How to use the air conditioner w/o compromising fuel efficiency..Live in South Florida

sweet! i'm always wondering when the a/c comes on and when it doesn't.

 

I was hoping that it would do the opposite -- take air from the coolest available source, not hottest.

 

Yeah it should compare inside to outside temp, and when you first turn it on, if the outside air is cooler than the car (usually is), then run the fan high, but *do not* engage recirc until it cools off. This will also help push the hot air out the back. Then, once the inside is cooler than outside, it should switch to recirc until the car is at the set temp, then it can occasionally switch to fresh (or as needed to cool the pack). Staying in recirc on hot days most of the time will use less energy.

 

This is called a "total enthalpy" calculation. From an air conditioning standpoint, the latent heat in air is both temperature and humidity. Generally there is less total enthalpy in the cabin air, even on a hot day. This is because the small volume of cabin air is quickly cooled and dried, whereas the external air keeps coming in hot and humid, having essentially an infinite volume.

The Prius A/C control does a pretty good job picking the least expensive way to cool the cabin. It's not perfect, but it's pretty good.

Tom