Abstract: This document describes an energy management system in which microprocessor based thermostats are used to control individual room temperatures in a multiple room building in accordance with the known occupancy status of the room. The occupancy status information, as well as other control parameters, are transmitted to the thermostats from a central computer program. The control of a heating and cooling appliances is performed by an algorithm running on the electronic thermostat, which performs this function in accordance with these downloaded parameters. The system, allows room occupants to control the temperature of an occupied room within preset limits, automatically limits energy usage in unoccupied rooms, and provides additional facilities for energy management and general building management.