Household analysis identifies water-related energy efficiency opportunities

Water heating accounts for around one third of household direct energy use. This energy demand is some four times greater than lighting. Here we use detailed monitoring and modelling of seven individual households to quantify major factors. Using normalized sensitivity results we demonstrate (i) high variability and (ii) a large and consistent influence of shower duration, flow rate, frequency and temperature along with hot water system efficiency, adult population, and the temperature of cold water. A 10% change in these factors influenced 0.1–0.9 kWh/hh-person.d, equivalent to a 2–3% of total household energy use. We draw on 5399 shower events from a further 94 households, and 491 shower temperature measurements to understand the scope for changes to the households. Individual parameters variation guided by these larger datasets demonstrated shower duration and flow rate offer most scope for change. The work helps guide city-scale analysis of household water-related energy demand. It also supports the tailoring of behavioural and technological water-efficiency programs towards those with strongest potential to influence energy. Strong interaction between parameters suggests that programs aiming to influence water-related energy need to be aware of how this interplay either amplifies, or diminishes, the intended energy savings