Renewable Energy Cooperatives (RECs) in Germany have received considerable attention in recent years, their number having risen to nearly a thousand since 2004. This growth has resulted largely from Germany's feed-in tariff system. Recent changes in this policy, however, have made the previous REC business models mostly unprofitable, so RECs are looking for new business models. Our study aims at identifying those new models and characterizing the implementation barriers RECs face. To this end, we interviewed REC members and management and observed REC annual general meetings. We found three significant barriers: first, risk aversion on the part of both members and management; second, concerns about the environmental impacts or the ethics of certain models that, while legal, are not felt to align with the intentions of lawmakers; finally, the lack of competencies and time of the mostly unsalaried REC management. These barriers could put the future of RECs at risk, and so threaten the contributions RECs make to the German Energy Transition. Professionalization, partnerships and other strategies can help mitigate this risk. If RECs are to continue to play an important role in the energy transition, policy makers would be wise to consider measures to support their continued growth.