The transformation of energy systems is influencing economic policy agendas all over the world, particularly in industrialized countries. In this process, Germany has taken a pioneering role, and hence the technical innovations, legal frameworks, and business models established there are also of interest for other countries trying to achieve broader use of renewable energies. Energy cooperatives have been an important building block in the energy transition in Germany, although their practical importance is neither quantitatively nor qualitatively reflected in the academic literature. Drawing on recently collected data, this paper presents an overview of German energy cooperatives in terms of organization, financing, and membership. We then review literature from economics and the social sciences that has been used to analyze cooperatives on various levels in other fields. We discuss how these theories could be applied to create a better understanding of energy cooperatives, and we derive a preliminary research agenda for their analysis. We also assess the scope for interdisciplinary work among economists, sociologists, and other disciplines.