An operation planning method performed in a system including a power generation device, a first electric load which operates using power generated by the power generation device, and a second electric load which generates heat using power generated by the power generation device, the second electric load including a heat generation unit which generates heat using power generated by the power generation device, a heat storage unit which stores heat generated by the heat generation unit, a first radiator unit which radiates heat stored in the heat storage unit, and a second radiator unit which directly radiates heat generated by the heat generation unit, said operation planning method being performed to design an operation plan for the second electric load, and said operation planning method comprising: predicting, for individual unit time periods, an amount of power to be generated by the power generation device, a first amount of power to be consumed by the first electric load, and a second amount of power to be consumed by the heat generation unit to generate heat to be radiated by the second radiator unit; the operation planning method being characterized by 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 first amount of power to be consumed and the second 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, the first amount of power to be consumed by the first electric load, and the second amount of power to be consumed by the heat generation unit to generate heat to be radiated by the second radiator unit are predicted using history information stored in a storage unit, and the history information including, for individual unit time periods, the first amount of power consumed by the first electric load, the amount of power generated by the power generation device, and the second amount of power consumed by the heat generation unit. predicting, for individual unit time periods, an amount of power to be generated by the power generation device, a first amount of power to be consumed by the first electric load, and a second amount of power to be consumed by the heat generation unit to generate heat to be radiated by the second radiator unit; the operation planning method being characterized by 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 first amount of power to be consumed and the second 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, the first amount of power to be consumed by the first electric load, and the second amount of power to be consumed by the heat generation unit to generate heat to be radiated by the second radiator unit are predicted using history information stored in a storage unit, and the history information including, for individual unit time periods, the first amount of power consumed by the first electric load, the amount of power generated by the power generation device, and the second amount of power consumed by the heat generation unit.