To achieve maximum safety, durability, cost-effectiveness and overall system performance, a stand-alone photovoltaic power system must be designed and installed following existing guidelines and codes. Numerous software tools exist to achieve this but many of them are for pre-feasibility analysis, simulation, optimization and research and development. They are rather too sophisticated for system designers and installers who need user-friendly and accurate tools to get the job done in the shortest possible time. This paper presents the development of a Matlab/Simulink-based sizing and simulation tool that utilizes the graphical powers of Simulink and offers the designer a user-friendly platform to size the system components using site-specific design parameters and perform cost estimate of any intended stand-alone photovoltaic power system. The robustness of the tool is validated by the agreement of the results with those of analytical methods.