A simplified optimization process (SOP) for determining set points is proposed and evaluated using the monitoring data and model of an existing VAV system. Controller set points, such as supply air temperature, supply duct static pressure, and chilled water supply temperature, are determined by this proposed SOP in order to minimize energy use while respecting thermal comfort. Zone air temperatures are also considered in order to obtain further energy savings. The proposed SOP uses the simplified VAV system model and certain monitored variables available in the existing control system. The evaluation results on the existing VAV system obtained by the SOP are consistent with that reached through the detailed optimization process (DOP) proposed elsewhere. It is concluded that the SOP proposed here could be implemented to determine on-line controller set points without requiring detailed calculations, including the detailed VAV model and optimization program.