This paper is based on findings resulting from ASHRAE Research Project RP-1477.The paper summarizes the results of a series of analyses to assess the impact of the selection procedure used to generate of typical year weather on annual building energy use. The building energy analysis is carried out using detailed whole building simulation tool that utilizes hourly typical year weather files. Annual energy use for prototypical office buildings are obtained for 10 sites representing a wide range of climatic conditions in the U.S. In particular, the analyses presented in this paper evaluate the impacts of weighting factors for various weather variables and of the length of historical data used on predicting the energy use of building systems.The results of the analysis indicated that a maximum of 5% difference in annual office building energy use can result from the selection procedure used to generate typical weather year for the 10 US climates considered in this study.Units: Dual