1. A computerized method for selecting a mechanical power source for a shaft-driven device from two or more available mechanical power sources, the method comprising the steps of: providing the shaft-driven device connected to the two or more available mechanical power sources via one or more couplings and one or more drive shafts, wherein the two or more available mechanical power sources comprise at least one motor/generator coupled to an electrical network connection and at least one mechanical power source selected from the group consisting of one or more engines, one or more motors, and one or more turbines; providing a processor communicably coupled to a database and one or more interfaces to the two or more available mechanical power sources, the shaft-driven device and the one or more couplings; (a) receiving market and operational data related to the two or more available mechanical power sources, the shaft-driven device, the one or more couplings and the electrical network connection; (b) analyzing the market and operational data related to the two or more available mechanical power sources, the shaft-driven device by the processor, the one or more couplings and the electrical network connection; (c) selecting the mechanical power source for the shaft-driven device from the two or more available mechanical power sources based on a set of financial parameters by the processor, wherein the set of financial parameters comprises an estimated operational cost for the at least one motor/generator and the at least one mechanical source, and a projected potential revenue from using the at least one mechanical source to drive both the shaft-driven device and the at least one motor/generator to provide electricity to the external network connection; and (d) whenever the shaft-driven device is not already connected to the selected mechanical power source, the processor (1) determines whether it is profitable to switch the shaft-driven device to the selected mechanical power source based on the projected potential revenue and a projected cost associated with switching to the selected power source, a time period and one or more guidelines, and (2) physically switches the shaft-driven device to the selected mechanical power source by automatically sending one or more control signals to the one or more couplings whenever it is profitable to switch the shaft-driven device to the selected mechanical power source.