ABSTRACT Hybrid renewable energy systems (HRES) must be leveraged to an extent that curtailment of fossil fuel does not hinder economic growth. However, owing to their intermittency, HRES must be supported with energy storage systems (ESS) that are quite expensive. Hence, optimal sizing of such systems is advisable to improve utilization and efficiency. In this paper, a comprehensive assessment and optimal sizing of HRES, consisting of floating and rooftop solar energy, wind energy systems, and battery-energy storage system (BESS) is presented and evaluated for a smart city, Visakhapatnam, India. Open-source tools such as web-based Bhuvan GIS, the polygon tool in Google Earth and Sketch Up are used identify the potential areas and for a realistic assessment of these renewable energy technologies. It is estimated that the proposed location has a potential of 105 MW of floating solar with 20% utilization of water bodies, 260 MW of rooftop bifacial PV system with an assumed acceptance rate of 5%. In addition, 62 MW of wind energy is estimated over shorelines and hilltops. With the upper limits of HRES, various multi-objective optimization techniques, differential evolution, mutation-based PSO, Quantum-behaved PSO, and mutation-based QPSO, are applied to minimize reliability indices like Levelized cost of energy (LCoE), loss of power supply probability (LPSP), and Life Cycle Emissions (LCE). Sensitivity analysis is performed to assess the impact of techno-economic changes, such as load appreciation, damage to batteries, and price changes. The results show that the proposed hybrid structure helps in combating carbon emissions with LPSP in acceptable limits of 0.285% to 0.3% while LCoE is in between 0.9 $/kW and 0.11 $/kW.