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Evidence Base for Large-Scale Water Efficiency in Homes Phase II Interim Report (2010)

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This report comprises the first Waterwise developed in Phase II of the Evidence Base. It aims at helping water companies, manufacturers and retailers to build the case for their future water efficiency retrofitting projects and provides practical advice on how to make water efficiency a more viable option. It provides information on water savings achieved in water efficiency trials and projects across the UK, the uncertainties often innate to their findings, as well as CO2 emissions associated with water savings. It showed that water savings per property per day can be as high 34 litres, with uptake rates between 6 % and 22 %, and costs ranging from £41 to £240 per property.


I am delighted to introduce this report – the first of Phase II of the Evidence Base. The original Evidence Base report – in October 2008 – for which I also Chaired the Steering Group, was widely acknowledged to have been extremely useful in plugging the information gaps, and was used by both water companies and Ofwat during the 2009 Price Review.

However, the study posed almost as many questions as it has answered, which is why the UKEnvironment Minister’s Water Saving Group agreed that it should be kept updated. Consequently, a review was carried out to determine how the next phase of the Evidence Base, Phase II, could best assist the water industry, regulators and policymakers in supporting the development of water demand management options as resource options – including in the context of carbon targets.

Since the last Evidence Base report, Ofwat has introduced Water Efficiency Targets for the water companies in England and Wales and there is now a water efficiency duty on Scottish Water. There has been an increase in the scale of water efficiency projects being carried out. Six water companies were allowed investment for large-scale water efficiency programmes as part of Ofwat’s final determinationfor PR09, and other water companies are planning to carry out water efficiency schemes which are self- funded. This represents significant progress but delivering water efficiency continues to face significant opportunities and challenges, which this report highlights.

This report will help companies start to build the case for their future water efficiency retrofitting projects; for companies with the opportunity to plan during AMP5 and all companies during AMP6 in England and Wales and for Scottish Water. In future reports this will be supplemented with data from further domestic trials, but also from non-household areas of water efficiency such as from schools. The recommendations included in this report suggest ways that water companies, manufacturers and retailers can help to make water efficiency a more viable option. Waterwise will release a separate paper which will set out their views on and recommendations for water efficiency policy and regulation drawing specifically on this report. There are a number of areas where more work is required, but the results in this report should give water efficiency practitioners confidence that they can deliver water savings cost-effectively through retrofitting projects.

There is some fantastic work being carried out by UK water companies to take forward large-scale water efficiency, and this report not only draws on these to provide a solid evidence base, but will also influence future work, making it even more cost-effective. I am delighted too that this report contains a comprehensive analysis of the carbon and energy savings to be found in large-scale retrofitting.

I commend Waterwise for an extremely useful piece of work, and look forward to continuing to work with Waterwise and the Steering Group on this important project.

Summary of Findings and Recommendations

Several regions of the UK are already under serious water stress as a result of increasing population density, demographic change, increasing demand due to more intensive lifestyles and a climate in which extreme rainfall events and drought are becoming more and more prevalent. Future climate scenarios and population predictions suggest that more areas will be affected in the future.

In the past, there has been a perception in the water industry that there is insufficient evidence in the UK of the ability of water efficiency to deliver water savings cost-effective enough for it to be able to play its part in a twin track approach to water resource management, in which it contributes as a demand management measure alongside supply-side resource measures. In Ofwat’s final determination for PR09, six water companies in England and Wales were awarded funding for large- scale water efficiency programmes.

This shows that water efficiency does have an important role to play in helping the UK to meet these challenges. The Evidence Base represents the best current available knowledge of water efficiency in the UK. This report does the following:

Presents the robust, measured water savings from water efficiency trials and projects in the UK Explicitly details the uncertainty in the results and reveals structure in the distribution of water savings
Presents the typical costs involved in each trial

Develops a set of scenarios for large-scale water efficiency programmes, which include water savings, Average Incremental Cost (AIC) and Average Incremental Social Cost (AISC). Compares measured water savings to theoretical water savings to direct future savings estimates for water savings measures

Estimates carbon emissions and energy savings for each trial
Makes recommendations for further work for the Evidence Base and for key stakeholder groups

This report’s main findings are:

Water Savings

Measured water savings of up to 34 litres per property per day are possible from applying a multi- measure water efficiency retrofitting method in the traditional way, using current technology and means of engaging customers to encourage behaviour change. However, Anglian Water’s IpswichArea WEM trials resulted in savings of 41.5 lpd, which is the highest reduction in consumption of all the trials analysed in this report. There is a possibility that the fact that this WEM trial was carried out alongside a metering installation programme in the Ipswich area enhanced the results. Customers were made aware of their consumption and how much they could save by opting to be charged via a water meter, and this may have led to significant change in water-using behaviour.

Uptake rates

The results show a range of between 6% and 22% uptake rates for water efficiency trials carried out in general housing stock, whilst for social housing significantly higher uptake rates of between 45% and 60% have been achieved.