A method for operating a frost treatment system including a first heating mat, covering a first zone and an intermediate zone of a second zone, operating alternately at a first energy level adjusted to maintain a first positive temperature on the first zone and a negative temperature on at least a part of the intermediate zone and at a second energy level adjusted to generate a positive temperature on the intermediate zone, a second heating mat covering the second zone apart from the intermediate zone and ensuring the defrosting function for the zone. This solution makes it possible to reduce the energy consumption of the first heating mat by reducing the energy level at which it is powered for most of the time. Also, an outer wall of an aircraft is provided including at least one frost treatment system operating according to this method.