Net-Zero Energy Assessment of Multistoried Residential Buildings Integrated with Onsite Solar Rooftop PV System: A Case Study

India aims to achieve net-zero emissions by 2070 and generate half its electricity from renewable sources by 2030. The energy demand in residential buildings, especially multistoried buildings in urban areas, coupled with the growing adoption of room-based air-conditioning systems, poses a big challenge. The objective of this paper is to investigate the possibility of achieving net-zero energy status for multistoried residential buildings by incorporating a rooftop solar system as a source of onsite generation. The study involved examining the energy consumption and performance of ten residential apartment buildings in Kolkata, India. It examined ten apartments, comparing conventional construction to more energy-efficient aerated autoclaved concrete (AAC) blocks and better cooling options using the whole-building energy simulation tool eQUEST. The results indicated a 34–37% reduction in energy consumption compared to the base case, attributable to enhanced efficiency measures. To explore net-zero potential, three solar scenarios were explored, generating 16.16% (scenario A), 26.96% (scenario B), and 49.25% (scenario C) of energy. The assessment for achieving net-zero energy confirms the necessity for increased integration of energy-efficient measures alongside a wider array of renewable energy sources.