An energy management system comprising an energy storage controller for performing control to store power generated by photovoltaic power generation facilities in energy storage facilities, comprising: a battery and an electric water heater as the energy storage facilities; and a control unit to control thermal storage of the electric water heater and charging of the battery as the energy storage controller; characterized by further comprising: an equipment specification data management unit to manage data on charging/discharging loss of the battery and other data on heat radiation loss of the electric water heater, wherein the control unit is configured to: - acquire data on the battery loss, and charging/discharging loss of the battery, and data on the heat radiation loss of the electric water heater from the equipment data management unit; - compare a value acquired by totalizing the battery loss and the charging/discharging loss of the battery with a value of the heat radiation loss of the electric water heater, and - give priority based on the comparison to the energy storage facility with lower loss and store energy therein. a battery and an electric water heater as the energy storage facilities; and a control unit to control thermal storage of the electric water heater and charging of the battery as the energy storage controller; characterized by further comprising: an equipment specification data management unit to manage data on charging/discharging loss of the battery and other data on heat radiation loss of the electric water heater, wherein the control unit is configured to: - acquire data on the battery loss, and charging/discharging loss of the battery, and data on the heat radiation loss of the electric water heater from the equipment data management unit; - compare a value acquired by totalizing the battery loss and the charging/discharging loss of the battery with a value of the heat radiation loss of the electric water heater, and - give priority based on the comparison to the energy storage facility with lower loss and store energy therein. an equipment specification data management unit to manage data on charging/discharging loss of the battery and other data on heat radiation loss of the electric water heater, wherein the control unit is configured to: - acquire data on the battery loss, and charging/discharging loss of the battery, and data on the heat radiation loss of the electric water heater from the equipment data management unit; - compare a value acquired by totalizing the battery loss and the charging/discharging loss of the battery with a value of the heat radiation loss of the electric water heater, and - give priority based on the comparison to the energy storage facility with lower loss and store energy therein. - acquire data on the battery loss, and charging/discharging loss of the battery, and data on the heat radiation loss of the electric water heater from the equipment data management unit; - compare a value acquired by totalizing the battery loss and the charging/discharging loss of the battery with a value of the heat radiation loss of the electric water heater, and - give priority based on the comparison to the energy storage facility with lower loss and store energy therein.