Researchers have developed a low-cost methodology using UAV photogrammetry and GIS analysis to assess rooftop PV potential in informal settlements, demonstrated in two communities in Brazil with favorable solar capture conditions. The process involves flight planning, image processing, rooftop analysis, and module allocation using an open-access Python tool. Results showed that approximately 577 modules could be installed, providing 61% of the average monthly electricity demand for each household, validated against detailed simulations with consistent results. The article also discusses a decision-support tool for assessing rooftop PV potential in informal settlements, comparing simplified irradiance-based models with dynamic simulation approaches developed by researchers from the University of Jaén in Spain and the Federal University of Bahia in Brazil.