Not long ago I wrote a piece on saving money at the pump. Afterwards, a friend of mine noted that I had not mentioned anything about running the car’s air conditioner versus having the windows down as a way to save on gas mileage. The question is does using a car’s A/C use more fuel than having the windows down? The answer, however, was not quite as easy. In fact, there seems to be a complicated debate on equal sides saying one is better than the other.
After some lengthy research on both sides, this is the conclusion I came to. Those on the side of air conditioning argue that the extra fuel usage is minimal; while the loss in aerodynamics with having windows down causes more drag on the vehicle, which in turn uses more gas. Those siding with windows down state that the aerodynamic drag is not significant enough to warrant the extra fuel usage with using A/C. So, who is right? Well, believe it or not, several studies have been conducted on this very experiment. Included in that experiment was a basis of comparison driving a vehicle using a combination of no air conditioning and keeping the windows up. What they found was at low speeds, aerodynamics mean very little, thus having windows down is more fuel efficient. While at highway speeds (60+ mph maintained) there could be enough drag that using the air conditioner is more fuel efficient. Though, this is not as cut and dry as it sounds. Results also depend on the age and type of car. An older car is going to guzzle more gas with the A/C on versus windows down nearly every time. Newer cars are more fuel efficient, and therefore running the A/C has little effect on mileage. In addition, an aerodynamic sports car is going to do better with windows down versus say an SUV.
So, what does all this mean for the average driver? Well, I should first explain that in either scenario, even compared to the car that used neither method of staying cool, the extra fuel usage is minimal at best regardless of driving habits. Beyond that, we must consider age of vehicle, type of vehicle, and how it’s driven (highway or city). Then, make the individual choice of which is better to use. Preferring one way over another is not going to make anyone appear more thrifty even in the long run. So, whether it’s windows down or air conditioning, bottom line, go with whichever feels better to you.