In this chapter, thermal modelling of different hybrid photovoltaic thermal systems, namely, air collector, water heater, distillation system, greenhouse and solar dryers, are presented. Thermal models are developed based on basic energy balance equations. Design and construction of the each system is presented along with validation of experimental results. An analytical expression for characteristic equation for photovoltaic thermal (PV/T) system has been derived as a function of design and climatic parameters. Statistical analysis of the system is also presented for the validation of experimental and theoretical results. Thermal modelling along with results of various configurations, like, series and parallel, mixed mode, duct and without duct, active and passive system, position of integration of PV modules, of PV/T systems are also presented. The effect of using glass to glass and glass to tedlar type PV modules on output of the system is also discussed along with results. For better understanding of design of PV/T system, solved examples and problems are given.