Resistance heater actual amperage draw?

Sorry if this has been covered, I did not find it in my searches; wondering if the resistance heater (2015 Leaf S base model) draws the same amperage when it is on, independent of the fan, or is the heater also proportional like the fan? and what is it's draw in amps ( I assume 12V?)? Also, how do the steering wheel and seat heaters compare in terms of amperage? Thanks all,...

The resistance (aka PTC) heater is NOT 12 volt. It uses high voltage from the pack, and it draws a lot of amperage. The car displays energy usage in kilowatts, and IIRC the PTC maxes out at about 3kw. I think it can throttle back a little, but I'm not actually sure - both of my Leafs had had the heat pump as well, and that affects the current draw at any given moment. I'd find it hard to believe that the PTC always runs at maximum, regardless of fan speed (the blower is 12 volt) and cabin air temperatures.

The seat and steering wheel heaters are 12 volt, and don't draw a lot of power. They are what you want to use to reduce heater use.

http://www.nissantechnicianinfo.mobi/htmlversions/2013_EV_Special/Climate_Control.html

On my 2012SL, I've seen the onscreen climate control dial as high as 5.5kw for heat. Hopefully, models with the newer heat pump system will see less. On the plus side, I do get lots of heat and pretty quickly. Just can't go anywhere beyond about 35 miles.

SalisburySam said:

On my 2012SL, I've seen the onscreen climate control dial as high as 5.5kw for heat. Hopefully, models with the newer heat pump system will see less. On the plus side, I do get lots of heat and pretty quickly. Just can't go anywhere beyond about 35 miles.

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Heat pump-equipped Leafs do draw that much, because the PTC operates in tandem with the heat pump, but they quickly throttle back (except maybe in frigid temps) to 1.5kw or less. I've seen as little as 500 watts.

2011 Leaf (resistance heat).

I have seen the heater use as much as 4.5 or 5 kW. When the AC button is turned on, the energy use can rise another .5 to 1 kW. I don't know if this is because it increases the power to the heater or because the compressor actually runs at the same time to defrost.

Actual power draw depends on a number of factors. The temperature inside the car, the temperature outside, the temperature of the heating coolant loop, AC button, and the fan speed all play a factor. I've noticed that selecting defrost tends to increase the power consumption. Likewise, higher fan speeds will call for more heating power.

As the car and the heating liquid heats up, the power consumption of the heater will begin to drop. It tends to equalize around 1.5 kW in 20-30F temps.

I don't believe Leafs after 2012 have a heating liquid loop. I believe they have a direct PTC heater. This may cause the behavior to change.

Finally, when the car is plugged in, it will not exceed the input power from the charger. On L1, this is around 1.5kW. L2 is 3.3 kW or 6.6 kW depending on the on board charger. Heat while plugged in only works if the car has a climate control temp timer enabled and the car is started by holding the brake while pushing the power button or the climate timer triggers.

Preheating the car while plugged in has been incredibly helpful. You can preheat not only the car but also the heating coolant, meaning that the battery never sees the high initial power draw.

Go to the energy info screen and play around. You can see the real-time power output of your car.

I have seen the heater use as much as 4.5 or 5 kW. When the AC button is turned on, the energy use can rise another .5 to 1 kW. I don't know if this is because it increases the power to the heater or because the compressor actually runs at the same time to defrost.

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The compressor actually runs at the same time, to dry the air. In the "hybrid" system, when heat and defrost or heat and A/C are both engaged, the heat pump provides the A/C and the PTC heater provides all the heat. That makes the combination a real energy hog.

I don't believe Leafs after 2012 have a heating liquid loop. I believe they have a direct PTC heater. This may cause the behavior to change.

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Correct. From 2013 on the heating is all direct to air - no coolant/heatant loop other than the one inside the heat pump.

Finally, when the car is plugged in, it will not exceed the input power from the charger. On L1, this is around 1.5kW. L2 is 3.3 kW or 6.6 kW depending on the on board charger. Heat while plugged in only works if the car has a climate control temp timer enabled and the car is started by holding the brake while pushing the power button or the climate timer triggers.

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Hmmm... My understanding is that the car will draw full heating power, because all Leafs power their heaters and A/C or heat pumps directly from the battery pack. The power provided by the EVSE will either fail to match the power drawn, resulting in dropping charge level, just match it (no change in charge level) or will exceed it (car keeps adding charge, albeit more slowly). I know this. The only thing I'm not certain of is whether or not the coolant loop systems in the 2011-2012 cars have the heat-limiting feature you mention. I know that 2013+ Leafs do not.

Thanks all, this is great info. I do not seem to have a KW meter on-screen, the model S is the base model, unless I am missing something? That info would be really helpful.......

dmacarthur said:

Thanks all, this is great info. I do not seem to have a KW meter on-screen, the model S is the base model, unless I am missing something? That info would be really helpful.......

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Don’t feel bad about this...from this thread and all the posters you now know what the actual behavior is even if you don’t have a display to show you. And like any vehicle, you’ll quickly get used to what happens without thinking about it. Enjoy your car, and the knowledge that you know how it works.

LeftieBiker said:

Hmmm... My understanding is that the car will draw full heating power, because all Leafs power their heaters and A/C or heat pumps directly from the battery pack. The power provided by the EVSE will either fail to match the power drawn, resulting in dropping charge level, just match it (no change in charge level) or will exceed it (car keeps adding charge, albeit more slowly). I know this. The only thing I'm not certain of is whether or not the coolant loop systems in the 2011-2012 cars have the heat-limiting feature you mention. I know that 2013+ Leafs do not.

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Interesting. I can confirm on my 2011 that when on L1 charging, heat output is limited to approximately 1000-1200W when the car is ON (but not in ready mode) and connected to L1 charging. This roughly matches the input power from the L1 charger. It will maintain this power output basically indefinitely to warm the car in the morning, until I unplug the car and put it in ready to drive mode. In Ready to drive, it will provide full heat output (as much as is necessary based on internal/outside temperatures, etc).

It's interesting to hear that this behavior doesn't exist on the 2013+ Leaf's. This feature is really nice for L1, because it won't discharge my battery during pre-heating, even if I pre-heat for 15-30 minutes.

dmacarthur said:

Thanks all, this is great info. I do not seem to have a KW meter on-screen, the model S is the base model, unless I am missing something? That info would be really helpful.......

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On my 2011, it's under Menu->Energy Info. It's possible this doesn't exist on the smaller screen model (S model in 2013). You can get the same info from LeafSpy under the power consumption screen--it shows up as "climate control".

Lothsahn said:

Interesting. I can confirm on my 2011 that when on L1 charging, heat output is limited to approximately 1000-1200W when the car is ON (but not in ready mode) and connected to L1 charging. This roughly matches the input power from the L1 charger.

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This is definitely not true for me on L2; don't know why it would be different than L1, but there it is.
That's why if/when I pre-heat (which isn't often) I usually give it > 15 minutes or I end up with a (slightly) reduced charge.

The liquid coolant heater in my 2011would draw up to its full-rated power (about 5 kW) when pre-heating while plugged in on L2 (never tried L1, but probably the same) so it would discharge the battery for a bit until coolant temperature increased enough to cause the power draw to be reduced. I always pre-heated for at least an hour to make sure the car was warm, coolant loop was hot, and battery was fully charged (by 3.3-kW charger) when starting my commute on a cool "winter" morning.

The PTC heater in my 2015 will also draw up to its full-rated power of about 5 kW under certain conditions, but tapers off faster than the liquid heater in the 2011. The heat pump power draw is much lower unless the set point temperature is high enough for the controller to decide that resistance heat is needed.

I played with our 13 leaf S yesterday, it was 20F outside. With the fan on 4 temp set to 90F the car ramped up to 4000w then after about 5 minutes dropped to 3500w. I switched the fan speed to 1 leaving it set to 90F and it dropped to 1000w after afew minutes. Then I turned the fan back up to 4 and the wattage creeped back up to 3000w. It appears to step in 250w or so steps. I believe basically it heats up the elements but with a low fan speed the core warms up and steps down wattage. I would image if it was colder outside it would draw more power at a given fan speed to keep the core at a given temp and warmer outside and it would consume a lower wattage.

Oddly enough I did swap back and forth between normal and eco more and it never changed the power consumption.

If I turn the temperature all the way down and drive in eco mode mine will run at under 500 watts, blow out luke warm air and stay pretty cold in the car, definitely not 60F.

SageBrush said:

http://www.nissantechnicianinfo.mobi/htmlversions/2013_EV_Special/Climate_Control.html

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I read through most of the link and it's quite interesting technical detail. I'm wondering though if the PTC heater for 2018 and newer is more efficient than 2013-2017? If so, then what would be typical energy use difference under the same heater use conditions?

I have a colleague who bought a non all weather 2018 and I was comparing it to my all weather 2018. Under the same weather conditions (30 F) it appears his heater power usage was only about 30 pct more than mine. Albeit not totally scientific as we were not closely monitoring the kW usage, but the range impact when the heater was engaged.

jdcbomb said:

I'm wondering though if the PTC heater for 2018 and newer is more efficient than 2013-2017?

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All resistance heaters have the same efficiency

SageBrush said:

jdcbomb said:

I'm wondering though if the PTC heater for 2018 and newer is more efficient than 2013-2017?

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All resistance heaters have the same efficiency

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Yes and no. All resistance heaters are rated "100% efficient" because any losses are in the form of heat, and thus get added back into the total. But if you compare, say, a baseboard electric radiator with a good fan-forced heater, you'll realize that some heaters are much more efficient at heating larger areas. I've gone through many electric space heaters over the years, and some have been great at heating with a 900 watt input or less, while others have sucked using 1500 watts - they just create a small bubble of hot air around themselves, while the air 10' away from them is too cool. I use electric radiators as well, and just putting a small fan in front of one will greatly boost its effectiveness. (Depending on the thermostat setting, it may also increase the energy used.) So just because all resistance heaters are 100% efficient at converting electricity into heat, don't assume that they all work equally well at heating an area for a given energy input.

While I think that the air to air PTC heater in the 2018 Leaf is likely the same efficiency as it was (and quite likely the same actual unit), the HVAC system as a whole could be a little more effective, and thus more efficient, at heating the cabin with less energy.

LeftieBiker said:

SageBrush said:

jdcbomb said:

I'm wondering though if the PTC heater for 2018 and newer is more efficient than 2013-2017?

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All resistance heaters have the same efficiency

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Yes and no.
While I think that the air to air PTC heater in the 2018 Leaf is likely the same efficiency as it was (and quite likely the same actual unit), the HVAC system as a whole could be a little more effective, and thus more efficient, at heating the cabin with less energy.

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You are saying that the heat may be distributed differently. I suppose, but that is not an efficiency measure.

And of course nothing prevents you from tuning the fan in a car, or directing the hot air where you want it to go.
No matter, a kWh of electricity is turned into a kWh of heat.

What I am saying is that some heaters use more energy to heat the same area thoroughly, because while they are 100% efficient at converting an electric current to BTUs, they vary widely in how well they distribute that heat. Since the PTC is just one element of the Leaf's HVAC system, with the blower being another, I think it's unlikely the PTC is more efficient, but possible that the HVAC system as a whole was improved a little. AFAIK the 2018's HVAC system is unchanged - except that you can now use Recirculate in Floor + Defrost mode. That alone could be the difference in effectiveness...