One of the most popular techniques of renewable energy generation is the installation of photovoltaic (PV) systems using sunlight to generate electrical power. There are many factors that affecting the operation and efficiency of the PV based electricity generation systems, such as PV cell technology, ambient conditions and selection of required equipment. There is no much study that presents all factors affecting efficiency and operation of the entire PV system, in the literature. This paper provides a detailed review of these factors and also includes suggestions for the design of more efficient systems. The presented detailed overview will be useful to people working on theory, design and/or application of photovoltaic based electricity generation systems.