The solar balance of system (BOS) refers to the components of a photovoltaic (PV) system that are not directly related to the solar panels themselves, but rather support their functioning. These components include items such as inverters, mounting systems, wiring, safety equipment, and monitoring systems. The BOS typically accounts for around 60% of the total cost of a solar PV system, with the actual solar panels accounting for the remaining 40%.

In order for a PV system to function properly, the BOS components must be carefully selected, installed, and maintained. This includes ensuring that the inverter is able to efficiently convert DC power from the panels into usable AC power for the home or building, that the mounting system is sturdy and weather-resistant, and that the wiring and safety equipment meet all necessary codes and regulations. By optimizing the BOS components, solar installers and homeowners can help maximize the energy output and overall system efficiency of their solar PV system.