This book provides a thorough overview of the concept of whole energy systems and the role of vector-coupling technologies (VCTs) in meeting long-term decarbonization strategies. It is the first comprehensive reference that provides basic definitions and fundamental, applicable approaches to whole energy systems analysis and vector-coupling technologies in a multidisciplinary way. Whole Energy Systems presents practical methods with evidence from applications to real-world and simulated coupled energy systems. Sample analytical examples are provided to aid in the understanding of the presented methods. The book will provide researchers and industry stakeholders focused on whole energy systems, as well researchers and developers from different branches of engineering, energy, economics, and operation research, with state-of-the-art coverage and the latest developments in the field.