Towards urban energy independence: Case study of residential hidden energy-water nexus

• This study uncovered overlooked energy sources within buildings. • Investigated energy potential of rainfall, potable water, and sewage biomass. • Potable water demonstrated the highest energy yield among sources. • Small-scale electricity generation can contribute to buildings and urban energy resilience. • The case study illustrated the feasibility of domestic water-energy nexus applications. The world faces an energy crisis due to increasing demand, fluctuating supply, and energy security challenges. This study proposes a novel integrative framework for small-scale hydropower systems harnessing locally available water resources and quantifying three often-overlooked energy sources from residential water systems: rainwater, potable water, and sewage biomass. Unlike previous studies that focus on a single source, our approach evaluates these sources simultaneously at the building scale, using a university dormitory complex, including 11 buildings, with 2,400 residents as a case study. We modeled energy yields under low, base, and high scenarios and translated outputs into tangible metrics − the number of smartphones, laptops, and e-bikes charged per year. Our analysis across various scenarios revealed that the system’s annual potential ranges from 6,553 to 11,941 kWh/year, sufficient to charge approximately 1,352–2,463 smartphones, 345–628 laptops, and 52–95 e-bikes annually. Potable water contributed the highest and most stable share of energy, up to 11,599 kWh/year, making it the most promising source for future investment. This research demonstrates the potential of small-scale renewable infrastructure in residential areas, showing that integrating overlooked water and energy sources can support self-sustaining buildings, reduce carbon footprints, and enhance energy resilience. By advancing the building-level energy-water nexus, our findings support the design of self-sustaining buildings and resilient urban communities.