This article explores the meaning of solidarity in European Union (EU) law in the context of the energy sector and the ongoing energy crisis. Energy provides a powerful and topical sectoral example of the fundamental role and diverse functions of solidarity in EU law. In its OPAL ruling in 2021, the Court of Justice of the EU established that energy solidarity constitutes a legally binding principle of EU energy law that should inform EU institutions and the Member States in their energy decisions. This article adds to legal scholarship on solidarity in three ways. First, it further develops the understanding of the ambiguous solidarity concept in EU law through the lens of the energy sector. Secondly, it contributes to the emerging body of energy law scholarship that seeks to advance the discipline of energy law by focusing on its doctrine rather than on its substantive developments. Finally, it provides a timely and novel analysis of the EU's recent emergency responses to address the acute energy crisis from the point of view of solidarity.
