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 .