Stabilization of atmospheric concentrations of greenhouse gases to safe levels will require, at least in the longer term, some kind of technological revolution. This, in turn, can only be achieved through investments in the research, development and demonstration (RD&D) of carbon-free energy technologies. Innovation under Uncertainty presents original research and insights on the uncertain future of carbon-free energy technologies. The authors, by means of structured interviews with technology experts, portray a probabilistic landscape of future technologies' costs, potentials and limits to diffusion. This book collates the results of interviews with more than a hundred and twenty energy technology experts on a wide range of topics, from the impact of public European RD&D investment on the future cost of different low-carbon energy technologies to issues such as technological and diffusion barriers. The results offer important and concrete insights and recommendations concerning the potential role for public expenditure in innovation to bring clean generation technologies to the market. This unprecedented collection of qualitative and quantitative estimates will be invaluable to academics and policy makers drafting future energy policies, and integrated assessment and energy modelers characterizing the future development of different technological options.