System Components Solar power cells make up the building blocks of a solar energy system. Multiple cells are usually combined into a complete module that also includes a frame for the system, electrical interconnections and mounting hardware. Multiple modules are frequently assembled into a "panel" that is then secured to the roof. Although solar energy (photovoltaic) modules are the most conspicuous and expensive component, a complete system also includes: an inverter to transform the DC output from the cells into usable AC current, wiring to connect the components module racks so that the modules can be securely mounted to a roof or on the ground at the appropriate angle. Solar power cells, as well as these "Balance of System" components are described in more detail in the referenced sections on the left.