| 摘要 |
<p>PROBLEM TO BE SOLVED: To economize energy by a method wherein a retaining temperature in a time zone wherein the usage of hot water in an electric water heater of a hot water storage type is small is set low. SOLUTION: Water temperature is detected by a thermister 4 for each time zone obtained by dividing a unit period into prescribed terms of time, while the amount of usage of hot water is detected by a control part 6 from the variable in the water temperature, and the amount of usage of hot water in each time zone is stored for a plurality of unit periods. Based on the data stored in this way, the unit period is divided into the time zone wherein the amount of usage of hot water is large and those wherein the amount is small, and a heater 3 is controlled so that a retaining temperature in the time zone for which the amount of usage of hot water is determined as small be lower than the one in the time zone for which this amount is large. The unit period is set in one day and a period for storage of the amount of usage of hot water in one week. In another way, the unit period is set in one week and the period for storage of the amount of usage of hot water in a plurality of weeks.</p> |
