This paper describes the development of an estimation method of rational chiller maximum capacity. This technique, in conjunction with Taiwan’s TMY2 weather file, is used to develop the standard annual chiller energy consumption via DOE-2. Since 1995, central air-conditioned buildings have been regulated by the conventional “building envelope energy conservation design,” and it has proved to effectively prevent the HVAC system from vast energy use in Taiwan. Because many architectural personnel do not have the capability of executing the DOE-2 simulation, it is necessary to develop a simplified method that makes the cooling load calculation process less complicated and also similarly provides a basic way of estimating its annual energy usage. This enables architects to easily review building envelope design with respect to HVAC energy use from the initial design phase.Units: SI