Over the last 30 years, a large amount of research on Photovoltaic Thermal (PV/T) collectors has been carried out by various researchers. This chapter presented an overview of this research, both in terms of an historic overview of research projects and in the form of a thematic overview, addressing the different design issues for PV/T. A thorough review of photovoltaic and photovoltaic thermal systems is done on the basis of its performance based on electrical as well as thermal output. Photovoltaic systems are classified according to their use, i.e., electricity production and thermal applications along with the electricity production. The application of various photovoltaic systems with its results is discussed in detail. The testing procedure of PV/T air collector is also discussed along with results. Design and construction of the different systems along with system photographs are described. The performance analysis including all aspects, e.g., electrical, thermal, energy, and exergy efficiency are also discussed.