Why is renewable energy pursued so much more enthusiastically by some countries than others? The answer could simply be that countries with unresolved energy problems and an abundance of renewable resources pursue more ambitious policies. The author, however, argues that this is not so. Rather, renewable energy represents a potential future energy transformation and a major challenge to the existing energy system. It rises in the face of some of the most powerful energy actors the world has seen ? fossil fuels, nuclear and electric utility companies ? all of which have a vested interest in preserving the system. Moe analyzes the political economy of renewable energy in six very different countries (Japan, China, Germany, USA, Denmark and Norway) and energy structures, claiming that it is the extent to which states have successfully controlled these vested interests and prevented them from unduly influencing energy institutions that determines whether or not renewable energy has been a success.