Satellite-Based Assessment of Rooftop Rainwater Harvesting and Solar Energy Potential in Hamirpur City, Himachal Pradesh, India

India faces a growing water crisis driven by pollution, inadequate infrastructure and climate change, while rising energy demand continues to strain fossil fuel resources. Innovative technological interventions such as rooftop rainwater harvesting (RWH) and solar photovoltaic (PV) systems offer integrated solutions to address the challenges of the water crisis. The present study, conducted during 2023–2024, analyzed potential of harvesting rainwater as well as solar energy from the rooftops of 260 buildings with a total digitized rooftop area of 53,235 m² that comes under the Municipal Committee of Hamirpur city in Himachal Pradesh, India. The city has a humid subtropical climate with a mean annual rainfall of 1,298 mm, concentrated mainly during the southwest monsoon season. The city-wide annual RWH potential is estimated at 1,479,118.5 m³, which was found to meet satisfactorily 47.68% of the current municipal water demand of the city. In addition, the rooftop potential of harnessing solar PV energy is computed as 0.226 million kW, which is sufficient to meet about 66.29% of the city’s electricity demand, if fully utilized. Benefit-cost ratio (BCR) indicated attractive economics, with a BCR of 3.0 for RWH and 5.6 for solar PV based on prevailing electricity tariffs and system costs. The findings of this study are useful to plan efficient utilization of the harvested rainwater and solar energy with improved productivity sustainably. Moreover, the methodology adopted in this study may be easily replicated in other places to obtain probable amounts of rainwater and solar energy that can be successfully harvested and better utilized in adverse climate settings.