The defrosting system eliminates the build-up of ice (frost) in the refrigerator and freezer.

Too much ice formation reduces the storage space available in a refrigerator and also reduces its cooling efficiency. All refrigerators need regular defrosting. There are four types of defrosting mechanisms: (1) Automatic, (2) Semi-Automatic, (3) Cyclical and (4) Frost-free. Semi-automatic refrigerators are defrosted by manually pushing a button to begin the defrost cycle. Once the button is pushed, the defrosting is done automatically. Automatic mechanisms defrost the fresh-food compartment automatically, but the freezer still has to be defrosted manually. In cyclical defrosting, the defrosting function is activated every 8 hours by a timer. The defrosting cycle lasts 20 minutes and the frost evaporates automatically. Frost-free refrigerators have an in-built thermostat, heater and a timer that activates the defrost cycle every 2 hours. The cooling coils are located outside the storage area. This feature ensures higher cooling efficiency. Some higher-end machines have sensor instead of a timer, which defrosts automatically and is the best defrosting system. The heater melts any accumulated ice and the water is drained away before the system starts to cool again.

Most new refrigerators are frost free as they save time and effort but they do tend to be more expensive.