A heating, ventilation, air conditioning, and refrigeration system includes one or more variable frequency drives (VFD) controlled by one or more VFD controllers, which are configured to provide three-phase power to one or more three-phase AC motors and single-phase power to one or more single-phase AC motors. The system also includes a power source controller configured to select from a plurality of power sources based on availability of one or more power sources and time so as to maximize the economic efficiency of operating the system.