Renewable energy sources are starting providing a substantial part of the energy supplied to end-users in many countries of the world because of a series of environmental and economic benefits associated with their usage. This progressive shift towards renewable energies may entail a very scarcely investigated change concerning how time and space are perceived and used within social practices. By drawing on complex adaptive systems theory and social practice theory, the authors of this conceptual paper provide a series of insights on the nature of this change. They focus in particular on renewable energy sources being integrated into electricity networks and show how this change is essentially driven by the fact that renewable energy sources can constitute interconnected funds of energy distributed over a large spatial area and regenerated according to fluctuating rates. Then, they discuss how these aspects have an impact on the evolution of the complex energy systems at stake and which are their implications for energy related decision making. Based on these preliminary observations, they finally address the main subject of the paper and contend that the complexity and the ever increasing power capacity of these energy systems require that energy conservation policies will have to include a new generation of policies. In doing so, they show how these new policies have to increasingly address the temporal dimension of energy consumption and have to complement so-called “smart” ICT based energy management approaches with policy solutions relying on new social practices. In particular, they provide a series of arguments and practical examples illustrating why the sustainability of the complex energy systems under investigation can in principle be more effectively pursued by implementing energy conservation policies integrating technological solutions with governance rules envisaging an active and collective participation of local communities in the management of energy. ; JRC.F.7-Renewables and Energy Efficiency