Energy service companies (ESCOs) are important agents to promote energy efficiency improvements. Although the European Commission and the Member States of the European Union (EU) have supported a number of policy initiatives to foster the ESCO industry, a recent survey of ESCO businesses in Europe has indicated that major differences exist in the development of the ESCO business among the various countries. The survey “ESCOs in Europe” covers EU-25, the New Accession Countries (NACs), Switzerland and Norway. With a few notable exceptions, such as Germany, Austria, Hungary, and to certain extent France, the ESCO industry is still in its infancy stage and ESCOs are struggling to get off the ground. Major differences exist among Member States not only in the development of national ESCO industries, but also in terms of actual type of ESCO projects (sectors, sizes, etc.) and their implementation (contractual terms, financing, etc.). This difference could be explained by several factors, such as different levels of support offered to ESCOs by national and regional energy authorities, local market structures and rules, and variation in the definitions, roles and activities of ESCOs.