Abstract: Device, system and method of controllable power relay. For example, a power relay device, to controllably relay an electric power signal to a first device based on a control signal from a second device, may include a power input to receive an input electric signal; a power output; a control-signal receiver to receive the control signal from the second device, while the power relay device is galvanically separated from the second device; and a control module to controllably output the electric signal via the power output based on the control signal. Other embodiments are described and claimed.