Is the defogger really that bad?

[acl]

It's that time of year when the windscreen is misted up in the morning so I put the demister on to clear it. My fan is usually set to 22C with auto and I only do it to clear the screen when it happens and turn it off when the screen is clear. But I notice that my power consumption ROCKETS to something like 30kw/100km as opposed to 16kw/100km when its off and it totally ruins the tripmeter measurements. How is it that a simple fan and heater can nearly double the power consumption of the car like this? Is this simply a glitch in the way the consumption being measured, a fault in my car or completely normal?

 

[dsimpkins]

It is normal, as you are using electricity from the car's main battery to run the heater. One of the reasons why the range on an EV decreases in Winter. An ICE car uses the heat from the engine and its coolant system to heat the cabin so its range is less affected by colder weather.

 

[acl]

I'm not disputing it uses energy, but the fact that it uses practically the same energy to blow some hot air on a windscreen as it does to propel a 1700kg car just seems weird. It didn't use anything like the same energy to run the AC during the summer months.

 

[fnegroni]

the GoM will also be affected
My take is that your average speed will influence the guess-o-meter’s opinion of the impact of running an extra 2-3 kW appliance over the distance and in the time you are covering it.
So say you drive in heavy traffic, covering 10 km averaging 10km/h.
The motor will consume say 2 to 3 kWh but the heater and a/c combined will also consume 2 to 3 kWh on that journey.
So the GoM is going to report just that: 6kWh for 10 km

obviously the A/c and the heater are not on all the time, which is why the peak of 30kWh for 100km makes sense when they are working full time at the start of the journey.

The example above was an exaggeration but I noticed it takes the GoM and the average power consumption numbers at least 5km to stabilise

 

[dsimpkins]

Agreed. On a short journey such as commute to work, I can see GoM reporting 2.3 miles/kWh, but on longer journeys it is closer to what I see in summer. On long journeys its more like 3.4-3.6 miles/kWh at this time of year, but in the summer I was seeing around 4.0 miles/kWh.

 

[Ian Key]

The heater uses a constant amount of energy until the car is warmed up. The car only uses energy when accelerating and with regen the average amount of power used could be the same as the heater especially over a short journey as the heater will be on all the time.
On a longer journey once the heater has warmed the air and fabric of the car the heater will switch on and off as required so reducing its consumption but the amount of energy used by the car will be about the same as the shorter journey.

 

[Eber]

The SE doesn't have a heat pump. So generating heat is VERY inefficient. The entire cabin has to be warmed up and this will consume a lot of energy since the cold air in the car will continually cool down the heater element.

It's like in the pub. You will consume more beer in the first hour than before going home.

 

[Rolfe]

I note that if I run the pre-heat routine on the car when the battery is at 100%, by the time it's done the SoC has dropped to 98%. In ten minutes!

 

[JonnyG]

Try giving the glass a good clean and using Rain X Anti Fog or similar. I’ve done this on my front and back screen and it helps a lot. Also keep AC on all the time if range is not a concern.

 

[hharzel]

It is certainly normal. When A/C is on at the start of journey, the consumption goes to 29.8kWh per 100km and stays there for a while until it starts slowly dropping. If the trip is long enough, it will eventually settle to around 17-20kWh depending on how you drive, at about 0 degrees celsius.

 

[tsedge]

AC must be on for a fast defog, since it takes the moisture out of the air, also make sure all the air is going up the screen for fastest defogging.

Yes, heating takes huge amounts of energy - if we all switched to electric home heating it would use many times the energy it would take to electrify transportation.

If you look at your gas bill, you'll see the energy you use in gas (converted to kWh) dwarfs your electricity bill, even if you have an EV or 2.

Heat pumps are different, they are pretty efficient but even they use a large amount of electricity to run, which surprises some people when they get one.

 

[MoDolph]

The heating is the worst thing about the car in my opinion. My previous leaf would keep us warm for a few hundred Watts, the MG4 blasts through multiple kW of power and still my feet are always cold.

 

[Rolfe]

Did the Leaf have a heat pump?

I tend to think, well, if it takes 2% of the battery to pre-heat the car, that's 1 KWh. How much is that? 28p without a variable tariff? Imagine it as coins in my hand. Am I bothered? Not a lot.

Do you have the heating set to the footwell? I don't have this problem of cold feet.

 

[lsp01]

Dear all

I'm planning to do some tests about how heating works (and even the AC being on/off) during winter temperatures

This is about SE, so without heat pump.

I'm interested to know if the resistor producing heat has only one power level or not, and if it is on continuously or not. And try to see how the power consumption depend on the temperature and fan settings.

I'm also curious if AC in winter has any interest. On my petrol cars, it greatly helps with defogging.

Of you can share any knowledge you've got related to this topic would be great thanks

 

[Rolfe]

I've merged a new post into this thread so we can keep all the information and advice in the same place.

 

[Anon70]

Some tips on Winter driving from Burl Solomons that might be of interest

 

[tsedge]

But I have the bug where you cannot preheat if plugged in and not charging. Now I know I can start a charge and then do it (fine for 80% LRers), but does anyone know if this bug is fixed yet?

 

[siteguru]

Supposedly it has been - I recall reading here somewhere that someone got an update which fixed it. I can't recall whom it was though.

 

[Diggsy]

Regarding the power usage when the heating is on, I need to do some more testing, but I noticed the other day that my wife had set the blower to ‘4’ and temp to 23 or 24. No matter what way I was driving the car, the guess o meter barely touched 3. I changed back to my normal ‘auto’ and 25 setting yesterday and was not only easily getting 3, but almost got to 4 at one point.

It leaves me wondering if it’s the blower speed that is the main power drain. More testing needed…

 

[mg4mc]

But I have the bug where you cannot preheat if plugged in and not charging. Now I know I can start a charge and then do it (fine for 80% LRers), but does anyone know if this bug is fixed yet?

Works for me. On Saturday morning the car was at 100% with the cable still plugged from the overnight charge.

I switched on the "Preconditioning" in the charger to provide power and switched on both battery and cabin heating in the car. The car was then drawing the full 7 kW from the charger whilst it warmed up.