Best way to run AC in the summer.

Well, air conditioning time is upon us in the Okanagan. Typically we just select auto and set for 24 degrees. Is this the most efficient way or is there a better manual method.

Thanks in advance.

John and Angela.

If you want to save energy, as opposed to cooling the car to the set temp fast, do it manually, with fresh air intake until the car is at or just below the outside temp, with the blower on "3" or so, and high-low selected for the vents. When the car gets to the outside temp, close the Recirculate control and change the vent setting to just the dash vents, and when you are comfortable enough, lower the blower speed to 2 or even 1. Make sure the temp control isn't set too low. If you'd like some fresh air, try using partial/automatic Recirculate, by pressing that button and holding it 2 seconds while it's in Recirculate more. The indicator light on the button will flash twice and go out if you are successful. This mixes in 30% fresh air, if I remember correctly. Pulling in all fresh air uses more power, and using all recirculated air uses the least power once the air is cooled.

LeftieBiker said:

If you want to save energy, as opposed to cooling the car to the set temp fast, do it manually, with fresh air intake until the car is at or just below the outside temp, with the blower on "3" or so, and high-low selected for the vents. When the car gets to the outside temp, close the Recirculate control and change the vent setting to just the dash vents, and when you are comfortable enough, lower the blower speed to 2 or even 1. Make sure the temp control isn't set too low. If you'd like some fresh air, try using partial/automatic Recirculate, by pressing that button and holding it 2 seconds while it's in Recirculate more. The indicator light on the button will flash twice and go out if you are successful. This mixes in 30% fresh air, if I remember correctly. Pulling in all fresh air uses more power, and using all recirculated air uses the least power once the air is cooled.

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Thanks Leftie. We have been selecting AC, 24 degrees and recirc. So if I understand you and assuming we want to cool the air, this is the most efficient manner. How does “auto” effect things.

Thanks.

The Auto setting runs the blower on high to cool the hot car fast, which maxes out the energy consumption.

Thanks again Leftie. We may be in Canada but the Okanagan Valley can get pretty hot. We were in the car for a couple hours today. Even with the AC though, when we were done we had travelled 152 km and there was about 50 left on the GOM. Mostly between 70 and 90 Km per hour though except for about 40 km of 105 km/h the or so.

By the way, we saw the new red (like yours) in a 2018. Very nice. It’ll be a tossup between white and red on our 2020 long range.

Cheers.

I agree with some of Leftie's advice ..

Look for shade
Use a sun-screen
Crack open windows if possible for ventilation when car is parked
Cool interior to ambient when starting out on a drive.

Then...
Set you preferred Temp and use Auto. In the car (Prius) I know best, the AC controls humidity by varying admixture with the outside as needed and varies the compressor and fan speeds for best efficiency. I am no AC expert but my understanding is that matching fan to compressor work load is the important parameter. I'm giving Nissan the benefit of the doubt here that they know as well as Toyota how to program the AUTO AC.

I usually come up with ~ 0.5 - 1 kW AC load at steady state, so about 5 - 10 Wh a Km. Not bad really, although I do not live in a high humidity environment. The improvement in Aerodynamics in hotter weather usually more than compensates for my AC use and I end up getting better fuel economy in the summer than other times of the year. Complaints typically come from owners with short trips who let their cars turn into greenhouses while parked. Then the AC is working at 5 kW the entire trip.

For another way to figure things, once you are at a steady state temperature the work of AC in heat removal (humidity is extra) approximates to solar radiance. If we figure 1-2 meter squared and 45-90 incidence angle and 1000 watts per square meter, the load is between 700 - 2000 watts. Since the AC COP is probably around 3 the electricity consumption works out 230 - 700 watts.

Thank you for your input sagebrush.