Investigating the characteristics of residential hot-water consumption: A worldwide review

Residential Hot-Water Consumption (HWC) is a key component of the water-energy nexus at the household scale, and its accurate characterization is crucial for developing effective and sustainable water and energy management strategies, as well as for reducing the environmental footprint of the built environment. However, current knowledge of residential HWC is constrained by data fragmentation and methodological heterogeneity, underscoring the need for a comprehensive, standardized database to support robust comparative analyses across different contexts. In response to this gap, the present study provides a systematic and comprehensive literature review of residential HWC, synthesizing evidence from 77 scientific and technical sources referring to 59 distinct HWC databases. The investigation includes a preliminary phase examining available studies, their objectives, and levels of data aggregation, followed by a multi-level analysis at both the household and end-use (i.e. domestic fixture category) scales. This approach aims to explore HWC values, hot-water use parameters, and consumption profiles across multiple time scales. By providing a systematic comparison of HWC characteristics, assembling a consolidated open-access database, and identifying the underexplored areas, this review supports the derivation of transferable values and provides guidance for future research.