- Air quality
In the summer your air conditioner removes heat from the vehicle, and removes humidity out of the air. Studies show that comfortable drivers are safer drivers. In cooler months, your a/c sytem is back in operation when defrost is selected. The amount of moisture that air can hold changes with temperature. Since cooler air holds less moisture we can defog our windows faster with air conditioning.
A/C can improve the quality of air in the vehicle by removing dust and pollen. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on the evaporator surface. That dust and pollen passing through, stick to its wet surfaces and drain off to the outside of the vehicle through the condensate drain. Air quality is such an important issue to some people, many popular cars models are now being equipped with replaceable cabin air filters.
Fuel Economy* (Not on the list, but worth discussing)
To reach fuel economy goals, manufactures rely on wind tunnel testing. Sleek styling that gives a car its good looks can also help the fuel consumption rating. At highway speeds, wind resistance certainly plays a big part on our fuel economy. Unless your car looks like a brick, you're likely to achive better gas mileage by keeping the windows rolled up. Air conditioning allows us to drive with the windows rolled up.
*Because an air conditioner requires a good chunk of engine horsepower to operate, the fuel saving issue is sometimes arguable. As they say in the advertising business, "your mileage may vary."