A/C verses window wind deflector

No tech data but I believe windows down under 70km/h and up with AC over 70km/h for best economy and the noise is too loud over 75 to 80km/h anyway. You can always crank up the fan and leave the AC off.

 

Would like to install for summer use to air the car out while parked, besides while driving. Any good places to buy?

 

WeatherTech makes deflectors that fit the Prius perfectly. Good quality and easy to install.

 

A few years back I was on a longish summer road-trip in my '97 Honda Prelude, a very aerodynamic car. Even at highway speeds and with the windows and sunroof (I guess it's actually a moon-roof) open, the air turbulence isn't all that bad inside. Anyway, I wondered this same thing and so drove a tankful with windows closed and AC going, and then another tank with windows open and AC off. It got almost 3mpg better mileage with the windows closed and AC on, than with open windows. Can't say for sure how that would translate to a Prius, but suspect that you're better off to run with windows closed at highway speeds.

 

Pearl has the side window deflectors on. I think they look nice. I haven't seen any effect on fuel economy. Got them at the Canadian Toyota dealer. They aren't Weathertech. Only problem has been the foam tape wasn't properly attached to the plastic, from the factory. One came loose gradually, and the dealer got me a replacement set, which I installed. So far the tape has not come off the car, either on the original set or the replacement set. It is still coming off the plastic on the replacement set, though not as bad as the original set.

They are not perfectly quiet on the highway with the windows open an inch or two. It's still quieter with the windows closed and the A/C on. There is no noise from them if the windows are closed. I do leave the windows open an inch or two while parked, and rain doesn't enter, except at the front of the front side windows. It tends to drip in there. Not enough to cause a problem though.

 

I would also agree with that.

Plus the Prius AC is electric so I think I have red it is also more efficient than engine driven AC.

 

Another argument in favor of using A/C at all speeds is that the main (traction) battery and its electronics are cooled by the cabin air. If they get too warm their efficiency drops and fuel economy will be reduced.