This recommended practice provides a procedure to size a stand-alone photovoltaic system. Systems considered in this document consist of PV as the only power source and a battery for energy storage. These systems also commonly employ controls to protect the battery from being over- or undercharged, and may employ a power conversion subsystem (inverter or converter). The issues of array utilization, battery-charge efficiency, and system losses are also considered in terms of their effect on system sizing. This recommended practice is applicable to all stand-alone PV systems where PV is the only charging source. This document does not include PV hybrid systems nor grid-connected systems. The hybrid systems referred to in the preceding sentence are off-grid but have multiple energy sources such as diesel generator, solar PV, and wind. This document is intended to be used in conjunction with IEEE Std 1013-2019 Recommended Practice for Sizing Lead-Acid Batteries for Stand-Alone Photovoltaic (PV) Systems. This recommended practice does not include the sizing of the system controller, inverter, wiring, or other system components.