An electric power control system of the present invention is connected to an electric power supplying means for supplying electric power and a load means for accepting supply of electric power and consuming the electric power. The electric power control system includes: a supplied energy acquiring means for acquiring a supplied energy, which is the amount of electric power supplied from the electric power supplying means; a consumed energy acquiring means for acquiring a consumed energy, which is the amount of electric power consumed by the load means; and an electric power supply and demand controlling means for, depending on a total supplied energy as the total of the acquired supplied energy and a total consumed energy as the total of the acquired consumed energy, transmitting and/or receiving electric power to and from another device to change the total supplied energy.