An operation planning method performed in a system including a power generation device (211, 911), a first electric load (206, 906) which operates using power generated by the power generation device (211, 911), and a second electric load which generates heat using power generated by the power generation device (211, 911), said operation planning method being performed to design an operation plan for the second electric load, and comprising: predicting, for individual unit time periods, an amount of power to be generated by the power generation device (211, 911), characterized in that the method comprises: predicting, for individual unit time period, an amount of power to be consumed by the first electric load (206, 906); and designing the operation plan for the second electric load to cause the second electric load to operate during an operation period which includes, among the time periods, a time period in which an amount of reverse power is the largest, the reverse power being calculated by subtracting the amount of power to be consumed from the amount of power to be generated, wherein the amount of power to be generated by the power generation device (211, 911), the amount of power to be consumed by the first electric load (206, 906), and the amount of heat generated by the second electric load are predicted using history information stored in a storage unit, and the history information including, for individual unit time periods, an amount of power consumed by the first electric load, an amount of power generated by the power generation device, an amount of heat generated by the second electric load. predicting, for individual unit time periods, an amount of power to be generated by the power generation device (211, 911), characterized in that the method comprises: predicting, for individual unit time period, an amount of power to be consumed by the first electric load (206, 906); and designing the operation plan for the second electric load to cause the second electric load to operate during an operation period which includes, among the time periods, a time period in which an amount of reverse power is the largest, the reverse power being calculated by subtracting the amount of power to be consumed from the amount of power to be generated, wherein the amount of power to be generated by the power generation device (211, 911), the amount of power to be consumed by the first electric load (206, 906), and the amount of heat generated by the second electric load are predicted using history information stored in a storage unit, and the history information including, for individual unit time periods, an amount of power consumed by the first electric load, an amount of power generated by the power generation device, an amount of heat generated by the second electric load. predicting, for individual unit time period, an amount of power to be consumed by the first electric load (206, 906); and designing the operation plan for the second electric load to cause the second electric load to operate during an operation period which includes, among the time periods, a time period in which an amount of reverse power is the largest, the reverse power being calculated by subtracting the amount of power to be consumed from the amount of power to be generated, wherein the amount of power to be generated by the power generation device (211, 911), the amount of power to be consumed by the first electric load (206, 906), and the amount of heat generated by the second electric load are predicted using history information stored in a storage unit, and the history information including, for individual unit time periods, an amount of power consumed by the first electric load, an amount of power generated by the power generation device, an amount of heat generated by the second electric load.