The energy policy about energy performance of buildings, including minimum energy requirements and energy performance certificate (EPC), is applied to new and existing buildings, especially in the case of energy retrofit. Among existing buildings, heritage buildings area special case. Another problem is finding an evaluation and measurement tool for town energy consumption which is related to the age and the characteristics of existing buildings. This problem concerns both urban planning discipline and heritage buildings discipline. The introduction of EPC database in Emilia-Romagna legislation (a region located in the North-East of Italy) is an opportunity to perform studies and simulation, in addition to GIS networking elaboration. This paper deals with the case of Ferrara, an old town, in order to debate: - number and energy incidence of heritage buildings; - influence of typology factor for energy saving in heritage buildings; - use of GIS tools to refer EPC, energy class in order to suggest a zone energy indicator (ZEI) for measuring the city and the old town. (C) 2012 Elsevier B.V. All rights reserved.