Quantification of residential water-related energy needs cohesion, validation and global representation to unlock efficiency gains

Reduced energy consumption is essential for a rapid transition to net zero carbon emissions. Residential energy may constitute 27 % of primary energy consumption, and 20 %–50 % of residential energy is water-related energy (WRE). However, residential WRE consumption is difficult to quantify due to challenges in collecting data. The aim of this literature review is to critically appraise and compare models of residential WRE. This is the first literature review to provide a comparison of modelled estimates of residential WRE consumption. Reported values for residential WRE consumption were highly variable, ranging from 1 to 7 kWh/person/day. The results are not representative of the global population because 50 % of studies were conducted in Europe, while remaining studies were scattered across eight countries. 30 % of studies quantified energy consumption of specific end-uses (e.g. shower), and 40 % of studies only considered average consumption. Of the 61 studies reviewed, only four studies demonstrated clear validation of WRE consumption, and no studies validated energy consumption of individual end-uses. Therefore, it is difficult to determine whether the variability in reported results is due to true variability in residential WRE consumption, or uncertainty in the modelling approaches. Since successful water and energy reduction has been based on knowledge of specific end-uses, WRE models need better consideration of end-uses in order to inform design of interventions to reduce WRE consumption. Future research in this area also requires a greater focus on validation of modelling tools and wider geographical scope.