A power controller, power control method, and power control system that enable prompt operation depending on the situation after a power failure are provided. A power controller includes: a communication unit (121) configured to acquire sensor data relating to a load apparatus (18) or a dispersed power source (15, 16); a nonvolatile storage unit (25) and a volatile storage unit (125) each configured to store the sensor data; a control unit (124) configured to control the load apparatus (18) or the dispersed power source (15, 16) based on the sensor data; and a backup power source (123) that is charged with a power source, and supplies power during a power failure, wherein the control unit (124) is configured to, when starting the power controller after the power failure, store the sensor data in the volatile storage unit (125) while the backup power source (123) is being charged, and store the sensor data in the nonvolatile storage unit (25) after the backup power source (123) is completely charged.