The growth-oriented, fossil-based energy system of today is undergoing a transformation towards renewable energies. However, a mere switch in technologies, without a thorough examination of underlying socio-economic relations and power structures, risks perpetuating the same crises of inequality and ecological degradation of the previous system. It follows then that a transformation in the energy system is required which enhances both social and ecological sustainability. The present research weaves together transformations and post-growth literature and constructs a qualitative analytical framework against which an initiative’s post-growth transformative capacity can be tested. It then zooms back in to empirically test the framework on energy communities in Greece. Results show that Greek energy communities hold significant post-growth transformative capacity, in areas such as networking, actor empowerment and innovative learning, shared vision creation, alteration of resource flows and a reconfiguration of ownership and governance structures. The research concludes with some policy recommendations that could enhance the post-growth transformative capacity of Greek energy communities, such as the creation of a national federation of energy communities. The post-growth transformative capacity framework presented in this research could be used as a descriptive starting point, from which academics or practitioners can build on to explore post-growth futures and post-growth transformative capacity in other sectors (e.g., food or transportation) and contexts (e.g., Global South countries).