POWER DEMAND-SUPPLY SYSTEM

An electricity supply and purchase system (100, 100a to 100e) according to the present invention for transmitting electricity via an electric line (14) from an electricity transmission sender to an electricity transmission receiver, includes electricity transmission deciding means (40) for deciding an electricity transmission content including an electricity amount of the electricity transmission to be transmitted from the electricity transmission sender; electricity reception deciding means (43) for deciding an electricity reception content including an electricity amount of electricity reception at the electricity transmission receiver; a communication system (12) for communication between the electricity transmission sender and the electricity transmission receiver, the communication being carried out for matching consistency between the electricity transmission content and the electricity reception content; electricity transmission flow control means (41) for performing the electricity transmission from the electricity transmission sender to the electricity line based on the electricity transmission content for which the consistency is confirmed by the communication performed via the communication system; electricity reception flow control means (44) for performing the electricity reception at the electricity transmission receiver from the electricity line based on the electricity reception content for which the consistency is confirmed by the communication performed via the communication system.