Power is one of the key factors in boosting economies and living conditions in East African Countries. Kenya relies heavily on fossil fuels which consist of high electricity prices and pollution. In this study, we suggested a standalone method for typical residential energy consumption. We contrasted the use of a standalone photovoltaic (PV) system with a conventional grid connection. It shows the economic benefit of using power produced by PV, which lowers the cost of energy from the grid and allows them to eventually realize savings from the system. Therefore, this paper determines the ideal size of a rooftop solar home system that will satisfy all requirements for powering electrical appliances at a reasonable cost. Using the Hybrid Optimization of Multiple Energy Renewables (HOMER) software, a cost-based comparison of the two energy systems has been conducted. Apart from the HOMER simulation a manual easy to calculate approach is also provided that will help to size standalone systems in the absence of premium software.