A PV system includes modules and a variety of structural and electronic components, known as balance of system (BOS) equipment, to tie the system together. Structural BOS equipment includes brackets, on which the modules are mounted. For ground-mounted systems, these brackets can be either fixed or able to rotate during the day to face the sun. Mounting systems that can rotate are known as tracking systems. Modules mounted on tracking systems tend to generate more electricity than modules on fixed-mount systems, all else being equal, because the tracking systems can optimize the amount of sunlight hitting the module over the course of a day.
One key piece of BOS equipment is an inverter, an electronic device that converts the electricity generated by PV modules into a form that is usable in the electricity system. Other electronic BOS equipment includes charge controllers, circuit breakers, meters, and switch gear. Some PV systems also include integrated energy storage systems such as batteries.