Abstract: The multi-function energy management system has a plurality of predetermined operating programs stored in memory in or around a micro controller. The micro controller may be pre-set to operate a plurality of heating ventilation, air conditioning and other operating devices according to selected ones of such operating programs for maintaining the temperature in a room of a building at a desired ambient temperature condition and other loads at various operating conditions. The system has a continuously operating internal clock with a back up battery having a life span of ten years. Adjustment allowance is provided in the clock for leap years and daylight savings time. The system is capable of selectively operating the heating, ventilation, air conditioning devices and other energy consuming devices such as lighting, thermal storage heaters according to the occupancy of the room to provide a maximum saving of energy consumption.