Q: How Much Does Using the AC Affect Fuel Economy

There are several variables that will influence the answer to that. It depends on your vehicle, how you drive, where you drive, and how hot it is outside. But there are some things that are certain: operating an A/C system does require extra energy.

Simply turning the A/C compressor on requires several horsepower from your engine that would otherwise be used to move your car down the road. There goes some gas money. A bit more electricity is required when operating the A/C and blower fan, so the alternator has to work harder. There goes some more gas money.

A frequently overlooked factor is the fact that driving with A/C turned off usually means the windows are open, making the vehicle less aerodynamic. A vehicle with the A/C on and the windows closed is more aerodynamic, thus consuming less fuel pushing through the air.

I suggest you do a test to find out what the impact of A/C operation is on your own vehicle’s fuel economy in hot weather. Monitor your gas mileage over a typical warm week without using the A/C. Then check your mileage for a warm week while using the A/C whenever you drive. You will likely see a small difference. If you are even able to complete the test, that is! Trying to drive without A/C in hot weather may convince you that it is so worth it that you will no longer care about the 1.5mpg penalty.

Should you run into any problems with your A/C, feel free to reach out to a certified mechanic that can diagnose and make any repairs necessary to fix your air conditioner.