Rainwater Harvesting Systems (RHS) are increasingly used in buildings to mitigate water shortage and rising prices of centralised water supply. Notwithstanding the benefits of RHS, they may also promote adverse impacts mainly related to the high consumption of energy. In this context, energy intensity (i.e. unit of energy per unit of water) is a crucial parameter for assessing the environmental feasibility of different RHS. However, only recently has attention been drawn to the connection between water and energy consumption, which has been prompted by the increasing importance of water security, energy efficiency and economic feasibility. This connection, known as the water-energy nexus, has been increasingly acknowledged as a key principal for water planning. The objective of this study is twofold: (i) to review the energy intensity data reported for RHS; and (ii) to outline strategies to enhance the energy performance of RHS in buildings. For the reviewed literature, the median energy intensity of theoretical studies (0.20 kWh/m³) was considerably lower than that described in empirical studies (1.40 kWh/m³). This implies that theoretical assessments of energy intensity may not sufficiently consider the energy used for pump start-ups and standby mode, as well as the true motor and pump energy efficiency. However, to some extent, this difference may also represent the amount of energy that can be reduced by optimising RHS design and operation. When comparing RHS to conventional town water supply systems, the reviewed empirical studies showed that RHS tend to be three times more energy intensive, although optimised RHS can have more comparable values.Ultimately, it is predominately the local characteristics, such as rainwater demand, building type (single-storey or multi-storey), RHS sub-systems design, potable water plumbing system design, town water energy intensity, among other factors that will determine whether or not the environmental and economic performances of RHS are acceptable.

Advanced metering technologies coupled with informatics creates an opportunity to form digital multiutility service providers. These providers will be able to concurrently collect a customers' medium-high resolution water, electricity and gas demand data and provide user-friendly platforms to feed this information back to customers and supply/distribution utility organisations. Providers that can install low-cost integrative systems will reap the benefits of derived operational synergies and access to mass markets not bounded by historical city, state or country limits. This paper provides a vision of the required transformative process and features of an integrated multi-utility service provider covering the system architecture, opportunities and benefits, impediments and strategies, and business opportunities.The heart of the paper is focused on demonstrating data modelling processes and informatics opportunities for contemporaneously collected demand data, through illustrative examples and four informative water-energy nexus case studies. Finally, the paper provides an overview of the transformative R&D priorities to realise the vision.

Residential water heaters in Brisbane, Australia: thinking beyond technology selection to enhance energy efficiency and level of service Highlights: • Controlled electricity tariff enhanced the performance of water heating systems; • Night off-peak electricity tariff reduced the performance of water heating systems; • Solar water heaters are likely to be more resilient to Legionella sp. growth; • Water efficient washing machines may promote energy inefficiency.

Knowing water consumption patterns in buildings is key information for water planning. This article aims to characterize the water consumption pattern and water end-uses in low-income houses in the region of Florianópolis, Southern Brazil. Data were collected by interviewing householders, as well as by measuring the flow rate of existing water fixtures and appliances. The results indicated that the shower was the fixture with the largest water consumption in households, i.e., about 30%-36% of total water consumption on average, followed by the toilet (18%-20%). The surveyed households consumed from 111 to 152 L/capita·day on average, based on different income ranges. No correlation was found between income and water consumption. The results of this study can be used to estimate the consumption of water for new buildings, as well as to develop integrated water management strategies in low-income developments, in Florianópolis, such as water-saving plumbing fixtures, rainwater harvesting, and greywater reuse. Likely, there would be a deferral of capital investments in new water assets for enhancing water and wastewater services by saving water in low-income houses.