How Much More Fuel Does Your Car Use With the Air Conditioner On?

On a hot summer day, turning on the air conditioner feels almost mandatory. But many drivers also wonder the same thing: how much extra fuel does it actually use?

The simple answer is that yes, air conditioning increases fuel consumption, but usually not by as much as many people think.

The air conditioning system is powered by a compressor connected to the engine. Whenever the compressor is running, the engine has to work a little harder, and that requires more fuel. The exact increase depends on several factors, including the outside temperature, the type of vehicle, and how hard the air conditioner has to work.

For most modern gasoline and diesel cars, fuel consumption typically increases by 3–10% when the air conditioning is in regular use. In city driving, where speeds are lower and the engine already works less efficiently, the increase can sometimes be even more noticeable. On the highway, the extra fuel used by the air conditioner is often relatively small compared to the total fuel consumption.

Electric vehicles are different. Instead of using more fuel, the air conditioner draws electricity from the battery. This means the driving range can decrease, especially during extremely hot weather when the cooling system is working continuously.

Many people wonder whether it is better to drive with the windows open instead. At lower speeds, opening the windows may save a little energy. However, at highway speeds, open windows create additional aerodynamic drag, which also increases energy consumption. In many cases, using the air conditioner with the windows closed becomes the more efficient option once you are driving at higher speeds.

The best approach is to use the air conditioner wisely. Parking in the shade, using a windshield sunshade, and ventilating the car for a minute before starting your trip can reduce the amount of cooling needed. This helps keep both you and your passengers comfortable while minimizing the extra energy your vehicle has to use.