An on-site power plant (24) has a controller (40) that selectively controls operation of prime movers (26, 28, 30). In one example, the controller (40) changes the number of operating prime movers responsive to a transient in a load (22) requirement while continuing to operate at least one of the prime movers. One example includes prioritizing the prime movers (26, 28, 30) for operation based upon the needs of a cogeneration unit (32, 34, 36) associated with the prime movers for providing a temperature control function within a facility. Another example includes controlling operation of the prime movers based upon a capacity for fueling the prime movers.