This paper uses a detailed water end use data registry generated from the South East Queensland Residential End Use Study (SEQREUS) to examine (a) peak hourly and daily demand, and (b) water-related energy demand. The impact of water-efficient fixtures and appliances, as required by current building codes in Queensland, is also explored. The four peak demand days selected had increasing peak day factors of 1.3, 1.5, 1.6 and 1.7. The range of these values is slightly lower than those used in the Department of Environment and Resource Management (DERM) guidelines where the peak day factors range from 1.5 to 2.3, suggesting that the frequency and volume of peaking factors may be lower than those that are currently being used for network distribution design; due likely to the high penetration of water-efficient technology and growing water conservation awareness by consumers. This type of knowledge can facilitate the optimisation of infrastructure design and sizing and inform the subsequent deferral of such assets. In terms of water-related energy demand, it was found that the hot water components of showers, and to a lesser extent, taps and clothes washers were the most influential. Shower energy consumption for electric cylinder hot water systems (HWS) and solar electric-boosted HWS was 810 and 351 kWh/p/year, respectively. The type of hot water system was significant in dictating the volume of energy-related carbon emissions, with the results confirming the significant impact that electric storage water heating has on total household energy consumption and related carbon emissions. Substantial savings can be achieved by substituting water (eg, high star rating clothes washers and shower heads) and energy (eg, solar hot water system) efficient appliances in the home. Knowledge on the end uses that are influencing peak water and energy demand can: 1) facilitate the optimisation of infrastructure design and sizing and inform the decision process regarding subsequent deferral of these expensive assets; and 2) underpin future sustainability codes for new buildings.