A control device (200) calculates, on the basis of the transition of the expected amount of power generation of a power generation unit (160), the transition of the expected amount of power supply of a power supply unit (110), and the current amount of stored electrical power of a storage battery (120), a transition of the expected amount of the stored electrical power of the storage battery (120) in a case where electrical power continues to be supplied from a power distribution network (300) to the storage battery (120). In addition, the control device (200) sets a power reduction time zone, which is a time zone in which no electrical power is supplied from the power distribution network (300) to the storage battery (120), when the presence of a first time, which is a time when the expected amount of the stored electrical power starts to exceed the first reference capacity, is shown in the transition of the expected amount of the stored electrical power of the storage battery (120), and sets the end time of the power reduction time zone as the first time.