Shower systems, related hot-water systems and pipe losses dominate residential water-related energy. However, many time-based technological, behavioural and environmental factors influence water use and related energy consumption. This has meant that, to date, the performance of these systems has been relatively poorly understood. Here we build on earlier stationary modelling and analysis to develop and apply a Dynamic Water-Related Energy Material Flow Analysis Model in Households (DYNWAREHO). We use this to evaluate a highly monitored household to answer "What are the key energy pathways, their relative importance, and the key factors of influence, in household shower and hot-water supply systems? We explore how significantly hot-water losses can be influenced by showering behaviour and/or technological changes such as pipe insulation. We show that in the household studied, over 85% of the energy used for water heating flows as waste down the drain. Losses are the second largest energy user and account for more than 10% in the studied household. Energy use for actual "showering" accounts for less than 5% of the total. New technologies could influence this significantly. This result clarifies the significant wastage of energy inherent in the design and use of current shower systems. The analysis shows various options designed to improve design and management; it was made possible by the creation of the DYWAREHO model, applicable to any household, and calibrated on a specific Australian household. If acted upon through policy decisions and an appropriate design of shower and wastewater systems, the research can substantially improve the management of water-related energy. (C) 2019 Elsevier B.V. All rights reserved.