Building rooftops, rich in sunlight and with high wind speeds, are among the most ideal locations for installing renewable energy systems (RES) in urban areas. However, not all rooftops are suitable for RES installation. Therefore, this study aimed to maximize energy harvesting using limited rooftop space. To this end, four scenarios were established based on a district in Seoul, South Korea, and the annual electricity generation of the RES was then estimated. This process was refined further into seven scenarios to assess economic feasibility. The principal findings of this research are as follows. First, depending on the type of RES installed on rooftops, it is possible to generate between 755,124 kWh and 3,236,918.3 kWh of electricity annually. Second, in terms of economic feasibility, scenarios predominantly featuring photovoltaic (PV) installations proved economically viable, whereas those mainly involving vertical axis wind turbines (VAWTs) did not guarantee economic feasibility. Third, for VAWTs scenarios with lower economic viability, adjusting the Renewable Energy Certificate weight and providing government subsidies up to USD1,131/kW could improve the profitability. These results provide a foundation for RES operators to design appropriate projects based on economic evaluations, and for policymakers to formulate effective policies to better promote the diffusion of RES.