To provide a household electricity storing device which supplies its AC output to loads in the house by superposing the output upon commercial power supply in a time zone other than the midnight power supplying time zone by controlling the output current of the storing device to a value smaller than the total current consumption in the house measured by means of a current consumption measuring means.

When the electric current supplied from commercial power supply 17 is larger than a preset allowable value, an output opening/closing means 14 is closed by means of a signal from an overall control section 10. Then the output current of a household electricity storing device 1 is controlled to a value smaller than the total load current of the house and electric power is supplied from the storing device 1 to all loads used in the house by connecting the device 1 to the system of the commercial power supply 17. Therefore, the output of the device 1 will not flow reversely outside of the house and the stored inexpensive midnight power can be utilized effectively in the house during daytime. In addition, the output rating of the device 1 can be reduced, because the device 1 supplies part of the electric current consumed in the house.