The expansion of solar energy in high density cities highlights the crucial need for optimal capacity planning in building-integrated photovoltaic (BIPV) systems. However, uncertainties present significant challenges for robust planning in these systems. Addressing this challenge, this paper proposes a distributionally robust optimization (DRO) model employing scenario robust ambiguity sets for BIPV system expansion planning to handle uncertainties in both demand and solar irradiance. This model stands out for its comprehensive incorporation of factors including the dynamics of climate change, the properties of building geometry, the intricate non-linear correlation between solar generation potential and global horizontal irradiance and uncertainty handling. The model can be transformed into a tractable formulation using the linear decision rule approach. In evaluating the model’s performance in data uncertainty handling, the study compares it against three alternative approaches – deterministic optimization, stochastic programming, and robust optimization – in a case study for BIPV system expansion planning for a college in Singapore. The findings demonstrate the superiority of the proposed model: it achieves a 5%–12% reduction in grid reliance, saves electricity cost by 3%–10% and reduces carbon dioxide (CO2) emission by 3%–10% compared to the benchmark approaches. These results underscore the capability of the proposed model in effectively handling data uncertainties in demand and irradiance in the BIPV system expansion planning.@en