It has been stifling hot this summer (thanks, Global Warming) even in our usually temperate climate of Vancouver.  We’ve been hitting 30+ degrees Celsius regularly (about 86+ degrees Farenheit for youngandthrifty’s USA friends).  My boyfriend and I are known to be really cheap when it comes to turning on the air conditioning, but in this hot hot heat, we’ve been less stingy and have been closing the windows and pressing that button and turning on the glorious A/C.

Because of this hot heat, and possibly because I was rendered delirious from the heat, it got me wondering, which one IS cheaper for fuel economy? Air conditioning or having the windows down?  Which one will help that tank of gas (running at $1.18/L again here in Vancouver) go that extra mile for you?

There are two camps to this often heated and long drawn debate, probably not dissimilar to the pronouncement of tomato.  To-MAY-to or To-MAH-to. =)  That is the question.

Camp A/C is pro Air Conditioning (I guess that was self explanatory) and believe that using air conditioning will help you with your fuel economy because drag occurs when your windows are rolled down.  This drag (aka wind resistance) slows down the car, and causes the engine to have to work that much harder, hence lowering the fuel economy.  It’s all about the aerodynamics, baby.

Camp windows down is all for leaving the windows down and letting that wind caress the face and give to them that beautiful wind-tousled hair. They feel that because the car has to work extra hard to cool the heated air coming from the outside, this will affect fuel economy to a large extent (anywhere from 3-20%, it is at the higher end for a really hot day).

Mythbusters (this awesome show on the Discovery Channel that experiments- very scientifically, I might add- the most common myths and either approves or disproves them) did a segment on whether using air conditioning or rolling the windows down is cheaper.  They even re-tested this myth again just to make sure in a later episode.  They subjected this myth to much rigorous testing, and the conclusion was…. (drum roll, please)

Leave the windows down for city driving (anywhere from under 50MPH, which is about 80km/h), but once you drive faster and you’re on the highway, you should roll the windows up and turn on the air conditioning.

How Stuff Works (another great show I love) also wrote about this hot topic, and came to the same conclusion (but with a varied “cut off” speed, they said 40MPH, not 50MPH).

Here are some tips that might also help you save a few bucks on your fuel economy and also help the environment too:

  • make sure you change the air filter regularly (a clogged air filter makes the car work that much harder to cool the air in your car)
  • clump up your errands to locations that are close to each other (I love doing this, either I’m lazy, or I’m eco-friendly, you be the judge)
  • drive when it’s cooler out (perhaps do your grocery shopping in the early evening, when it’s not so hot)
  • If you can, cycle or take transit or get a scooter (much cheaper and eco-friendly options compared running a 1 tonne car when it’s only just little ol’ you sitting in it)
  • Once you do get the AC on, try to keep the air circulating (there’s that button that recirculates the air in your car, press it), instead of having your car cool down air each time

Of course, you can make your own decisions as to whether you would like to keep the windows down or roll them up and turn on the AC.  Sometimes turning on the AC on is necessary to keep everyone happy, cool, and non-irritable, and can be invaluable on those long road trips (especially with fussy children- though I cannot speak on my own behalf as I have never had children yet).

I personally am still (and always will be) a windows down person, I do like the wind in my hair, even on the highway sometimes, but will keep in mind to turn on the AC next time I’m going on a road trip.

Readers, are you a windows down or an AC driver?  Have you found any difference between the fuel economy of the two yourself?