One of the biggest obstacle to improve the energy efficiency in buildings essentially is that information about facts influencing energy consumption has not been grasped fully. One of the objects of Annex53 (Research about analysis and evaluation methods for total energy consumption in buildings) is to establish the prediction methods and evaluation tools with high precision. Based on it, it is possible to evaluate the facts and energy conservation technique influencing the total energy consumption objectively. On the other hand, many building energy simulation programs such as HASP/ACSS, BLAST, DOE-2, TRANSYS, EnergyPlus and BEST have been developed. Because it is possible to use these programs to compare and verify the function and performance of building and HVAC system and to analyze the facts influencing environment and energy performance of HAVC system with the index such as energy consumption in detail, these programs are considered to be powerful tools to evaluate the total energy consumption in buildings. However, at the present time, about the analysis of facts influencing the total energy consumption in buildings, it is not clear what tools could be used and how to apply them. In this paper, EnergyPlus, a HVAC system energy consumption calculation program developed by the University of Illinosis, the University of California and the Lawrence Berkeley National Laboratory, is taken up to be considered. Because EnergyPlus could be used not only to evaluate HVAC system energy consumption and indoor thermal environment but also to link with other programs such as COMIS, WINDOW5, TRANSYS and SPARK, it is possible to be used in all the countries of the world with wide range and various usage in the future.