Now that summer is just about here, the question comes up again.. Assuming that personal comfort was not a factor (lets say someone is equally comfortable with windows open as with the AC on). Obviously I'm not going to drive in hot weather with the windows up and no AC. What is the most efficient way to go? I'm assuming that at 15mph opening the windows is more efficient and at 80mph its going to affect the aerodynamics so much that you would be better off running the AC. But what about all speeds in between?
It could depend on the temp that you set the A/C and how much of the fan you are using, too. If I am traffic, I am not going to subject myself to the secondhand cigarette smoke or diesel fumes. So, my only choice is windows up or if it is hot enough (my threshold personally is 80), turning on the A/C to the lowest setting. I haven't found the gas mileage to suffer with the A/C on that low.
This was discussed before.. can't seem to find it now, but I mentioned before that mythbusters did an episode on this. The professed that the theoretical limit for when you should roll your windows up and use the AC was 50 mph... but then that was on a Suburban which is much less aerodynamic and has a much less efficient ICE and cooling system... so who knows about this car.
I think you can reasonably say based on the data that high speeds use AC and low speeds roll down windows. There's no need to figure out the exact speed that one becomes more efficient than the other because you will make yourself sick with extreme temperature changes. Let's say you roll down the windows at a red light. Then you turn on AC when you get above 45 mph (or whatever speed). Then you roll down windows at the next light. That's an easy way to give yourself a headache. Windows up on freeway. That's all you need to remember.
AC without a doubt. Freeway driving, likely more efficient. City driving likely marginally less efficient but by a very small margin.
AC on in city is probably when you need the AC the most. Not putting the AC on when it's hot, highway or city driving, is one of the "lunatic fringe" aspects of Prius driving. Prius has made the AC very efficient with Eco mode keeping compressor and energy use to a minimum. The effect on mileage is negligible. Guilt free AC.
I live in the South. I can't stand the smell of smoke, nor do I want it drifting into my car. Nothing makes me angrier than when the weather finally gets nice enough to drive with the windows down and the person in front of me is smoking like crazy. I want to enjoy the clean air!
I don't blame you for wanting to enjoy clean air, but I never thought that would be an issue. I would think that the smoke would dissipate before it got to you. I can understand the diesel fumes, but cigarette smoke!
Sit in traffic long enough and any smokers around you will have you hitting the recycled A/C button in a heart beat.
Not here. I think even though we are in the 21st century, and know exactly what the consequences of smoking are, Tobacco was a big industry down here, and to an extent, still is. So, there never is a shortage of smokers, especially in cars because we have ordinances that don't allow for it in public places. Atlanta traffic is some of the worst around and stressed out people seem to smoke more. If only everyone had a Prius...they wouldn't be nearly as stressed out.
Yeah, I tend to get better mileage when I hit traffic on the way home from work, so I'm not as stressed. As a matter of fact I listen to podcasts on the way home, so I don't care if it takes a little longer.
When I'm creeping around (e.g. parking lot) I have the windows open just so I can be amazed at how quiet the car is when it's running on electric only. Only when the sun is beating in and I'm on the highway for hours do I use the AC every so often. Then again our summers are one month long up here, so I'm used to no AC
I believe that was also with all the windows all the way down. Though I think that opening windows on a vehicle that's already not aerodynamic might hurt its efficiency less than one that's more aerodynamic, percentage-wise. When I'm the only one in the car, I usually roll down my window about halfway (less if I'm on the highway), and one or two others to create a breeze. Related question: I've been trying to figure out if it's better aerodynamically to open only one window (driver's) or to open the driver's and one of the others (which? I do not know). If I only open one, the air comes in and has nowhere to escape. If I open two, I'm thinking air would enter in the driver's window and exit through another.
If i am driving windows down, which means it's a perfect day, the windows go on a nd climate control goes on at 70km/h or higher. Deafness is permanent and the noise of an open window at speed can do a lot of damage. It seem this is also a reasonable rule for fuel efficiency also. 70km/h = about 45mph
