Chapter 1 presents the analytical framework used throughout the book to study how renewable energy policies in the EU member states emerged and have changed throughout the past three decades. In order to study renewable energy policymaking in the European Union (EU) and its member states and to untangle the complex policy processes that surround it, the authors draw on the Europeanization framework as their principal analytical tool. Adopting a Europeanization perspective allows emphasis to be put not only on the domestic drivers of national policy change, but also on the (sometimes neglected) role of the EU in renewable energy sources promotion. It also directs the analytical focus to the interactive nature of EU policymaking, characterized by an interdependent mix of uploading, downloading and cross-loading of policies and programmes between the European and the national levels and across EU member states. In order to adequately account for the multiplicity of factors that drive policy change in the European multi-level polity, the authors distinguish between three types of Europeanization – bottom-up, top-down, and horizontal – all of which prove to be relevant in some countries or at some point in time. By explicitly adding a horizontal dimension, the analytical framework goes beyond traditional concepts of Europeanization as a two-way process where member state governments either shape European policy outcomes (bottom-up Europeanization) or adapt to them (top-down Europeanization). Keywords: bottom-up Europeanization, Europeanization, horizontal Europeanization, policy diffusion, renewable energy policy, top-down Europeanization