Devices and methods for identifying an electrical device, and its state, in a network of electrical devices are disclosed. An energy monitoring device is programmed to identify an electrical device coupled to a power supply, and a state of the electrical device, from a change in successive measurements of the power supply. Algorithms for determining a load signature for an electrical device and its state are disclosed. A stored table of load signatures for states is used to identify devices, and states. Energy monitoring information is collected and presented to the user on a display, a remote display, or is transmitted over a network to a remote device such as a personal computer, personal digital assistant, an iPhone, a cell phone, voice mail, email, or text message.