NOVELTY - The apparatus (11) has a managed appliance registering unit authenticating an electronic appliance connected to a power network. A control unit controls operation of a managed appliance and supplies power to the managed appliance. The managed appliance registering unit transmits a challenge message that is used when registering the electronic appliance. The managed appliance registering unit collectively verifies response messages that are sent from the electronic appliance in reply to the challenge message.    USE - Power management apparatus for use as an eco-management apparatus in a power management system for managing an electric appliance. Uses include but are not limited to a plug in hybrid electric vehicle (PHEV), home appliance e.g. refrigerator and washing machine, personal computer, mobile telephone, video appliance e.g. TV set and recorder, capacitor, rechargeable cell, photovoltaic apparatus, wind power generating apparatus, geothermal power generating apparatus, fuel cell, natural gas power generating apparatus, biomass power generating apparatus and power company.    ADVANTAGE - The managed appliance registering unit transmits the challenge message that is used when registering the electronic appliance, and collectively verifies response messages that are sent from the electronic appliances in reply to the challenge message, thus registering the electronic appliance to manage the power efficiently and securely. The apparatus allows an information analyzing unit to perform calculation of a power supply pattern, thus reducing power consumption. The apparatus utilizes a control compliant appliance to inform occurrence of abnormality to the apparatus.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for registering an electronic appliance.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a power management system.    Power management system (1)    Power information gathering apparatus (4)    Power trading system (7)    Power management apparatus (11)    Managed block (12)