We’ve had this question asked a few times recently and decided to investigate it. Which method of driving is more efficient; driving with your windows down and AC off or driving with your windows up and AC on? Today we find out
Which Is More Efficient, Windows Down Or A/C On?
Testing the effect of both methods (windows down, AC off versus windows up and AC on) has been done and debated by several different organizations. One of the leading groups, the Society of Automotive Engineers, conducted a number of tests on the effects of AC versus windows rolled down on automobiles.
The SAE found that running an air conditioner in an automobile decreased gas mileage by 5 to 10%. Stanford University and SAE both recommend driving with your car’s windows down if you are traveling on city streets. However, when on a freeway or highway, the drag produced by your windows being rolled down exceeds the efficiency drop by keeping windows rolled up and AC on. Both organizations recommend that you use your car’s AC when driving at speeds above 45 MPH.
With that in mind, it’s probably best to do your driving in the early morning or later at night when possible. This is when the day is (usually) cooler. Driving with the A/C off and windows up is the most fuel efficient way to operate your automobile.