An energy management system has an application storage, an application executing unit, a plurality of network interfaces, a policy setting unit configured to set whether each application should be permitted to access each of the network interfaces, a policy storage configured to store identification information for each application set by the policy setting unit, and access permit/inhibit information showing whether the application is permitted to access each of the network interfaces, an I/F management unit managing a correspondence relationship between a network address and each of the network interfaces, and to specify a network interface used by the application executed by the application executing unit, and an access controller configured to judge whether the application executed by the application executing unit is permitted to access the network interface to be used thereby, based on the access permit/inhibit information stored in the policy storage.