| 摘要 |
PROBLEM TO BE SOLVED: To reduce noise caused by a boiling operation in a nighttime zone.SOLUTION: A water heater 1 includes one or a plurality of hot water storage tank units 2 and a plurality of heat pump units 3 respectively connected to the hot water storage tank units 2. The water heater 1 can limit a number of heat pump units 3 that simultaneously operate boiling in a nighttime zone with inexpensive electricity prices, less than the whole number of heat pump units 3. |
