How Much Fuel is Consumed When Idling with Air Conditioning On for One Hour?
3 Answers
Leaving the car idling with the air conditioning on for one hour consumes approximately 2 liters of fuel. Below is relevant information about car idling: 1. The function of car idling: Idling is an operational state of a car where the engine runs in neutral gear. The engine speed during idling is referred to as the idle speed. The idle speed can be adjusted by modifying the throttle opening size. Idling means the engine is 'producing power without doing work.' When the engine is running, if the accelerator pedal is completely released, the engine enters the idling state. 2. Causes of unstable idling: Direct causes include dirty, worn, or incorrectly installed mechanical parts, leading to variations in cylinder power output, which results in an imbalance of power among cylinders and causes unstable idling. Indirect causes involve abnormalities in the engine's electronic control system, leading to poor combustion of the air-fuel mixture, making it difficult to balance the power among cylinders and resulting in unstable idling.
Last week while getting my car repaired, I happened to test the AC fuel consumption of several vehicles. A 1.6L Corolla burned 1.2L of fuel per hour with the AC idling, while a 3.0L Highlander could reach 2.8L. Actually, it's not just about engine displacement - setting the AC to its lowest temperature versus 26°C can make a 0.5L difference in fuel consumption. I once met a BMW owner who installed an OBD scanner and found that with auto start-stop enabled, the compressor shuts off more frequently, saving 30% more fuel compared to older models. My suggestion is to turn off the engine if waiting exceeds 15 minutes - it saves fuel and prevents carbon buildup.
My engineer friend explained this: The compressor consumes 10%-15% of the engine's power. Taking a 2.0T engine as an example, the idle fuel consumption is about 1.8 liters/hour, meaning the air conditioning alone consumes 0.2-0.3 liters. However, the actual calculation should also include the power consumption of the blower, especially when the maximum fan speed is used, which increases the generator load. Summer tests on a hybrid Accord showed an air conditioning power consumption rate of 1.8 kWh/hour, equivalent to about 0.15 liters of gasoline—ironically, the hybrid system is more efficient in this scenario.
