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Is it more efficient to use the recirculate function or the fresh air function when using heating in an EV?

I have a car with a resistive heater, so heat pump behaviour does not come into this.

I would have thought yes, as you are warming already warm air. So the power consumption must be lower. But on the other hand, I am sure most of the losses in the system are through the cold windows and door panels, etc., and the actual mode of recirculation does not benefit us too much. In addition, if recirculate is used, it is necessary to use the A/C occasionally to demist the windows. Most cars now do this automatically, but it will incur additional energy consumption.

Has anyone looked at the physics/data on this to come to a conclusion?
 

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Its better to heat and dry air that is already in the vehicle at this time of year as you will use less energy doing that rather than heating and drying external air.
Yes you lose heat to windows and such, but thats constant anyway.

Personally if its above 10'c i will just have fresh, unheated&non AC air, directed at the windscreen on fan level 2 in my leaf and that keeps the car pretty clear.
Now we are below this i have to use both AC and heat.
Preheating the car helps a lot though.
 

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I noticed that in recirculate mode the windows will mist faster than with fresh air.
The highest power consumption is always at start until the car gets to temperature and then decreases substantially just to maintain it.
You will notice a higher energy consumption in short journeys rather than long ones.
At the end is down to personal circumstances but I would be inclined to say that because EV's can have the heating on while plugged to the charger I would take advantage of that.
For short journeys I would recirculate the air because it will require less initial energy.
On long journeys (+50 miles), if you had the heating on before leaving the consumption in the whole trip won't be as significant.
 

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I noticed that in recirculate mode the windows will mist faster than with fresh air.
The highest power consumption is always at start until the car gets to temperature and then decreases substantially just to maintain it.
You will notice a higher energy consumption in short journeys rather than long ones.
At the end is down to personal circumstances but I would be inclined to say that because EV's can have the heating on while plugged to the charger I would take advantage of that.
For short journeys I would recirculate the air because it will require less initial energy.
On long journeys (+50 miles), if you had the heating on before leaving the consumption in the whole trip won't be as significant.

It will only mist up if you dont have AC on to dry the air out. especially at this time of year.

Also AC is good as just think how much water is getting into the car when you get in while its raining...
 

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Discussion Starter #7
No, you couldn't suffocate, because the vehicle has more vents than the climate control ones. For instance, there are vents usually behind the rear seats. If there were not vents, then the continuous airflow from the outside would become stale too.
 

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Could you suffocate on continuous recirculation, even?

Surely the power saving is trivial although I'm sure it's there.
Nah your eyes would bug out like Arnold Schwarzenegger in Total Recall before you full on suffocate.....ROFLCOPTER!!!!
 

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In a typical car on recirculate, by design, 10% or so of the air is still taken from outside.
 

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In a typical car on recirculate, by design, 10% or so of the air is still taken from outside.
Are you sure? I thought that the recirculate setting was 100 percent so that you can cut off the fumes from the bus in front while you wait at the lights. Then you open up again when the outside air is better.

Since that's all I have ever used it for, I'm probably not too well qualified to comment on continuous use.
 

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though I have noticed my car switches to recirc when starting from cold and I turn on the windscreen demister. Presumably that's to warm the air up quickly.
Interestingly, I note that my Leaf turns off the recirculation when I turn on the windscreen demister.
 

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my car switches to recirc when starting from cold and I turn on the windscreen demister.
my Leaf turns off the recirculation when I turn on the windscreen demister.
Both can be 'right' depending on the external and internal air conditions. Ideally the car will measure the outside and inside temperature and moisture levels and adopt the strategy that works best at that time - and as the conditions change it might alter that strategy.
However, I suspect most cars aren't that clever (I could be wrong) and they just do whatever that manufacturer decides is likely to be right most often.
 

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On a diesel car, in cold weather I'll switch to re-circulate, max heat, max fan and air direction to windscreen only. Then switch to fresh air about a mile up the road. This is on a car with no A/C (Dacia Duster budget jobbie)
 

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As above it should use less energy heating warm air but if your fighting to keep the windows clear outside air is needed. Also, even on cars with air care ect that try to block pollution there is always some air into the cabin for safety reasons.
 
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