This book addresses the question: how effective are countries in promoting the innovation needed to facilitate an energy transition? Chapters explore energy policy and institutions, innovation policy in general, as well as energy innovation in key countries, including the US, Germany, the UK, China, Japan and Korea, and the EU. At the heart of Energy Innovation for the 21st Century is a fascinating set of international empirical case studies covering supply and demand side technologies at different levels of maturity. These are set within an analytical framework encompassing the functions of technological innovation systems and innovation metrics. The book explores energy, science and technology policies, contextualising the case studies to aid the assessment of the overall performance of innovation systems. Drawing together lessons for energy innovation policy and institutional design, this book is a much-needed resource for sustainability and innovation scholars and researchers. Policy-makers and practitioners will also benefit from the practical advice offered in this timely volume.