Discloses is a method and a corresponding apparatus for monitoring operation of electrical household appliances (such as a freezer). The method includes checking the temperature inside the freezer on a periodical basis and comparing with a de-frosting temperature. A critical condition is detected and recorded when the temperature inside the freezer stays over the de-frosting temperature for a period longer than a threshold value. In this way, when a user returns home after several days of absence, he or she is informed whether the food has been de-frozen and then frozen again because of a outage in the power supply network.