Using a vehicle’s air-conditioning system increases fuel consumption. Most vehicle air conditioners (AC) require engine power to operate. Of all auxiliary power requirements, AC system use has the greatest impact on fuel consumption.
Automobile manufacturers are developing more efficient AC system technologies and control strategies to reduce the impact of an AC system on fuel consumption. For example, some manufacturers have introduced electric AC systems to improve vehicle fuel efficiency.
Using the AC can increase fuel consumption by up to 20% because of the extra load on the engine. The AC load depends on the vehicle’s interior size, the outdoor temperature and other operating conditions.
Running your air conditioner does cause your vehicle to consume more fuel, but driving with your windows rolled down can be even worse due to the increase of drag on the vehicle.
According to James Bertrand, who heads the thermal systems division at Delphi Corporation, one of the world’s largest automotive suppliers, “a car uses less fuel to run an air-conditioning system than it will use due to the aerodynamic drag on a vehicle when its windows are open”.
Your car’s air conditioner is an important accessory, it’s operated by your engine and places an additional load on your engine when it’s running.
However, don’t switch on the AC immediately after starting the engine, run it for a minimum 1km with slightly open windows to let the inside heat go and then close windows and switch on the AC, also keep the blower in 1 when alone and increase it to II or III when travelling.