What assists and what hinders sustainable energy use in being put into effect? Two case studies of sustainable energy concepts-the Zurich Solarstromborse, where electricity can be purchased that is produced by solar panels, and the Swiss CO2-law, a consensus oriented implementation of the Kyoto-protocol-were analysed in order to investigate this question. In both case studies the unfolding of the sustainable energy concepts is reconstructed as a process starting with an abstract idea moving to a concrete realisation. This process passes through a series of different social worlds and is, in turn, affected by them. These social worlds are e.g. those of the concerned scientists, the professional investors, energy suppliers or governmental agencies. The case studies reveal three neuralgic challenges that have to be met when a concept advances from idea to realisation through the social worlds: Firstly, the translation between social worlds changes the content of the idea. Secondly, the way each social world looks at things (socially) constructs best solutions to problems and hides others. Thirdly, the actual dynamics of the social world within which it is finally implemented must be adopted by the idea. In order to integrate these neuralgic points, scientists as well as other inventors have to retain responsibility for their sustainable energy ideas and are requested to follow them through the social worlds in order to critically survey and eventually influence their "content in flux".