How to Minimize Climate Control Energy Use In Summer

[kovalb]

First some background. The LEAF uses a liquid coolant for the motor, inverter, and charger. It also uses this coolant for the heater. There is a resistance heater that warms the coolant. This heater runs most of the time, even when the A/C is running. It warms the cooled air back up to meet the temperature set in the automatic climate control.

Now for how to game the system to maximize range. I live in Phoenix and the days have been about 110° and the mornings between 80° and 90°. After pre-cooling the car, and then starting, I drive until the cabin gets comfortable using a 77° set temperature. After a few miles I turn the set temperature DOWN until the energy usage screen shows a DROP in climate control power. I keep doing this, usually in 2° intervals, each time I see the climate control power rise. This keeps the climate control power down to about 250W (a sliver on the energy usage screen climate control power meter). I am usually down to about a 66° set temperature by the time I get to work, over 30 miles away. In the afternoon I do the same thing but first turn the set temperature up to 80° or 82° to reduce the climate control power after I reach comfort. Then I reduce it as needed.

Turning the climate control set temperature down seems counter-intuitive but it works to keep power minimized. This also works when you are not running the A/C but just want the fan to blow through the vents. Turn the climate control set temperature all the way down to prevent the heater from kicking in and regulate the fan speed manually using the fan buttons.

I hope this helps. It works for me.

 

[Volusiano]

I also live in AZ and have always wondered why everybody says they set their temperature at 75-78F range while I find that I'm comfortably cool enough already when mine is set at 82F. My AC energy indicator usually settles at about 1/3 of the 1.5kw mark and stays constant in that range for the 82F setting. So I guess it's consuming around 500W after it's stabilized.

I thought I was minimizing energy consumption by setting it at 82F. But now if what you say is true, it looks like I've been using more energy with the higher setting due to the heater being on the heat up the cool air to meet my 82F setting.

I wonder why Nissan wouldn't just cycle their AC on/off to meet the desire temperature setting rather than keeping the AC on all the times then use the heater to regulate the temperature on top. This is like the pinnacle of anti-efficiency, especially for a car that's all about energy efficiency. It doesn't make any sense.

 

[TomT]

Might I suggest reading the Service Manual. This is not at all how the heating and A/C system works.

The LEAF uses a liquid coolant for the motor, inverter, and charger. It also uses this coolant for the heater. There is a resistance heater that warms the coolant. This heater runs most of the time, even when the A/C is running. It warms the cooled air back up to meet the temperature set in the automatic climate control.

 

[LEAFfan]

That temp setting (66) would be way too cold for my passenger. Actually, I don't need ANY A/C, but have to use it when someone else is in the car. I'm averaging 5.8m/kW h this month using A/C mostly two days a week for most of the day, including pre-cooling while parked. If the heater were actually being used, I believe the energy meter would show that and it always shows a sliver (-1/-2) after about ten minutes or so with the setting around 83-85.

 

[Volusiano]

Might I suggest reading the Service Manual. This is not at all how the heating and A/C system works.

The LEAF uses a liquid coolant for the motor, inverter, and charger. It also uses this coolant for the heater. There is a resistance heater that warms the coolant. This heater runs most of the time, even when the A/C is running. It warms the cooled air back up to meet the temperature set in the automatic climate control.

Glad to hear AC doesn't use heater. I don't know who to believe anymore. But it makes sense that AC doesn't use the heater.

 

[kovalb]

The heater does run in conjunction with the A/C to achieve the set temperature.
The service manual is meant to assist the techs in... servicing the car. It does not contain every detail of technical information.
If the cabin gets too cool at the low temperature set points, lower the fan speed manually. If still too cool then turn the temp up and live with the increase in climate control power use.
Test out what I say if you don't believe.

 

[TomT]

I have. The PWM resistance heater and the variable speed compressor never run simultaneously except for a very brief period at a transition point. See threads elsewhere here for more details on the hows and whys of the HVAC system... The best way to insure that neither ever run is to turn the temp all the way down and then manually set a desired fan speed.

The heater does run in conjunction with the A/C to achieve the set temperature.

 

[mdh]

I have. The PWM resistance heater and the variable speed compressor never run simultaneously except for a very brief period at a transition point. See threads elsewhere here for more details on the hows and whys of the HVAC system... The best way to insure that neither ever run is to turn the temp all the way down and then manually set a desired fan speed.

The heater does run in conjunction with the A/C to achieve the set temperature.

thanks so much.... just to confirm.. when you say down do you mean it is best to, say, keeping the AC at a low numerical value and control the fan manually? so, 65 degrees uses less energy than 77, for the AC?

thanks again, but just want to confirm.

 

[Volusiano]

The heater does run in conjunction with the A/C to achieve the set temperature.
The service manual is meant to assist the techs in... servicing the car. It does not contain every detail of technical information.
If the cabin gets too cool at the low temperature set points, lower the fan speed manually. If still too cool then turn the temp up and live with the increase in climate control power use.
Test out what I say if you don't believe.

I don't know if you have a source that says the heater is on to adjust the AC temperature or not, or whether it's just an observation that makes you deduce that the heater comes into play with the AC.

But I did test it out on my car and you're right. The higher temp setting indicates higher AC energy use, and if I lower it, the energy indicator drops maybe from around 500w to 250w. I haven't been able to drive it long enough to observe whether I need to keep dropping the temperature setting after a while to maintain the 250w use or not. But every time I up the setting, the energy use goes up, and when lower the setting, the energy use goes down

 

[Nekota]

The heater does run in conjunction with the A/C to achieve the set temperature.
The service manual is meant to assist the techs in... servicing the car. It does not contain every detail of technical information.
If the cabin gets too cool at the low temperature set points, lower the fan speed manually. If still too cool then turn the temp up and live with the increase in climate control power use.
Test out what I say if you don't believe.

I don't know if you have a source that says the heater is on to adjust the AC temperature or not, or whether it's just an observation that makes you deduce that the heater comes into play with the AC.

But I did test it out on my car and you're right. The higher temp setting indicates higher AC energy use, and if I lower it, the energy indicator drops maybe from around 500w to 250w. I haven't been able to drive it long enough to observe whether I need to keep dropping the temperature setting after a while to maintain the 250w use or not. But every time I up the setting, the energy use goes up, and when lower the setting, the energy use goes down

I've noticed that after driving the LEAF during a hot day and then shutting down with power off with the A/C in auto at 80F seems to be cool enough. When I start back up at night when the temperature has dropped down into the 60's the heater turns on to heat up to 80F and I don't notice this until I look at the energy consumption. It seems like there should be a cool down to temperature and a heat up to temperature that have some 'comfort range' between them. I recall some earlier posts recommending to not use Auto A/C due to the heater turning on when temperature moderates. It's easy to notice when the A/C is on but the heater has a slow ramp and high power consumption and no indicator that it's on other than the energy flow NAV panel showing high climate power use.

 

[Volusiano]

The heater does run in conjunction with the A/C to achieve the set temperature.
The service manual is meant to assist the techs in... servicing the car. It does not contain every detail of technical information.
If the cabin gets too cool at the low temperature set points, lower the fan speed manually. If still too cool then turn the temp up and live with the increase in climate control power use.
Test out what I say if you don't believe.

I don't know if you have a source that says the heater is on to adjust the AC temperature or not, or whether it's just an observation that makes you deduce that the heater comes into play with the AC.

But I did test it out on my car and you're right. The higher temp setting indicates higher AC energy use, and if I lower it, the energy indicator drops maybe from around 500w to 250w. I haven't been able to drive it long enough to observe whether I need to keep dropping the temperature setting after a while to maintain the 250w use or not. But every time I up the setting, the energy use goes up, and when lower the setting, the energy use goes down

I got a chance to test this out on a longer drive today. Unfortunately on this test drive, the theory of lowering the temperature setting periodically to minimize energy use (by keeping the heater from turning on) didn't work at all. My AC energy indicator was at 500w most of the times, and it didn't go down to 250w no matter how much I lowered the temperature setting. It was a bit hotter today than my other test drive yesterday, and the trip is also 4 times longer.

So, I'm not so sure if I've turned 100% believer or not.

I still really want to know whether the OP got his theory (that the heater is used in conjunction with AC) through observation or from a reliable technical source somewhere.

 

[smkettner]

I would like to see someone put a clamp on ammeter to the heating coil circuit then put it through its paces to see when the current is flowing.
Until then I plan to just use the auto button and set temp to 74-72.

 

[ecoobsessive]

Is there a chance that the heater runs at the same time as the A/C when the "auto" button is on, but not when "auto" is off and just the A/C button is on???

 

[aqn]

[...] After a few miles I turn the set temperature DOWN until the energy usage screen shows a DROP in climate control power.

The higher temp setting indicates higher AC energy use, and if I lower it, the energy indicator drops maybe from around 500w to 250w.

Personally, I am highly skeptical of the "energy used by climate control" display. As you may know, we've had a record number of days over 100' here in Central Texas this year. I've had many opportunities and many different scenarios of air conditioning usage. I have come to the conclusion that the "energy used by climate control" display could be a big fat liar just like the Guess-O-Meter.

One behavior that has been about 75% reproducible over a handful of times so far is merely turning off the climate control (button under <strike>A/C button</strike> edit: "AUTO" button) and turning it back on (i.e. no other changes) lowers the "energy used by climate control" figure. For example, a reading of 3+ kWh will read 1.25-1.5 kWh after cycling the climate control button; a 1.5 kWh might read 0.3-0.5 kWh afterwards. This happens regardless of whether I'm moving or not.

I have no explanation for that behavior, only that it has been more reproducible than not.

 

[palmermd]

It was bugging me earlier in the spring, and this was my solution...

http://www.mynissanleaf.com/viewtopic.php?p=110129#p110129" onclick="window.open(this.href);return false;

I plan to install a switch and a relay in the circuit if I need the heater this winter, but I'm adding heated seats, and I don't expect that I'll miss the factory heater at all. Perhaps later model cars no longer have this issue.

I'm certain the heater was coming on when I was only trying to run the AC, because the heater has a distinctive smell, and I saw my guess-o-meter dive each time it happened. It happens real fast because it draws lots of current trying to heat the water in the system up before you ever notice it in the cabin.

 

[Volusiano]

I'm certain the heater was coming on when I was only trying to run the AC, because the heater has a distinctive smell, and I saw my guess-o-meter dive each time it happened. It happens real fast because it draws lots of current trying to heat the water in the system up before you ever notice it in the cabin.

Why would you say heat the water in the system up? Because I thought the heater heats up the air coming into the cabin. The only water system I know about is the cooling system for the inverter and charger.

I never smell any distinctive heater smell in my car yet, and I've never had to actually use the heater (only had the car since June in AZ), so I wouldn't know what it smells like yet if the heater has never been turned on yet.

I'm still not sure whether the heater turns on during AC use in my car yet. At least there hasn't been any obvious indication.

 

[Herm]

The heater in the Leaf uses water, its adapted from a standard BEV heating system.. the Volt uses a similar system. Not sure you would smell the antifreeze solution since its not a pressurized system like ICE cars use... no microscopic leaks for you to smell.

How come no Leaf owner ever talks about using electrically heated vest and gloves?.. very common in the motorcycle world. Its not a lot of power, 200watts in a vest would roast you.. and its instant heat.

 

[palmermd]

Not sure you would smell the antifreeze solution since its not a pressurized system like ICE cars use... no microscopic leaks for you to smell.

The smell is more like the smell of cooking dirt. The dust that collects on the heater core begins to get hot, and that is the smell I'm referring to. Same as almost every auto heater.

 

[TomT]

Guys, the HVAC system is covered in excruciating detail in the service manual. Read it and most of your questions will be answered. The manual is the best 20 bucks you will spend on the car!

 

[dgpcolorado]

...How come no Leaf owner ever talks about using electrically heated vest and gloves?.. very common in the motorcycle world. Its not a lot of power, 200watts in a vest would roast you.. and its instant heat.

Not being a motorcycle rider, I've never heard of such a thing but it sounds like a good idea for those of us with real winters. They don't even seem to be very expensive. Great suggestion!