PURPOSE: To enable an easy correction to be attained when a hot water feeding temperature is displaced from a set temperature by a method wherein a supplied calorie is calculated in response to a water temperature and a flow rate sensed by a feeding water temperature sensing means and a feeding water flow rate sensing means and then a supplying calorie control means is controlled in such a way as this calorie is supplied to a water heater.

CONSTITUTION: When a set temperature is inputted from a set temperature inputting means C, a control part F may calculate a supplied calorie required for feeding hot water having a set temperature in response to a fed water temperature and a fed flow rate of water sensed by a water feeding temperature sensing means A and a feeding water flow rate sensing means B and supply the calculated calorie to a water heater by a supplied heat calorie control means E. In the event that the fed hot water temperature is displaced from the set temperature, a shift temperature is inputted in such a way as a displacement of hot water temperature is corrected from a shift temperature input means D, resulting in that within the control part F, the set temperature inputted from the set temperature inputting means C is shifted toward a correcting direction. As a result, it is possible to make a coincidence between the hot water feeding temperature range and the set temperature range. With such an arrangement, the hot water feeding temperature is easily corrected.