How is a clean energy transition away from fossil fuels to be achieved? This paper tracks this burning question back to the 1970s and 1980s when nuclear energy was in the center of attention. Following a holistic case study approach, the nuclear project of the major Swiss electricity company BKW is investigated. Why had nuclear electricity turned from BKW's most promising field of business into its main business problem? This paper argues that the company's nuclear project was based on two wrong expectations: continuous growth of electricity consumption and decreasing average costs of production. In addition, three more general conclusions are drawn: 1) technical insights alone do not overcome fossil dependency, 2) capitalist logic poses the key obstacle to a clean energy transition, and 3) saving the planet requires a globally planned, democratically owned economy.