Gas Directive 2003 stipulates that all consumers must be free to choose their gas supplier by July 2007. The liberalisation of the gas market contributes to the establishment of a competitive internal market. In general, the liberalisation process is aimed at increasing welfare, in particular consumer welfare. Most of the literature relating to the liberalisation of the gas market is, however, primarily concerned either with the general economic notions of liberalisation and welfare, or with the specific legal aspects of the Gas Directive 2003. This paper takes an interdisciplinary and novel approach both the legal and economic ramifications of the Gas Directive 2003 are examined. More specifically, this paper reviews the main legal obligations emanating from the Gas Directive 2003 and examines their effect on consumer welfare in three Member States Belgium, Germany and the Netherlands. Full liberalisation was achieved in the three Member States by July 2004, but the positive effects of liberalisation are predominantly evident in Belgium and the Netherlands. The current structure of the German gas market seems to impede competition.