In this chapter, an overview of the various components of photovoltaic (PV) systems is provided. In particular, basic types and operations of PV modules, batteries, inverters, and controllers are described. In addition, typical stand-alone and grid-connected PV system configurations suitable for buildings are discussed. Finally, the design approach of various components of PV systems is outlined. Several calculation examples are presented to illustrate the design guidelines for PV systems integrated as part of the electrical power distribution for buildings.