This book proposes the development of solar water heating applications. The theme is topical since it is linked not only to its economic advantages, but above all to considerations relating to environmental protection. Indeed, the operation of water heating systems, industrial or domestic, by this solar energy, is characterised by the absence of polluting discharges (fumes containing CO2 and Nox), radioactive dangers and bulky waste (nuclear centre). Overall, this book deals with the description of solar energy sources (thermal and photovoltaic), the structures of innovative water heating systems by these energy sources, the thermal and electrical modelling of water heating and the estimation of the yields of the different proposed systems. The proposed knowledge makes it possible to discover the field of renewable energy and to have knowledge of the applications of innovative solar heating systems currently marketed or under development in research laboratories. Also, it allows young researchers, doctoral students, academics and engineers to innovate in the field of solar energy and to develop efficient and hybrid solar water heating systems (thermal and photovoltaic energies). The experimental results, numerical simulations and economic studies proposed will be used by design offices to size and propose the appropriate installations for industrial and domestic applications.