Abstract: The present invention provides a novel system for monitoring a predetermined operating condition of a heating apparatus, such as a cumulative total time period of combustion and a combustion frequency, and informing a user of a timing of maintenance. In a hot water heater (1) according to the invention, a controller (208) outputs a maintenance requirement signal to a display (210) and a maintenance alarm to inform the user of a timing of maintenance when a combustion frequency nx becomes equal to or greater than a first reference value nr1 or when a cumulative total time period of combustion tx becomes equal to or greater than a second reference value tr1. This allows the user to perform maintenance without delay and prevents troubles or abnormalities from being developed in the hot water heater (1).