A power trading system that executes power trading via a power system network and a network, comprising: a power supplier configured to generate power derived from exhaustible energy and supply the generated power to the power system network; a plurality of Vehicle to Grid apparatuses, each of which is connected to a renewable energy power generation equipment configured to generate power derived from renewable energy, and supplies power generated by the renewable energy power generation equipment to the power system network, characterized in that each of the plurality of apparatuses includes: a power control unit to which a battery is connected, and configured to control charge/discharge of the battery to determine electric energy stored in the battery, by charging the battery with power supplied from the power supplier via the power system network or power supplied from the renewable energy power generation equipment, and supplying power discharged from the battery to the power system network; a management unit configured to manage electric energy stored in the battery by discrimination between electric energy derived from exhaustible energy and electric energy derived from renewable energy, by managing the power trading via the power control unit based on a distributed ledger; and a communication unit that enables communication with the network; the distributed ledger is shared between the plurality of apparatuses, and includes information of electric energy supplied from the renewable energy power generation equipment to the power system network for each of the plurality of apparatuses, wherein the management unit calculates, based on information concerning electric energy derived from exhaustible energy and electric energy derived from renewable energy which are discriminatively managed as electric energy stored in the battery, an amount of CO 2 emissions from consumed electric energy of the battery by assuming that electric energy derived from renewable energy is preferentially consumed over electric energy derived from exhaustible energy among electric energy stored in the battery. a power supplier configured to generate power derived from exhaustible energy and supply the generated power to the power system network; a plurality of Vehicle to Grid apparatuses, each of which is connected to a renewable energy power generation equipment configured to generate power derived from renewable energy, and supplies power generated by the renewable energy power generation equipment to the power system network, characterized in that each of the plurality of apparatuses includes: a power control unit to which a battery is connected, and configured to control charge/discharge of the battery to determine electric energy stored in the battery, by charging the battery with power supplied from the power supplier via the power system network or power supplied from the renewable energy power generation equipment, and supplying power discharged from the battery to the power system network; a management unit configured to manage electric energy stored in the battery by discrimination between electric energy derived from exhaustible energy and electric energy derived from renewable energy, by managing the power trading via the power control unit based on a distributed ledger; and a power control unit to which a battery is connected, and configured to control charge/discharge of the battery to determine electric energy stored in the battery, by charging the battery with power supplied from the power supplier via the power system network or power supplied from the renewable energy power generation equipment, and supplying power discharged from the battery to the power system network; a management unit configured to manage electric energy stored in the battery by discrimination between electric energy derived from exhaustible energy and electric energy derived from renewable energy, by managing the power trading via the power control unit based on a distributed ledger; and a communication unit that enables communication with the network; the distributed ledger is shared between the plurality of apparatuses, and includes information of electric energy supplied from the renewable energy power generation equipment to the power system network for each of the plurality of apparatuses, wherein the management unit calculates, based on information concerning electric energy derived from exhaustible energy and electric energy derived from renewable energy which are discriminatively managed as electric energy stored in the battery, an amount of CO 2 emissions from consumed electric energy of the battery by assuming that electric energy derived from renewable energy is preferentially consumed over electric energy derived from exhaustible energy among electric energy stored in the battery.