Photovoltaic system energy storage adds power generation to solar by incorporating battery technology to store any excess electricity for later use. Lithium-ion batteries are common because they have a high energy density, have a long cycle life, and have fast-charging abilities. A battery management system (BMS) oversees the charging and discharging processes and the health of a cell to ensure optimal performance. PV energy storage allows time-of-use shifting, enabling users to benefit from stored energy during expensive hours, or when solar generation is low. It also improves outage backup power, making photovoltaic systems more reliable and flexible.