A hybrid approach, combining analytical sizing equations with long-term performance, for an optimal design of a stand-alone photovoltaic (PV)-battery system is proposed in this paper. This study explicitly examines the interaction of hourly variation of the load on the energy supplied from a stand-alone PV-generating source keeping the system 100% reliable, and a modification is proposed in the sizing algorithm to include the effect of loading profile. The correctness of the methodology is validated using an experiment exercise and by comparing it with other existing models. An adaptive feedback iteration technique, for fast convergence, is presented to obtain the best optimum combination for PV-battery configuration. A parametric analysis is carried out to examine the effect of load duration and charge controller low-voltage disconnect (LVD) on system sizing. A significant reduction of system requirements, i.e., up to 14%, is observed when the load is operating between 6 a.m. and 12 p.m. For a given condition, the optimum LVD of the charge controller is reported to be 11.4 V. The results of this study will serve any PV design engineer to decide the optimum system requirements and charge controller settings without compromising system reliability.