How much fuel is consumed by idling with the air conditioner on for one hour?
3 Answers
Idling with the air conditioner on for one hour consumes approximately 2 liters of fuel. The engine's rotation primarily maintains the operation of the air conditioning compressor, water pump, oil pump, flywheel, etc. If the clutch is engaged during idling (without pressing the clutch pedal), the engine also drives the gears of the transmission input shaft and other components. The fuel consumption when idling with the air conditioner on depends on the vehicle's displacement and engine tuning. Of course, idling for extended periods mainly increases fuel consumption and causes engine carbon buildup, so it is recommended to avoid keeping the car in standby mode for too long. In idle mode, turning on the heating air conditioner does not cause serious harm to the car, but it can affect the occupants. When the engine is idling, incomplete fuel combustion produces carbon monoxide. If the windows are closed, the concentration of carbon monoxide inside the car will gradually increase, potentially leading to carbon monoxide poisoning for the occupants.
As a driver with over 20 years of experience, I can tell you that idling with the AC on for an hour consumes a significant amount of fuel. Specifically, a typical sedan can burn 1.5 to 2.5 liters of fuel, while larger SUVs or luxury cars may consume over 3 liters, depending on engine displacement and AC settings. During summer heat, the AC compressor works at full capacity, placing greater load on the idling engine and increasing fuel consumption; winter is slightly better, but still not negligible. This doesn’t just hit your wallet—it also causes wear on the engine and battery. I recommend avoiding prolonged idling with the AC on. Exceeding 30 minutes is wasteful; turning off the engine when parked is safer and saves money. Switching to a fan or parking in the shade can save you enough for several meals each month.
In the maintenance industry, I often help car owners inspect their air conditioning systems. Running the AC while idling for an hour typically consumes about 1 to 3 liters of fuel. The air conditioning relies on the engine to drive the compressor, and at idle speed, the engine runs at low RPM with lower energy conversion efficiency, causing fuel consumption to spike due to the additional load. Smaller car engines consume less fuel, starting at around 1 liter, while larger or older vehicles may double that amount. Key factors also include the AC temperature setting and external temperatures—running the AC at lower settings on hot days consumes more fuel. To save costs, it's recommended to regularly maintain the AC filter, as clogs can increase the load. When parked, try to turn off the engine and open windows for ventilation; this habit can protect the vehicle's longevity in the long run.
