How much fuel does a car consume when idling with the air conditioning on for one hour?

[JeremiahAnn]

When a car idles with the air conditioning on for one hour, it consumes approximately 2 liters of fuel. The engine's operation primarily maintains the functioning of the air conditioning compressor, water pump, oil pump, flywheel, etc. If the clutch is engaged (the clutch pedal is not pressed), the engine also drives the gears of the transmission input shaft and other components, making idling quite fuel-intensive. Below are some methods to reduce fuel consumption: 1. Check the air conditioning system in summer: Air conditioning malfunctions are a significant cause of high fuel consumption. Poor cooling performance may lead to increased fan speed and lower temperature settings to achieve a comfortable cooling effect. 2. Frequent hard braking: Frequent hard braking is a major factor contributing to high fuel consumption. While ensuring safe driving, make full use of the vehicle's inertia. 3. Avoid excessive air conditioning in small-displacement cars: For vehicles exposed to the sun, avoid turning on the air conditioning immediately after entering. First, open the windows and set the fan to a higher speed without turning on the air conditioning to expel the hot air inside. Once the car has cooled down moderately, then turn on the air conditioning.

[LukeFitz]

I tested my old 1.6L sedan with the AC on at idle speed during the hottest midday in summer. With maximum cooling fan speed, it burns about 1.2 liters of fuel per hour. When gas price was 8 yuan per liter, I calculated it costs roughly 10 yuan per hour just for AC. A 2.0T SUV would consume even more - my friend's new car measured over 2 liters. I'd advise against prolonged idling with AC on - it hurts both your wallet (fuel cost) and the engine (carbon buildup), plus exhaust fumes accumulating under the car pose safety risks. If you must wait with AC on, park in shade, use external air circulation mode, and lower fan speed to save some fuel.

[IsabelDella]

Idle fuel consumption with AC on mainly depends on engine displacement and AC power. My decade-old compact car was tested: with the auto AC set at 25°C in summer and the compressor cycling on and off, the displayed fuel consumption was about 1.8L per hour. However, using the heater in winter is more fuel-efficient since it utilizes waste heat from the engine, consuming less than 0.8L per hour. Note that aftermarket high-power car refrigerators or audio systems can significantly increase fuel consumption. I've seen cases where installing a car coffee maker pushed idle AC fuel consumption close to 3L.

[AutumnAnn]

Actual measurements under different conditions: When a small-displacement car runs its air conditioning compressor at full load in summer, the idle fuel consumption is about 1.5-2.5L/hour. The key factor is the compressor's operating time ratio—it consumes the most fuel when the car is just started. After the temperature drops, intermittent compressor operation can save about one-third of the fuel. Small devices like seat ventilation or charging a phone have minimal impact on fuel consumption. However, with more electric vehicles now, air conditioning mainly uses electricity, making this aspect less cost-effective for fuel-powered cars.