AC or Windows Down? Which One Is Better for Fuel Economy?

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?

28 Comments

  1. Mich@BeatingTheIndex on August 23, 2010 at 10:57 am

    I’ve always wondered about these 2 cases: A/C or windows down. Thanks for finally clearing things up for me 🙂



  2. Echo on August 23, 2010 at 11:11 am

    Ahh, the great A/C debate 🙂

    For us the choice is easy, my wife has MS and suffers terribly if it’s too hot. A/C is always on in the car, and we installed it in our house this Spring after an unbearable summer last year. I don’t want to sacrifice health to save a few bucks.



  3. young on August 23, 2010 at 11:15 am

    @Mich- You’re welcome! I’ve always wondered too. =)

    @Echo- Your wife has MS? =( Glad to hear she is supported so well by her loving husband! =) Yes, no one should ever sacrifice health to save a few bucks!



  4. Tiny Potato on August 23, 2010 at 9:31 pm

    I’ve heard some people only fill up the gas tank half way to save gas by not driving around the weight of an extra half tank of gas.



  5. young on August 23, 2010 at 9:34 pm

    @Tiny Potato- Haha! I’ve heard that too, actually. I wonder if they should disprove that on Mythbusters…. =)



  6. The Passive Income Earner on August 23, 2010 at 9:36 pm

    I am an AC driver. The smell of other cars while driving in the city is not worth trying to save a penny



  7. young on August 23, 2010 at 9:38 pm

    @The Passive Income Earner- I guess it depends on how the air quality is that day too! So many factors to think about…=) I personally really like the sensation of wind blowing…but I do sometimes like the controlled climate of AC, too.



  8. Kevin@InvestItWisely on August 24, 2010 at 7:02 pm

    “Leave the windows down for city driving (anywhere from under 50MPH, which is about 80km/h), but once you drive faster and you



  9. young on August 24, 2010 at 7:17 pm

    @Kevin- me too! I sometimes like sweating too, but not too uncomfortably.. as long as the sun doesn’t burn through my skin, I do like warmer muggier weather.



  10. Little House on August 24, 2010 at 7:19 pm

    I



  11. young on August 24, 2010 at 7:22 pm

    @Little House- I say you, me, and Kevin @Invest It Wisely go for a car ride with the top down. =) Yeah, I hear San Fran is quite cool too (though you’re quite a ways away from San Fran).



  12. Financial Samurai on August 24, 2010 at 11:38 pm

    I like this tip below! It’s always pretty cool in SF, so the windows are always down in the city, and up on highway on econ mode!

    Leave the windows down for city driving (anywhere from under 50MPH, which is about 80km/h), but once you drive faster and you



  13. Kay Lynn @ Bucksome Boomer on August 25, 2010 at 4:49 am

    My windows are always up because my car because i use the feature to keep the inside temperature constant.

    However, my daily commute is only 3 miles so I don’t think it would be a big difference if I rolled the windows down.



  14. young on August 25, 2010 at 7:02 am

    @Bucksome Boomer- 3 miles?? Very jealous! Yeah, I don’t think it would make a difference too. I guess it’s something to keep in mind on longer road trips. =)



  15. young on August 25, 2010 at 7:03 am

    @Financial Samurai- Yeah, you guys get that nice San Fran breeze! =)



  16. Money Reasons on August 25, 2010 at 7:11 am

    Nice job, I especially appreciate the Myth Buster



  17. young on August 25, 2010 at 7:14 am

    @Money Reasons- Your A/C in your home, right? What method did you end up using? =)



  18. Khaleef @ KNS Financial on August 25, 2010 at 7:36 am

    Great article! I’ve always wondered which was more efficient.

    I’m like you, I love the wind blowing against my face, and I will rarely turn on the a/c. Like Echo, my wife has health problems that are made worse by the heat, so that’s the only time it comes on.



  19. young on August 25, 2010 at 7:54 am

    @Khaleef- Nice to meet another devoted husband! =) Glad you liked my article. That question was bugging me so I decided to finally put an end to my endless pondering. =)

      Thanks for visiting!


  20. Money Reasons on August 25, 2010 at 9:19 am

    My heat pump in my house broke last year (that did bite hard!).

    My car A/C broke last year (and still is). It probably just need a recharge, but the nozzle is in a difficult place to get to, so I’m not able to do it. Had I know that this summer would be as hot as it was though… I would have fixed it in spring!!!



  21. young on August 25, 2010 at 8:06 pm

    @Money Reasons- lol, sometimes wish we had a crystal ball eh? Does the Farmers Almanac help? Had most people known here last winter that there would be no snow, I’m sure they wouldn’t have spend $700+ on their seasons passes (glad I didn’t!). Guess you could always get it fixed next spring. =)



  22. Financial Cents on August 27, 2010 at 8:32 am

    @Money Reasons – I’m too cheap as well. My A/C went in my 10-year-old car in mid-summer. Not worth getting fixed with only another month to go. Next year!

    (Besides, I like hanging my head out of the window like a puppy while driving 🙂



  23. Objectif 0 on October 14, 2010 at 6:16 am

    when I’m in the convertible, it’s windows.. and top down!
    but in the truck, it’s usually windows up. Plus I like the comfort of not hearing the outside world and not have to turn the radio volume up.



  24. eemusings on February 28, 2011 at 6:52 pm

    That’s great! will have to bear this in mind for our road trip this weekend.



  25. young on February 28, 2011 at 10:47 pm

    @eemusings- Ooh! Have a great road trip! Where are you going?



  26. Dino on November 17, 2011 at 11:18 pm

    Yes the great debate on a/c windows up or down. The Mythbusters did prove it and I tried it well before the did and while your driving in the city or under 80/km/hr keep the windows down and above 80 windows up and on with the a/c . But I also have a rebutle to this debate as well, guess wha most people don’t know is that turn your defrost on and crank the fan and guess what…….it blows cool air without using the a/c and you still get your great gas mileage whle enjoying a cool breeze with the windows up. Don’t believe me try it.



  27. young on November 20, 2011 at 11:28 pm

    @Dino- Cool! I will give that a try next time- though its winter now and I don’t think I need to turn the A/C on yet!



  28. I.Bailey@Air conditioning las vegas on March 23, 2012 at 6:38 am

    Great info. I think you should turn off your window of the car when you have to on your air conditioner because if you did so then your car have to take extra load. In this way your engine may take much pressure on itself. And all things happen due to the aerodynamics. Aerodynamics manages ups and downs related to this.



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