To provide a heat and electricity cogeneration system equipped with a power storage device which can improve efficiency of the entire system and reduce installed capacity.

In a heat and electricity cogeneration system equipped with a power storage device, power is supplied by using power by a power generator, commercial power, and power stored in the power storage device at the same time in a time zone in which power consumption of power load is equal to or greater than specific output C1, and the commercial power is stored in the power storage device by the commercial power in a time zone in which the power consumption of the power load is equal to or less than specific output C2. The commercial power is stored in the power storage device in a night time zone by the heat and electricity cogeneration system. Therefore, the commercial power stored at a peak period can be used and a backup power amount at the peak period can be reduced.