PowerDOE, a new, PC-based building energy performance simulation tool, combines the full capabilities of DOE-2.IE with an easy-to-use, flexible WindowsTM graphical user interfáce (GUI). This interface implements a number of unique approaches to fácilitate. developing an accurate building description. PowerDOE organizes architectural and HVAC elements in a hierarchy that is intuitive and familiar to designers and analysts. PowerDOE provides an interactive connection between the data input phase and the simulation, allowing the user to perform certain calculations prior to running the entire simulation. PowerDOE is a collaborative effort between the U.S. Department of Energy's Lawrence Berkeley Laboratory (LBL) and the Electric Power Research Institute (EPRI).