How much fuel is consumed when idling with the air conditioning on for 3 hours?
4 Answers
Idling with the air conditioning on for 3 hours consumes approximately 3-4.5 liters of fuel. Below is relevant information: Air conditioning: The air conditioning system mainly consists of components such as the compressor, expansion valve, condenser, evaporator, and blower. Cold air is produced by pressurizing the compressor to liquefy the refrigerant, which then vaporizes, absorbing heat from the air to achieve a cooling effect. Using air conditioning in winter: The warm air used in winter mainly comes from the engine, so it does not consume much fuel. However, summer is different; using the cold air function will definitely consume more fuel. During idling: The vehicle consumes about 2 liters of fuel per hour while idling because the engine is in an idle state with low RPM, resulting in reduced air intake efficiency. Besides fuel consumption and carbon buildup, idling also causes certain environmental pollution.
My own car is a 1.5L sedan, and I usually don't idle with the AC on. But that one time during summer when I was stuck in traffic for three hours, I decided to test it. At idle, the engine runs at around 800 RPM, consuming about 0.7 liters of fuel per hour. With the AC compressor on, it increases by approximately 0.3 liters per hour, totaling 1 liter per hour. Over three hours, that's about 3 liters. This is considered a moderate level—larger displacement SUVs might double that. I think doing this not only wastes money but also leads to carbon buildup and engine damage, and the AC compressor is prone to excessive wear. I recommend avoiding idling with the AC on unnecessarily; it's better to park and rest somewhere. If you must use it, keep it under half an hour and regularly check the battery voltage to avoid draining it.
Having worked on various cars, the fuel consumption from idling with the air conditioning on for three hours varies greatly. For small cars with a 1.0-liter engine, it might be around 0.5-0.8 liters per hour, plus an additional 0.2-0.4 liters per hour for the air conditioning, totaling less than 1 liter per hour. Mid-size SUVs with engines above 2.0 liters can consume 1-1.5 liters per hour at idle, and with the air conditioning adding 0.3-0.6 liters per hour, three hours could burn 4.5-6.3 liters. Many factors influence this: the efficiency of the engine cooling system, the air conditioning temperature setting, fan speed, and even outdoor temperature. At its peak, it might reach over 7 liters, which is still within the normal range. I must warn that this practice is harmful to the car and dangerous, with risks of engine overheating or carbon monoxide leakage. It's advisable not to exceed one hour and to regularly maintain the fuel system to reduce wear and tear.
In the early years, I drove an old-style van and often idled with the air conditioning on. After three hours, the fuel consumption was astonishing, at least 1.2 liters per hour, with the AC accounting for 30%, totaling over 3.6 liters. Newer cars with smaller displacements might cut that in half, but it’s still wasteful. Over time, the engine accumulates more carbon deposits, and black smoke comes out of the exhaust pipe. I’ve had the experience of a dead battery stranding me, so now I’ve learned to use this method less. In the summer heat, it’s best to park in the shade, turn off the engine to rest, or use a portable fan instead. If you really need the AC, start it for shorter periods, like 15 minutes at a time, which saves fuel and protects the battery.
