How much fuel does a car consume when idling with the AC on for one hour?
3 Answers
When a car idles with the air conditioning on for one hour, it consumes approximately 2 liters of fuel. Below is an introduction to engine idling: The engine primarily maintains the operation of the air conditioning compressor, water pump, oil pump, flywheel, etc. If the clutch is engaged (without pressing the clutch pedal), the engine also drives components such as the input shaft gears of the transmission. Engine idling consumes a significant amount of fuel, as it only powers the air conditioning compressor, leading to higher energy consumption. Prolonged operation at high temperatures may also result in carbon dioxide buildup.
As a veteran driver who often takes breaks during long-distance trips, I've found that idling with the AC on for an hour consumes varying amounts of fuel, typically between 1 to 2 liters. For instance, my older sedan uses about 1.2 liters per hour when idling with AC, while an SUV exceeds 1.5 liters due to increased compressor load and higher engine RPM. Fuel efficiency is already poor when the engine isn't moving, and running the AC makes it worse—the hotter the temperature and the lower the AC setting, the more fuel is consumed. This habit not only wastes money but also increases emissions and harms the environment. I recommend using a mobile app to monitor usage or parking in shaded areas to reduce AC runtime. Regularly cleaning the AC filter can also improve efficiency and save some fuel.
I've worked on quite a few cars and know a thing or two. Idling with the AC on consumes about 0.8 to 2 liters of fuel per hour. The key factors are engine displacement and AC settings; smaller engines with less compressor activity can go as low as half a liter, while larger engines at full cooling might exceed 2 liters. Idling already keeps the engine running at minimal efficiency, and turning on the AC adds extra load, burning fuel faster. Over time, this can lead to carbon buildup and part damage. It's best to use recirculation mode to minimize cool air loss. On hot days, I often advise against prolonged AC use for comfort—portable fans are more eco-friendly and cost-effective.
