Promotion of solar energy as a new promising renewable energy source for Smart City projects in Thailand plays an important role in driving the economy, society and the environment. A novel conceptual framework with different solar radiation indexes was developed to investigate and evaluate the efficiency of photovoltaic (PV) energy production by comparing predicted and actual results for energy acquired from the reference project. The trend of potential energy production was predicted from solar radiation data as the basis for further calculations to evaluate PV system efficiency through a techno-economic analysis of project development. A mathematical model was developed to predict the obtained electrical energy by considering the suitable location-specific solar radiation indexes including direct normal radiation, All-Sky insolation incident on a horizontal surface, direct normal irradiation and global horizontal irradiance. The developed model was tested with three existing Smart City projects at various locations in Thailand. The All-Sky index was determined as the most suitable option to evaluate new PV development projects. Highest energy production from the PV projects occurred in March and April. Energy production efficiencies of the PV systems were estimated in the range of 3.97-4.32 kWh/kWp. The techno-economic analysis suggested that the PV project had an internal rate of return of 14.30-15.75% and payback period of 6.18-6.74 years. The proposed conceptual framework was a promising tool for decision-making regarding Smart City PV projects. (C) 2021 Elsevier Ltd. All rights reserved.