An externally-controllable electrical power generating system for providing auxiliary or backup power to a load bus or device. The system may be used indoors, and generally includes a power source comprising a first DC output, an electrical storage unit comprising a DC input coupled to the first DC output of the power source, the electrical storage unit further comprising a second DC output. An inverter coupled to the second DC output receives power, the inverter having a first AC output that can be synchronized with an AC load bus or AC grid. The system includes a contactor connected between the first AC output and an AC load bus, and is controllable with an external controller operated by a utility or a managing entity, such that the external controller can enable the controller to connect or disconnect the contactor.