The HEMS of each consumer transmits the amount of surplus electricity that is expected by to be generated by a PV system, and/or the amount of electric power that is needed by a controllable load, in a predetermined time slot on a predetermined date, to a server apparatus. The server apparatus, based on the notified amount of surplus electricity and the amount of electric power that is needed by the controllable load, combines a first consumer and a second consumer so that the amount of electric power needed by the controllable load will be equal to or greater than the amount of surplus electricity. Then, under the control the HEMS of the second consumer, the surplus electricity that is generated by the first consumer is consumed by each controllable load.
