A reference capacity determiner determines a reference capacity of each power storage apparatus, under an assumption that power is not transmitted/received among the customer facilities. An actual capacity determiner determines an actual capacity of each power storage apparatus, under an assumption that power is transmitted/received among the customer facilities. A characteristic value determiner determines a first number of charging/discharging cycles, under an assumption that power is not transmitted/received among the customer facilities and each power storage apparatus has the reference capacity. A charging/discharging plan determiner determines a second number of charging/discharging cycles, under an assumption that power is transmitted/received among the customer facilities and each power storage apparatus has the actual capacity, and determine a charging/discharging plan of the power storage apparatuses so as to minimize an objective function indicating a degree of degradation from the first number of cycles to the second number of cycles.