This book presents various methods for sustainability assessment of energy systems, under various different conditions and scenarios. It answers the questions of how to measure the sustainability of energy systems by adopting appropriate metrics and methods. This book provides readers with a comprehensive view of the frontiers of sustainability assessment methods for energy system analysis. It presents various methodologies, allowing readers to understand: the complete metrics for sustainability assessment; life cycle thinking for sustainability assessment of energy systems; and the advanced sustainability assessment methods for energy systems. This book is of interest to researchers, engineers, decision makers, and postgraduate students within the field of energy systems, sustainability, and decision analysis.