Changes to energy behaviour -- the role of people and organisations in energy production, use and efficiency -- are critical to supporting a societal transition towards a low carbon and more sustainable future. However, which changes need to be made, by whom, and with what technologies are still very much under discussion. This book, developed by a diverse range of experts, presents an international and multi-faceted approach to the sociotechnical challenge of engaging people in energy systems and vice versa. By providing a multidisciplinary view of this field, it encourages critical thinking about core theories, quantitative and qualitative methodologies, and policy challenges. It concludes by addressing new areas where additional evidence is required for interventions and policy-making. It is designed to appeal to new entrants in the energy-efficiency and behaviour field, particularly those taking a quantitative approach to the topic. Concurrently, it recognizes ecological economist Herman Daly's insight: what really counts is often not countable.