Yes, a car's air conditioner does consume fuel. The air conditioning system in a vehicle is driven by the engine, and it requires energy to operate. When you turn on the A/C, it engages the compressor, which puts an additional load on the engine. This extra load requires the engine to burn more fuel to compensate for the power needed to run the A/C system.
The amount of fuel consumed by the air conditioner varies depending on various factors, including the outside temperature, the A/C setting, the efficiency of the A/C system, and the driving conditions. In general, using the air conditioner can decrease a car's fuel efficiency by a few miles per gallon, especially in stop-and-go traffic or during hot weather when the A/C is working harder to cool the cabin.
If maximizing fuel efficiency is a priority, you can reduce the A/C usage or use the A/C system more efficiently. For example, at lower speeds or when parked, you can rely on the car's ventilation system to circulate fresh air without engaging the A/C compressor. Additionally, keeping the windows closed while using the A/C can help improve fuel efficiency by reducing drag. However, in extremely hot weather or during extended driving, using the A/C for comfort may be necessary, even if it slightly decreases fuel efficiency.