In this paper different methods for energy building certification are analyzed in order to examine their application to a residential building into a new multi-functional building complex in Italy. In accordance with Italian and European standards, the authors evaluated the most representative apartment of the residential complex in order to certify all the other lodgings. Currently in Italy there are no existing national guidelines to certify energy performance of buildings, so the case study was evaluated by three different methodologies developed in Italy: CLASS, developed from the Province of Milan and B.E.S.T. Department of the Milan Polytechnic with the technical contribution of ANIT (National Association for the Thermal and acoustic Isolation), the methodology adopted in its own building code by the City of Perugia based on the standard of ITACA Protocol, and finally the CEIP® method elaborated by the Department of Industrial Engineering of the Perugia University. In this way the authors could compare different results obtained by three different methods and evaluate the advantages and disadvantages in order to suggest a better procedure mixing the best of each one. The research is elaborated with the background of the Italian law Digs 192/05, that aligns Italy with the European Directive EPBD 2002/91/CE. However, the legislator has not yet issued the decrees which make it operative.