Abstract: Control sub-systems, modularized on both a hardware and software basis are configurable to supplement an existing cogeneration system package, controlling and/or monitoring only essential control points of such cogeneration system to select thermal or electrical load following modes, or on and off modes, and to optimize the operation of the cogeneration system handling only a few control points. Various inputs of the cogenerator system are sensed and used in generating diagnostic or performance evaluation routines. Personality modules adapt the sub-systems to a particular cogeneration package type, and permit tailoring for economic considerations, such as local rates and schedules, performance characteristics and operating constraints of the associated cogeneration package and the like.