The DOE-2 computer program has been used extensively in recent years for modeling energy conservation measures (ECMs). Due to the complex and time-consuming data gathering process demanded by the program, use of the model is most appropriate for complicated buildings. Methods that ran streamline the input: and output effort are possible. Retrofit measures simulated on a DOE-2 computer model, as opposed to manual methods, are simply executed and produce more reliable results. In addition, a completed computer model can be a powerful resource for an energy manager if used periodically to understand and control building energy use.