Does leaving the car running with the AC on consume more fuel?

[BrynleeDella]

Leaving the car running with the AC on does consume more fuel. Here is some relevant information about car air conditioning: 1. Introduction to car air conditioning: The car air conditioning system consists of a compressor, condenser, throttle element, evaporator, fan, and necessary control components. It is used to regulate the temperature and humidity inside the car, providing a comfortable environment for the driver. 2. Working principle: When the compressor is running, it sucks in low-temperature, low-pressure gaseous refrigerant from the evaporator. After compression, the temperature and pressure of the refrigerant increase, and it is sent to the condenser. Inside the condenser, the high-temperature, high-pressure gaseous refrigerant transfers heat to the outside air passing through the condenser and liquefies, turning into a liquid. When the liquid refrigerant flows through the throttle device, its temperature and pressure decrease, and it enters the evaporator. Inside the evaporator, the low-temperature, low-pressure liquid refrigerant absorbs heat from the air inside the car passing through the evaporator and evaporates, turning into a gas. The gas is then sucked back into the compressor for the next cycle.

[HadleyLynn]

I've been driving for over a decade and often encounter this situation. Keeping the engine running with the AC on definitely consumes more fuel—the engine has to continuously power the AC compressor, increasing the load and burning extra fuel. I remember one summer when I waited in the car with the AC on for about half an hour under the sun, and the fuel gauge dropped noticeably by around 10%. The reason is that the engine operates inefficiently at idle, and when combined with the AC running at full power, fuel consumption spikes rapidly. To save on costs, I now try to park in shaded areas or parking lots when waiting, turning off the engine and rolling down the windows for ventilation, or simply turning off the AC and using the fan instead. Safety is also crucial—never leave the engine running with the AC on in enclosed spaces like garages, as the risk of carbon monoxide poisoning is too high. Over time, this habit also accelerates engine wear, though regular maintenance like oil changes and carbon deposit cleaning can help mitigate some of the damage. Ultimately, balancing comfort and expense is key.

[RobertLee]

As someone who has worked with cars for many years, I can tell you that running the air conditioning with the engine on definitely consumes more fuel. When the engine is running, it drives the compressor, and this additional energy consumption has to be compensated by burning more fuel, naturally increasing fuel consumption. Simply put, at idle, the engine runs at low RPMs and already consumes more fuel; turning on the AC increases the load, causing fuel to burn even faster. Factors affecting this include how low the AC temperature is set, the engine size (more noticeable in smaller displacement vehicles), and poor efficiency plus higher fuel consumption in high temperatures. I've tested many cars, and idling with the AC on for an hour can use up more than half a liter of extra fuel. My advice: don't do this. When parked, turn off the AC and use natural ventilation or turn off the engine to rest. Regularly maintain the AC filter and cooling system to avoid blockages that could further increase fuel consumption. Safety tip: Never test this in an enclosed space; ensure good ventilation for peace of mind.

[ColeMarie]

I personally care deeply about fuel efficiency and environmental protection. Leaving the engine idling with the air conditioning on indeed wastes fuel and resources. Idling the engine to run the AC increases fuel consumption, costing a few extra dollars per hour in gas money while emitting more exhaust fumes that pollute the air. Just imagine how quickly fuel burns when everyone keeps their AC running during heatwaves—it’s heartbreaking to watch the fuel gauge drop each time. I’ve made it a habit to turn off the engine and roll down the windows during brief stops, or to switch off the AC in advance and use the fan to circulate air instead. This saves fuel and reduces my carbon footprint. If everyone develops good habits, like turning off the engine for short breaks to let in fresh air, it can help protect the Earth’s resources. Over time, both your wallet and the environment will benefit.