Energy Systems Engineering is a comprehensive guide for students, researchers and professionals navigating through the rapidly evolving energy landscape. This book bridges theory and practice, delivering clear explanations of the origin of energy system modeling approaches, deliverables, performance analysis, and real-world applications across conventional and renewable technologies. From linear models to data-driven optimization, this book equips readers with the tools required to design efficient, sustainable and economically viable energy solutions. Reviews, case studies, numerical examples and analytical frameworks help translate complex concepts into practical insights. The book also covers smart grids, hybrid systems, storage technologies and sustainability assessments, which reflect current industry trends and research directions. Whether for coursework, project development or professional reference, this book empowers readers to understand, evaluate and innovate within modern energy systems, supporting the global transition toward cleaner, smarter and more resilient energy infrastructure.