A power supply-and-demand control system comprising: a plurality of nodes (10-6, 10-7) incorporated in electrical apparatuses of a local power system, respectively, each electrical apparatus including at least one of a power generation apparatus and a load apparatus, either configured to be supplied with power from a commercially available power system; and a communication medium configured to achieve communication between the nodes (10-6, 10-7), wherein each of the nodes comprises: a communication path unit configured to establish a communication path for transmitting and receiving data to and from at least one adjacent node (10-6, 10-7) through the communication medium; a communication control unit configured to receive and transmit average supply-and-demand state data from and to the at least one adjacent node (10-6, 10-7) through the communication path established; and a controller configured to execute self-control programs to achieve self-control of each electrical apparatus, to adjust the power to generate or consume in the electrical apparatus incorporating the node (10-6, 10-7), in accordance with the average supply-and-demand state data, and to calculate an average supply-and-demand state value corrected based on a value by which the power has been adjusted; wherein the communication control unit is configured to transmit data representing the corrected average supply-and-demand state value calculated by the controller, to any other node connected to the node by the communication path, and thereby adjusting a supply-and-demand balance in the local power system comprising the electrical apparatuses. a plurality of nodes (10-6, 10-7) incorporated in electrical apparatuses of a local power system, respectively, each electrical apparatus including at least one of a power generation apparatus and a load apparatus, either configured to be supplied with power from a commercially available power system; and a communication medium configured to achieve communication between the nodes (10-6, 10-7), wherein each of the nodes comprises: a communication path unit configured to establish a communication path for transmitting and receiving data to and from at least one adjacent node (10-6, 10-7) through the communication medium; a communication control unit configured to receive and transmit average supply-and-demand state data from and to the at least one adjacent node (10-6, 10-7) through the communication path established; and a controller configured to execute self-control programs to achieve self-control of each electrical apparatus, to adjust the power to generate or consume in the electrical apparatus incorporating the node (10-6, 10-7), in accordance with the average supply-and-demand state data, and to calculate an average supply-and-demand state value corrected based on a value by which the power has been adjusted; wherein a communication path unit configured to establish a communication path for transmitting and receiving data to and from at least one adjacent node (10-6, 10-7) through the communication medium; a communication control unit configured to receive and transmit average supply-and-demand state data from and to the at least one adjacent node (10-6, 10-7) through the communication path established; and a controller configured to execute self-control programs to achieve self-control of each electrical apparatus, to adjust the power to generate or consume in the electrical apparatus incorporating the node (10-6, 10-7), in accordance with the average supply-and-demand state data, and to calculate an average supply-and-demand state value corrected based on a value by which the power has been adjusted; wherein the communication control unit is configured to transmit data representing the corrected average supply-and-demand state value calculated by the controller, to any other node connected to the node by the communication path, and thereby adjusting a supply-and-demand balance in the local power system comprising the electrical apparatuses.