Using air conditioning (A/C) in your vehicle does increase fuel consumption. When the A/C is turned on, the engine must work harder to power the compressor, which reduces fuel efficiency[1][2][3]. The effect can be quite significant, especially in hot weather: running the A/C can reduce a conventional vehicle’s fuel economy by up to 25%, particularly during short trips or in stop-and-go traffic[1][2][6][8].
Several variables influence how much extra fuel is used, such as outside temperature, humidity, vehicle type, and driving conditions. The impact is usually greater in city driving than on the highway since the engine speed fluctuates more in urban environments[1]. Larger vehicles or vehicles with bigger engines typically require more energy to cool larger cabin spaces[3]. Even with newer, more efficient systems, air conditioning still requires power from the engine[3].
If you turn off the A/C, you reduce the load on the engine, which can improve fuel efficiency[1][5]. For those looking to save fuel, consider using the A/C conservatively, such as cooling the car initially, then using the ventilation system or rolling down the windows when driving at lower speeds[3]. However, keep in mind that at higher speeds, opening windows can also increase aerodynamic drag and hurt fuel efficiency, though usually not as much as using A/C in extreme heat[7].
References
- [1] Does AC Affect Gas Mileage? – AutoZone.com
- [2] Fuel Economy in Hot Weather | Department of Energy
- [3] Does my AC really affect my gas mileage? – Plymouth Rock Assurance
- [5] How to Affordably Run Your Car’s Air Conditioning – Chapel Hill Tire
- [6] A/C vs. MPG: Does Your Car A/C Use Gas Or Electricity?
- [7] Saving fuel: Windows down or air con on, which is better?
- [8] Does Air Conditioning Affect Fuel Economy? – Peoria – Beachlers