It can take between two and 24 hours to naturally defrost a fridge freezer, depending on the room temperature and the thickness of the ice inside the appliance. You should make sure to dry the interior of your fridge freezer once it has been fully defrosted before switching the appliance back on though. This will prevent frost from quickly building up. Take note too that it can then take two to 12 hours for your fridge freezer to reach an optimal operating temperature once switched back on, so avoid filling it with fresh food straight away.