Lower-level information processing devices (20-1 to 20-n) obtain parameters used for estimating power consumption in accordance with the statuses of electric devices (30-1 to 30-n), estimate the power consumption of the electric devices (30-1 to 30-n) on the basis of the parameters, and transmits the estimated value of the estimated power consumption to an upper-level information processing device (10). The upper-level information processing device (10) determines an assignment of distribution of supply and demand on the basis of the power supply-demand capacity in a predetermined power network and the estimated value of the power consumption and transmits the determined assignments to the lower-level information processing devices (20-1 to 20-n). The lower-level information processing devices (20-1 to 20-n) controls the operations of the electric devices (30-1 to 30-n) on the basis of the assignment of distribution of supply and demand.