Household Hot Water Temperature - An Analysis at End-Use Level

“The supply of hot water to households via indoor plumbing fixtures has become the norm in regions with a relatively high level of service. Understanding household hot water temperature is important for various reasons, including the link to energy use, -water quality, and it is an important input parameter for end-use modelling. In some cases the water is heated in a geyser, also called a hot water cylinder; in other cases the end-use appliance may receive cold water yet have an internal heating element. Previous studies into hot water have focused on the wasted volume of water while waiting for hot water to arrive at the point of use and on energy saving, say by reducing the hot water supply temperature, or improved insulation. End-use modelling of household water use allows for segregation of hot water and cold water uses, with application to the water-energy nexus in relation to water conservation and -saving. End-use models require at least three different temperature parameters to segregate water use in this manner: the hot water supply temperature, cold water supply temperature and the desired (or blended) water temperature at point of use. This paper presents insight into these three temperature-parameters with a focus on the desired water temperature, with cognisance of various end-uses in a home. The results are based on an extensive literature review coupled to numerous field measurements. As part of this study water temperature was recorded in the bath, shower, washing machine and dish washer with changes investigated over time (cooling in a bath), space (different shower heights) and for different consumers. Cold water supply temperature varies as driven by seasonal factors, while hot water supply temperature remains relatively constant as controlled by a thermostat. The desired temperature was noted to remain relatively constant for a particular individual and would fluctuate between about 38°C and 42°C. The research provides insight into water temperature and presents useful inputs for modelling hot water enduses.”

(Citaat: Jacobs, H.E., Botha, B.E., Blokker, E.J.M. – Household Hot Water Temperature – An Analysis at End-Use Level – 1st International WDSA CCWI 2018 Joint Conference, Kingston, Ontario, Canada, 23-25 July – Vol1(2018) – 218)