This paper presents a novel energy balance scheme and performance indicators for assessing energy efficiency in water supply systems. This assessment consists of a three-step procedure: system characterisation and data collection, energy balance calculation and energy performance indicators assessment. The main innovation is the integrated approach between energy and water balances allowing the quantification of energy inefficiencies directly associated with water losses. Comprehensive energy performance indicators can be calculated by utilities with different maturity levels allowing a fair comparison of energy efficiency between systems with different layouts and operational schemes. This energy balance scheme has been applied by 17 water utilities in Portugal. Results have shown that systems provide more than twice the minimum energy necessary to supply their consumers and, consequently, there is a significant energy saving potential: 40% through water loss reduction, 30% for changes in network operation and layout and 30% for pump inefficiency reduction.

Water losses are responsible for increased energy consumption in water supply systems (WSS). The energy associated with water losses (EWL) is typically considered to be proportional to the water loss percentage obtained in water balances. However, this hypothesis is yet to be proved since flow does not vary linearly with headlosses in WSS. The aim of this paper is to validate the hypothesis, present real-life values for water-energy balance (WEB) components, and reference values for the key performance indicator that represents the ratio of total energy in excess (E3). This validation is achieved through the application of two approaches—top-down and bottom-up. The first approach requires minimum data, gives an overview of the main WEB components, and provides an effective diagnosis of energy inefficiencies through the calculation of E3 related to pumps, water losses, and networks. The second approach requires calibrated hydraulic models and provides a detailed assessment of the WEB components. Results allow the validation of the stated hypothesis as well as show that the most significant energy inefficiencies are associated with surplus energy, pumping, and water losses, each reaching up to 40% of total input energy. Less significant components are pipe friction and valve headlosses, each reaching up to 15% of total input energy.

The current paper is aimed at studying the influence of weather conditions on urban water consumption using available continuous flow measurements from existing District Metered Areas (DMA), belonging to different Portuguese water distribution systems. A three-step methodology was followed: Data processing; DMA segmentation in terms of billed consumption and socio-demographic characteristics; and Demand modeling. Cluster analysis was carried out to segment the different DMA with similar billed consumption and multiple linear regression analysis was used to describe the effect of weather variables (temperature and rainfall) on water consumption. Three well-defined DMA clusters were identified and the respective demand models were obtained for each group. Results have shown that temperature has a significant influence on water consumption, particularly in DMA in which the public billed consumption (29%) and the domestic billed consumption in the third and fourth tariff levels (10.7 and 10.1%, respectively) are relevant. The relationship between consumption and rainfall is not as evident as the relationship with temperature; however, the rainfall variable is equally important in the construction of demand models. These results allow improving monthly and seasonal network operation, since these allow a more robust profiling of the water uses as well as modeling demand for different weather conditions.