Abstract: The present invention provides an Energy Management System which can be configured to automatically switch peripheral appliances on or off by detecting master appliances being in standby state, even though these appliances are located far away from each other in a premise, or even in other premises. The system is also capable of detecting whether the included appliances are plugged or unplugged to facilitate simple and efficient management of appliance power consumption for the sake of energy saving. In one embodiment, it also provides a detachable, battery-powered wireless sub-system, supporting dual operation modes, to improve wireless coverage of the system.