How much fuel is consumed by idling with the air conditioning on for one hour?
2 Answers
Idling with the air conditioning on consumes approximately 1.4-2.5 liters of fuel depending on the engine displacement, with an average of around 1.6 liters. While the fuel consumption is not excessive, it is detrimental to the engine, as it can lead to carbon buildup and overheating damage to the catalytic converter. Additional details are as follows: 1. Idling: This refers to the engine running without any load, only overcoming the internal friction of its components, without delivering power externally. The minimum stable speed at which the engine operates under these conditions is called idle speed, one of the five fundamental operating states of an engine. Adjusting idle speed should avoid sudden increases or decreases in RPM, as this can cause premature wear on the engine. 2. During engine idling: The engine not only powers the air conditioning but also maintains the normal operation of the power steering and brake booster pumps, though these functions are unnecessary when the vehicle is stationary. The sole reason for idling while parked is to keep the air conditioning running and ensure comfort inside the vehicle. In fact, idling offers no benefits to the vehicle. Prolonged operation at low RPM can lead to carbon buildup, which over time may cause unstable idling and affect the engine's power performance, as well as its lifespan. Moreover, when idling while parked, due to lower air flow, the combustion efficiency at low RPM is not high, resulting in significantly higher emissions compared to normal driving conditions.
Having driven for thirty years, I think idling with the AC on for an hour consumes between one to two liters of fuel, depending on the car model—small cars save a bit, while SUVs use more. Turning on the AC increases the engine's load due to the compressor, so higher fuel consumption is inevitable. One summer, I waited by the roadside for an hour, and the fuel gauge dropped noticeably. Doing this long-term not only wastes fuel but also causes carbon buildup, damaging the engine. I recommend avoiding this—if you must wait, crack the windows or turn off the AC. The extra fuel cost is roughly ten yuan per hour, and it adds up over time. Also, a safety reminder: idling in a garage risks carbon monoxide poisoning. During peak summer heat, the AC puts more strain on the engine, increasing fuel consumption even further. Alternatively, try turning on the AC at a lower fan speed after starting the car to slightly reduce fuel use, or use an app to ventilate the car in advance—both can help.
