When it’s cold and you can’t see out of your car’s windshield, you probably reach for the defroster. But how does the defroster work? And why does it always take so long for ice, frost, fog or mist to disappear from your windshield?

Learn all about how car defrosters, demister and anti-condensation systems work.

There are two primary types of defrosters. The first type uses a vehicle’s heating, ventilation, and air conditioning (HVAC) systems to blow warm, dehumidified air directly onto a fogged or iced-over windshield. The other type of defrost system defogs and defrosts through a mechanism known as resistance heating.

Defrosters that use a vehicle's HVAC system are sometimes called "primary" defrosters because they are designed to clean the windshield and side windows. They work on two main principles.