cost for the heatpump. If it's one of range, then that is more valid but when you're looking at larger (ie >50kWh) battery vehicles then the difference of 2-4kWh over a couple of hours of journey is much less relevant that it was with cars like the Zoe 22kWh and Leaf 24kWh.

This line of reasoning is why Tesla went so long without using heatpumps. Aha, you may say, but clearly they were wrong because they're moving to them now?

What tesla have done with the Model Y (and more recent model 3s) is actually a bit more than "added a heatpump". In the Leaf the heatpump was a part of the cabin HVAC system, and it was capable of moving heat to the cabin from the outside world. The Leaf also had a separate radiator and cooling system for the motor and inverter. These were two separate systems. What Tesla have done is to set up a vehicle-wide system that treats heat as a resource - it can move heat from where it is not wanted (eg motor, inverter) to where it is wanted (cabin, battery). If the system has too much heat then it can dump that to outside, if it has too little it can use the heatpump to pull in energy from the outside. It can use motor windings to warm the fluid in the system quickly (eg supercharger pre-conditioning). They combined systems to move heat around, rather than dump heat from one system to outside while using a separate system to warm inside.

So, a very roundabout way to answer your question.

A car with only a resistive heater will be plenty capable of keeping you warm. It will warm up instantly and powerfully (consider sitting in front of a 2kW fan heater in your home). A heat pump system will be more efficient on a longer run, but absolutely requires and relies upon the resistive heater to get it started. On a 5 minute "pop to the shops" journey the difference in energy usage between heatpump and non-heatpump vehicles will be negligible. Over a longer journey it could add 30-40Wh/mi consumption, which will reduce your range and add to your charging time (but in the scheme of a 58kWh or 77kWh battery, it's relatively small potatoes).
 

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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #8 ·
Thanks everyone, sounds like my worries are unfounded and I'll be fine without it!
 

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It really depends on your usage, but I'll try to put some numbers and scenarios out here that give an idea of how much difference it may or may not make to you.

First of all, any EV that has a heat pump ALSO has a resistive heater. The heat pump requires a temperature difference to start operating, so the resistive heater is still fitted in order to "kick start" the heatpump, as well as provide instantaneous heat to defog the windscreen etc.

That means that on a cold day if you come to the car which has been outside overnight and is cold-soaked then both a heat-pump equipped and a non-heat-pump equipped car will use the resistive heater to provide initial warmth and defrost. After approx 3-4 minutes the heatpump vehicle will have enough delta t to move pretty much entirely to the heatpump, and in many uk conditions where you want heating that will have a CoP (Coefficient of Performance) of approximately 3 (ie if you put 500W of energy into the heatpump you will move 1000W of energy from outside to inside, giving you 1500W useful energy output in the cabin).

So, for very short journeys then the difference between the two is irrelevant.

On a longer journey, it's a matter of how much heat it takes to maintain the cabin temperature. On my old Leaf Tekna it tended to be about 500W to maintain 20C setpoint inside when outside was in the 3-5 degree range, once the heatpump was fully into action. In which case, let's assume that the non-heatpump car would require 1500W (going back to that CoP of the heatpump) to maintain the cabin similarly. Over the course of 1 hour then that's an extra kWh required by the non heatpump car. Fairly trivial from a cost standpoint, and a range loss of about 4 miles. If travelling at 50mph then it's an additional 20Wh/mi.

Compared to anecdotal evidence I've seen that seems a bit low, so maybe the true numbers are closer to 1kW for the heatpump vehicle and 3kw for the non-heatpump (ie an additional 40Wh/mi for heating and 8 miles range per hour). It also depends on how well insulated the vehicle is - on the leaf I noticed that the footwells got very cold very fast if the heater was not on, as well as the glass being thinner than other cars I've had. This dictates how much heating power is required to maintain the temperature in the car.

Then the question becomes one of "what is the reason for your concern?". If it's one of cost (ie the additional energy use), it seems unlikely that using a few extra kWh is likely to ever add up to the hundreds of pounds of additional cost for the heatpump. If it's one of range, then that is more valid but when you're looking at larger (ie >50kWh) battery vehicles then the difference of 2-4kWh over a couple of hours of journey is much less relevant that it was with cars like the Zoe 22kWh and Leaf 24kWh.

This line of reasoning is why Tesla went so long without using heatpumps. Aha, you may say, but clearly they were wrong because they're moving to them now?

What tesla have done with the Model Y (and more recent model 3s) is actually a bit more than "added a heatpump". In the Leaf the heatpump was a part of the cabin HVAC system, and it was capable of moving heat to the cabin from the outside world. The Leaf also had a separate radiator and cooling system for the motor and inverter. These were two separate systems. What Tesla have done is to set up a vehicle-wide system that treats heat as a resource - it can move heat from where it is not wanted (eg motor, inverter) to where it is wanted (cabin, battery). If the system has too much heat then it can dump that to outside, if it has too little it can use the heatpump to pull in energy from the outside. It can use motor windings to warm the fluid in the system quickly (eg supercharger pre-conditioning). They combined systems to move heat around, rather than dump heat from one system to outside while using a separate system to warm inside.

So, a very roundabout way to answer your question.

A car with only a resistive heater will be plenty capable of keeping you warm. It will warm up instantly and powerfully (consider sitting in front of a 2kW fan heater in your home). A heat pump system will be more efficient on a longer run, but absolutely requires and relies upon the resistive heater to get it started. On a 5 minute "pop to the shops" journey the difference in energy usage between heatpump and non-heatpump vehicles will be negligible. Over a longer journey it could add 30-40Wh/mi consumption, which will reduce your range and add to your charging time (but in the scheme of a 58kWh or 77kWh battery, it's relatively small potatoes).
Great answer, very comprehensive.

I get the bit about the resistance heater being used to provide fast warmup from a cold start. Not sure I understand why it's needed to bootstrap the heatpump. Maybe someone can explain.
 

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Renault Zoe 50
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Great answer, very comprehensive.

I get the bit about the resistance heater being used to provide fast warmup from a cold start. Not sure I understand why it's needed to bootstrap the heatpump. Maybe someone can explain.
Probably because it means they don’t have to oversize the heat pump for extreme weather.
 
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