What is the fuel consumption when idling with the air conditioning on?
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. Below are the four cyclic processes of a car's air conditioning system: 1. Compression process: The compressor draws in low-temperature, low-pressure refrigerant gas from the evaporator outlet and compresses it into high-temperature, high-pressure gas before discharging it. 2. Heat dissipation process: The high-temperature, high-pressure superheated refrigerant gas enters the condenser, where it condenses into a liquid due to the reduction in pressure and temperature, releasing a significant amount of heat. 3. Throttling process: The higher-temperature and higher-pressure refrigerant liquid passes through the expansion device, where its volume increases, and its pressure and temperature drop sharply, exiting as a mist (fine droplets). 4. Heat absorption process: The mist-like refrigerant liquid enters the evaporator. Since the boiling point of the refrigerant is much lower than the temperature inside the evaporator, the refrigerant liquid evaporates into gas, absorbing a large amount of surrounding heat in the process. The low-temperature, low-pressure refrigerant vapor then re-enters the compressor. These processes repeat continuously to achieve the cooling of the air around the evaporator.
I understand how the car system works. When you run the air conditioning in neutral, the engine is idling and doesn't need to drive the wheels, but the AC compressor increases the engine load, leading to additional fuel consumption. Typically, this consumes an extra 0.2 to 0.5 liters of fuel per hour, depending on your car's engine size, AC settings, and ambient temperature. For example, a 1.6L car running the AC on a hot day might burn an additional 0.3 liters of fuel. This is a waste of resources because the engine already consumes base fuel in neutral, and adding the AC makes the fuel tank deplete faster. Additionally, this increases exhaust emissions, which is bad for the environment, and may also lead to engine carbon buildup or reduced component lifespan. In daily driving, I recommend using the AC only while driving, as this balances the engine load better, optimizes fuel consumption, and reduces unnecessary costs.
