How much fuel does it take to run the car air conditioner overnight?
3 Answers
For vehicles with different engine displacements and tuning, the fuel consumption parameters when idling with the air conditioning on vary significantly. According to relevant tests, under one hour of idling with the air conditioning on: a 1.4L Volkswagen Sagitar consumed 2.5 liters of fuel, a 1.8L Honda Civic consumed 4.6 liters, and a 5.0L Range Rover consumed 6.6 liters. Here's the relevant explanation: Running the air conditioning in P gear does increase fuel consumption because the car's air conditioning compressor is driven by the engine. When the engine operates at low speeds, the proportion of power allocated to the air conditioning compressor increases, resulting in higher engine load.
I tested this issue during my last camping trip. My compact SUV consumes about 1.5 liters of fuel per hour when idling with the AC on. For 8 hours, that's a direct drop of 12 liters from the fuel tank. However, it depends on the AC temperature and fan speed. For example, with my settings at 24°C and medium fan speed, if I lower it to 18°C with maximum fan speed, it can consume an additional 0.3 liters per hour. Engine displacement makes a huge difference – my friend's V6 off-roader uses 2.8 liters per hour with AC, while a small car like the Fit only consumes 0.8 liters at 27°C with recirculation mode. With current fuel prices so high, you really need to consider your budget before running AC all night. Buying a car tent might be more economical. Always remember to use it in a ventilated area – enclosed garages are extremely dangerous.
This issue can be broken down into three aspects. First is the engine – in my old 2.0L naturally aspirated car, the RPM instantly jumps to 1000 when the compressor kicks in, then maintains at 850 RPM during operation. With idling AC set at 26°C, the fuel gauge visibly drops one notch per hour. Second depends on temperature settings – during summer when set to low temperatures, the compressor barely stops. My MPV consumed 16 liters in 8 hours with AC at 20°C during 35°C extreme heat. Third is vehicle age – after replacing door seals last year, cooling efficiency improved significantly, saving 15% fuel under same conditions. Most recommended is using bottled water spray for cooling, which is far more fuel-efficient than running AC.
