This paper represents the measurement of the heat/air-conditioning energy consumption in a large open area using electronic technologies. This work is scoping the measurement and analyses of the energy-saving possibility for large open areas such as critical care units in hospitals that use central heat/AC systems. Zonal control is performed by closing the heat/AC Vents in the unoccupied sections of the open areas during the day. The heat/AC ON time is measured using a monitor circuit, which senses outdoor and indoor temperatures, according to the preferred temperature of the user. Factors that promote open-area zonal heat control systems include personal preferences, the area's dimensions and shape, distribution of Vents, the location of windows and doors, and direct sun exposure. Over a three-and-a-half-month test period in summer and fall, measurement results proved that the zonal control system of the open area could decrease average heating energy from 25.5% with all Vents opened to 18.3% with half of the Vents opened, with a difference of 7.2%, which amounts to 28.2% energy saving. The savings for air-conditioning are 13.57%. The saving varies depending on the temperature of the weather. According to our analysis, the zonal control has a negligible effect on the loading of the machine and on the comfort of the customers. These work results confirm the proposed idea of saving heat/AC energy by controlling the delivery of air on a zone-by-zone basis even in large open areas.