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What Uses More Gas – Rolling Down the Windows or Using Your Air Conditioner?

April 13th, 2009

conserve-gas-windows-air-conditioner.jpgSure, we all love to do our part to help out humanity, but isn’t it always best when being selfless also lets you be selfish? Like when volunteering to donate blood gets you out of the office for a few hours, or offering to be the parent who takes all the kids to the park lets you go to the ice cream shop (just because the kids like it, of course). Could it be that rolling up your car windows and basking in the cool, refreshing breeze of air conditioning is actually helping use less gas? Well, yes. And no.

This is one of those questions full of “maybes” and “it depends.” In general, the theory is that in city driving it’s more efficient to roll your windows down, but at highway speeds open windows create tremendous drag so you’ll actually use less fuel rolling them up and turning on the air conditioning. At least that’s the theory — but as with so many other things, the devil is in the details. Just take a look at the diversity of opinions:

  1. Consumer Reports says that drivers should try to avoid using the air conditioner at speeds below 40 mph, but above that the air conditioner makes more sense.
  2. The Florida Solar Energy Center conducted a test and found that with a Volkswagen GTI at 65 MPH the increase in consumption was 3% with the windows down, whereas with the air conditioning on it was 12%.
  3. In an Edmunds.com test conducted at a steady 65 miles per hour, “windows down” or “A/C on” made virtually no difference in mileage.
  4. Grist Magazine claims opening your windows will decrease your fuel efficiency by about 2 to 3 percent, whereas the air conditioner will cut it about 15 percent.
  5. The Mythbusters television show ran a computer simulation that showed it’s more efficient to keep the windows up and run the A/C. Then they ran a real world test… and completely contradicted the computer simulation.

The problem is there are so many variables: every car has different aerodynamics, wind direction and speed vary, and air conditioners work harder – thus use more gasoline – on hotter days. So when faced with an almost unanswerable question, the best solution might be to take the middle course; in the city try to keep the windows down and the air conditioner off, and on the highway put the windows up and turn on the air. Of course the best solution of all, temperature permitting, is to leave the windows up and simply open the vents.

Last thing - if you do use the air conditioner, a few tips:

  1. The air conditioner uses gas but the fan doesn’t. Best to have the temperature set to a moderate position and the fan on high.
  2. If available, set the vents to recirculate the air within the car - it’s more efficient than trying to cool the hot outside air.
  3. If your car has been sitting in the sun get rid of all the hot air first - roll down the windows for the first few minutes of driving before putting them back up and turning on the air conditioner.


About the Author

Mark Fradl is a writer for Constant Content who has sold a total of 11 articles covering a variety of topics. If you are the author of this article and would like to include additional information in this section or submit other articles for publication here at Karlonia.com, you can do so through the Contact page.


2 Responses to “What Uses More Gas – Rolling Down the Windows or Using Your Air Conditioner?”

  1. comment number 1 by: repairman23

    This was the common doubt many of them have. Thanks for your reviews on this topic.

  2. comment number 2 by: mplo

    It’s true that a car air-conditioner does cut down on fuel mileage somewhat. The best thing to do, however, is to have the A/C of one’s car turned down as low as one can tolerate it. Simply opening up the window presents some problems too, however; It can let all the hot, stale air into your car, and bring unwanted insects in with it, to boot.

    Regarding home A/C’s, however, everybody wants to crank their A/C’s on “High” during a heat wave. That’s a problem, because it puts more strain on the grid. I often keep my A/C on Low or Medium when I’m home and at night, even if I do end up sweating a little more. However, when I leave my apartment for any length of time, I turn the A/C onto the Energy Saver mode.

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