The reliance of future energy demand on standalone PV system is based on its payback period and particular electrical grid parity prices. This highlights the importance for optimum and applicable methods for sizing these systems. Moreover, the designers are being more sensitive toward simple and reliable sizing models for standalone PV system. This paper proposes a review on important knowledge that needs to be taken into account while designing and implementing standalone PV systems. Such a knowledge includes configurations of standalone photovoltaic system, evaluation criteria for unit sizing, sizing methodologies. Moreover, this review provides highlights on challenges and limitations of standalone PV system size optimization techniques.