Energy has been a core focus for CSTEP since its inception. One of our landmark initiatives was participation in the SERIIUS, a joint research consortium launched by former US President Barack Obama and Indian Prime Minister Manmohan Singh in 2009. One of the most impactful outcomes of this initiative is the RTSE tool, a transformative platform that helps users accurately estimate the solar potential of their rooftops and evaluate financial feasibility. RTSE aligns with India’s vision to achieve 500 GW of renewable energy by 2030 and net-zero emissions by 2070, directly contributing to the decarbonisation of the energy sector. Currently, the tool covers 120 cities across 25 states and four union territories under the Government of India’s flagship programme, PM Surya Ghar: Muft Bijli Yojana. The tool’s journey began in 2019 with the launch of CREST in Bengaluru. Using Light Detection and Ranging (LiDAR) technology, CREST created detailed rooftop maps, allowing BESCOM to identify and scale up solar adoption in the city. By 2024, the tool had evolved into the innovative RTSE tool that could offer accurate information regarding solar generation potential, optimal system design, and economics for each consumer and provide a list of all buildings suitable for rooftop solar panels with geographical coordinates and system sizes to the DISCOMs. This was done with the help of drone and satellite images. RTSE has been implemented in cities in Madhya Pradesh (including Bhopal, Jabalpur, Indore, and Gwalior) and Chhattisgarh (including Raipur, Durg, Bilaspur, Korba, and Raigad), enabling effective rooftop solar rollout in collaboration with state DISCOMs. Meanwhile, MNRE’s push for solar energy gave a fillip to the tool to assist the nation in the uptake of solar energy, with the Government’s official portal for PM Surya Ghar: Muft Bijli Yojana integrating RTSE. Between July and December 2024, over 100,000 users utilised RTSE to assess their rooftop solar potential and project financial savings over 25 years.