The ‘Energy Union' can be seen as the most significant policy idea that seeks to reform European energy governance, policy and regional cooperation. However, so far the concept is mostly an empty box in which every stakeholder tries to put whatever is on the top of their priority list. This article reviews three major theoretical approaches to the analysis of European integration and EU policy that can be used to study the ongoing process of Energy Union formation. It then tries to structure the discussion by showing the evolution of the Energy Union concept, focusing on proposals by D. Tusk, J-C. Juncker and the European Commission, followed by a comparative analysis of four country cases representing different energy mixes and energy policy directions: Germany, France, Poland and Norway. All of these proposals are described and assessed according to their emphasis on the three dimensions of energy policy: security, affordability and sustainability. We sketch two possible scenarios for the future of EU energy policy, as suggested by the intergovernmentalist and supranationalist approaches and emphasize the potential impact of the governance mechanism of the Energy Union, which could reach far beyond what is expected and provide welcome coherence in Europe's energy and climate policy.
Policy relevance The article structures the policy debate on the Energy Union, discussing the different elements and instruments proposed by key EU actors and provides a useful overview of national interests of some important players, set in the context of their wider systemic conditions and policy goals. The framework for comparing the different proposals and national positions is built around the ‘energy policy triangle'. The article concludes with a discussion of possible future scenarios, as well as an in-depth discussion of the potential role of the governance mechanism.