Window Down or Air Conditioning: Which Consumes Less Fuel?

In summer, many drivers wonder whether it is better to drive with the air conditioning on or with the windows down to save fuel. Both options result in higher fuel consumption: Open windows increase air resistance, while the air conditioning strains the engine. According to a 2013 SAE study, it is more efficient to drive with open windows up to a speed of about 100 km/h, while above this threshold, air conditioning at 50 percent power is preferable. At highway speeds, e.g., 125 km/h, even full-power air conditioning is more efficient than open windows. However, the results vary depending on the vehicle: For SUVs and sedans, the difference at high speeds is small, especially if the model is not very aerodynamic. It should also be considered that modern air conditioning systems are more efficient than in 2013 when the study was conducted. In summary, it is better to open the windows for short city trips and to turn on the air conditioning for long high-speed drives.