To eliminate an occurrence of lack of hot water caused by poor accumulated heat during a solar heat accumulating operation.
There is provided a heat accumulating hot water storing tank 3 for use in storing hot water of which temperature is increased and its heat is stored during a solar heat accumulating operation. There is also provided an electrical heated hot water storing tank 2 for use in storing hot water boiled up by an electrical power heater 15. There is provided a hot water feeding means 38 for selectively performing an individual hot water feeding from one of the heat accumulative hot water storing tank 3 and the electrical heated hot water storing tank 2 and a mixed hot water feeding from both of them. The heat accumulative hot water storing tank 3 is provided with a heat accumulative electrical power heater 20. Mid-night electrical power is supplied to the electrical power heater 15 for the electrically heated hot water storing tank 2 to perform a high temperature boiling-up operation. Mid-night electrical power is supplied to the heat accumulative side electrical power heater 20 of the heat accumulative hot water storing tank 3 so as to perform a boiling-up operation. A temperature of hot water in the heat accumulative hot water storing tank 3 is increased by a predetermined temperature in correspondence with a lack of accumulated heat during the solar heat accumulating operation.
NIWAYAMA AKIRA
IRINO KENJI
