As the Cop21 summit in Paris comes closer, various experts and organizations suggest ways to commit the financial sector and private investors to the energy shift and the ecological transition. But investment is not an end itself, and sustainability is measured on the demand side, not the supply side. One crucial problem to address in this respect is how to limit the rebound effects: financing a “sustainable” investment often results in creation of financial wealth that is not necessarily sustainable itself. “Special-purpose money” might offer an answer.