How much fuel does a car consume when idling with the AC on?
4 Answers
When a car is idling with the AC on, it consumes approximately 0.8 liters of fuel per hour. Here are the details: Car air conditioning: It refers to the air conditioning device installed in a car, which can cool, heat, ventilate, and purify the air inside the cabin, providing a comfortable environment for passengers, reducing driver fatigue, and improving driving safety. The air conditioning system has become one of the indicators to measure whether a car is fully equipped. Components of the air conditioning system: Generally, it includes a cooling device, heating device, and ventilation device. This integrated system makes full use of the limited space inside the car, featuring a simple structure and easy operation, making it a popular modern car air conditioning system internationally.
That day I specifically tested it, and idling with the AC on does consume fuel. My 2.0L car burned about 1.5L of fuel in one hour with the AC on while stationary, and it was even more exaggerated when running at full blast under the summer sun. The AC compressor is driven by the engine, which already consumes fuel at idle, and adding the compressor's workload is like making someone run in place while carrying a backpack. Frequent AC cycling in city traffic can increase fuel consumption by 2L per 100km, and being stuck in traffic for half an hour can burn as much fuel as driving 7-8km. Also, I noticed that the exhaust smell is particularly noticeable when waiting with the AC on, so I recommend not doing this in underground garages to avoid carbon monoxide poisoning.
We car modifiers often test this data. A 1.6L naturally aspirated car idling with AC on consumes 1.2-1.8L of fuel per hour, depending on compressor power and temperature settings. Last time I tested a friend's 3.0T - with automatic AC set at 24°C and music playing, it drank nearly half a tank in two hours. Cars with auto start-stop save some fuel, but the annoying part is the compressor stops working during engine-off periods, blowing hot air. The key factor is coolant temperature - poor cooling makes the fan work harder, consuming extra fuel, especially noticeable in older cars. Vehicles with variable displacement compressors perform much better, as their power adjusts with temperature, unlike old-school compressors that always run at full power when engaged.
I've measured the fuel consumption when idling with AC on. For a family sedan with a 1.5L engine running AC at 25°C, it burns roughly a can of Coke's worth of fuel in half an hour. The principle is straightforward: the engine consumes fuel to maintain idle operation, while the AC compressor diverts some of that power. It's like standing still while running an electric fan – of course it's going to consume electricity. The hotter the weather, the more fuel it consumes because the compressor has to work harder to cool. I've seen people turn off the AC and just use the fan, which only consumes a tiny amount of fuel to power the blower, but that's completely ineffective in summer – the hot air feels like a sauna.
