Described are systems, methods, and apparatus that monitor potential voltage and/or radiated electromagnetic energy at a premises to determine device usage at the premises. The monitored potential voltage and/or radiated electromagnetic energy may be processed to generate voltage signature data and radiated electromagnetic energy signature data, a signature data pair, of an operational device and that signature data pair may be used to identify at least one of a device type, a device, a device element of the device, and/or an operational state of a device.