The energy transition is a crucial aspect nowadays; the development toward sustainable and decentralized energy systems also passes through renewable energy communities. This thesis explores the development and implementation of Renewable Energy Communities (RECs), emphasizing their environmental, economic, and social impact. The study provides a comprehensive evaluation of the legal and regulatory frameworks, particularly in the Italian context, and the role of energy democracy in fostering local participation in renewable energy projects. Focusing on the case study of the "Energie di Comunità ETS" Foundation, a recently born initiative that has the aim of creating new configurations of renewable and solidarity-based energy communities on the initiative of the Archdiocese of Turin.