This chapter presents a methodology to assess street-level solar irradiation in high-density urban environments using Google Street View (GSV) images, validated against field measurements and Hong Kong Observatory (HKO) data. Three key factors—solar geometry, atmospheric conditions (e.g., cloudiness), and street canyon morphology (sky view factor, orientation)—are integrated to quantify spatiotemporal patterns. Verification shows strong agreement between GSV-derived estimates and observational data (correlation coefficients: 0.86–0.98), confirming the model’s accuracy in capturing diurnal and seasonal cycles. Results demonstrate significant seasonal variation: summer irradiation exceeds winter by a factor of 3–5, driven by solar zenith angle changes and cloud cover. Spatially, low-rise areas (sky view factor ≥0.7) receive 3× more irradiation than high-rise zones (sky view factor ≤0.3), with West-East-oriented streets experiencing prolonged solar exposure in summer. Diffuse radiation dominates in winter, while direct radiation contributes 70% of summer totals. The study highlights the role of urban geometry, showing that high aspect ratios (H/W ≥ 2) reduce solar access by 80% in winter. Spatial inhomogeneity analysis reveals <10% variation in regional solar radiation, justifying the use of centralized HKO data. Limitations include unmodeled reflections and tree transmissivity, warranting future refinements. These findings provide critical insights for urban energy management and microclimate mitigation.