Abstract: A settings data storage stores unique serial numbers and information regarding a plurality of patterns for alternately switching between normal operation for operating at high capacity and suppressed operation for operating at low capacity each unit time. A pattern specifier determines information for a pattern set in accordance with even and odd serial numbers. A water-heating heat amount determiner determines a heat amount necessary for water heating. A water heating scheduler establishes a water heating plan based on information regarding the pattern determined by the pattern determiner and the water-heating heat amount as determined by the water-heating heat amount determiner. A water heating controller alternately switches between normal operating and suppressed operation to heat water in accordance with the water heating plan established by the water heating scheduler.

Abstract: A settings data storage stores unique serial numbers and information regarding a plurality of patterns for alternately switching between normal operation for operating at high capacity and suppressed operation for operating at low capacity each unit time. A pattern specifier determines information for a pattern set in accordance with even and odd serial numbers. A water-heating heat amount determiner determines a heat amount necessary for water heating. A water heating scheduler establishes a water heating plan based on information regarding the pattern determined by the pattern determiner and the water-heating heat amount as determined by the water-heating heat amount determiner. A water heating controller alternately switches between normal operating and suppressed operation to heat water in accordance with the water heating plan established by the water heating scheduler.

Abstract: A water heater control system includes: a photovoltaic power generator interconnected with a commercial power supply, an electrical load circuit including a storage-type electric water heater using power from the commercial power supply and generated power of the photovoltaic power generator to perform a water heating operation of heating low temperature water to high temperature water and storing the high temperature water, and a HEMS controller limiting a water heating operation of the storage-type electric water heater by stopping or suppressing the water heating operation of the storage-type electric water heater when a power fee data for purchased power supplied to the electrical load circuit from the commercial power supply exceeds a standard monetary amount.