An electrical power infeed module for modular electrical power systems selectively provides power to one or more electrical outlets in the system from a single power source, regardless of the number of power sources are engaged by power infeed modules in the system. The power infeed module includes a power infeed cable, a power output cable, and an electrical circuit disposed between the power infeed cable and the power output cable, the electrical circuit being operable to selectively connect the power output cable to the power infeed cable if the power infeed cable is connected to a first power source and the power output cable is not already electrically energized by a second power source. The circuit includes an electrical switch, a sensor for detecting whether the power output cable is electrically energized, and a controller for operating the switch in response to a signal from the sensor.