The widespread adoption of rooftop photovoltaic solar panels in urban environments presents a promising renewable energy solution but may also have unintended consequences on urban temperatures. This is primarily due to their lower albedo, which leads to increased heat absorption and enhanced thermal convection between the panels and the underlying roof surfaces. Here we show that, in Kolkata, city-wide installation of these rooftop photovoltaic solar panels could raise daytime temperatures by up to 1.5 °C and potentially lower nighttime temperatures by up to 0.6 °C. Our study also reveals that rooftop photovoltaic solar panels significantly alter urban surface energy budgets, near-surface meteorological fields, urban boundary layer dynamics and sea breeze circulations. Comparative analysis with cities, such as Sydney, Austin, Athens and Brussels, supports these findings, providing valuable insights for policymakers on managing large-scale solar panel installations. Understanding these effects is crucial for balancing the benefits of renewable energy with its potential impacts on urban climates.