The overarching question of this dissertation is in what ways complementary currencies (CC) systems can contribute to environmental sustainability from an institutional and ecological economics perspective. More particularly, the research focuses on household energy consumption, as it is an important target for policy makers in the EU. The first three chapters focus on the emerging trend of using CC systems as top-down instruments for environmental sustainability. Our findings relate to developing a taxonomy of these systems, designing new top-down CC systems adapted to the context of energy savings in the household sector, exploring the influence of these new systems on the quality of motivation in the light of Self-Determination Theory and investigating the acceptability and effectiveness of these systems. In the fourth and last chapter of this dissertation, we approach our research question from a bottom-up angle and, using an inductive methodology, we explore how community currencies could act as an organising instrument capable of helping cohousing communities achieve their energy-efficiency potential. Finally, we conclude by highlighting our contributions regarding the structure and important features of these systems, how they can be used in an ecological economics paradigm, and how they can set rules for collective action in an institutional perspective. / Doctorat en Sciences économiques et de gestion / info:eu-repo/semantics/nonPublished