Recently the application of hybrid energy systems observed to be potential technologies at research and semi-commercialized level to come up with sustainable energy systems. Particularly Wind/Solar Hybrid Energy Systems have been seen to be reliable technologies as they are complementary; avoiding the challenges of power intermittent, high cost, unexpected energy shortages, and excess electricity production which are major problems when wind or solar power systems are employed alone. This book, therefore, provides an understanding in applying these systems for electrification especially for off-grid areas and also for other applications. These topics span a wide range, from Wind/Solar energy potential assessment, through optimization techniques to economics and environmental concerns. The book can be used by students, engineers, investors who want to know the application, the design, the analysis and sizing of Wind/Solar Hybrid Energy Systems. Moreover; this book will be useful for researchers in developing countries who work on rural electrification as very good reference.