The Water and Energy Implications of Bathing and Showering Behaviours and Technologies (2009)
This review was written by Gareth Walker, Research Associate, and edited by Joanne Zygmunt, Head of Research.
The purpose of this review carried out by Waterwise is to identify gaps in knowledge and understanding of personal washing, focussing on showering and bathing in particular because of their high contribution to per capita water consumption. The study seeks to inform and improve demand management programmes, regulation and policy decisions in managing demand. The review utilises published materials from various literature sources. Gaps in knowledge exist regarding basic aspects such as the frequency and duration of showers and bath use; determination of appropriate weightings for shower performance variables; and messaging to effectively market bathroom appliances.
Knowledge of the drivers of showering and bathing behaviour must be developed
A review of evidence on showering and bathing patterns inside the home revealed an extremely high variance in basic factors such as frequency of use for showers and baths, and duration of use for showers. Research exploring the interaction between shower and bath use is limited, as is research which seeks to identify and describe the factors which control how frequently a bath or shower is used, and the volume of hot and cold water used in each event. Research which focuses on user attitudes and perceptions, their relation to behavioural patterns in the home, and the interaction between different users and different appliances should be carried out in order to underpin any behavioural or technological change campaigns.
Performance indicators and baselines for acceptance must be further developed in showers
Past research has identified variables which can be used to describe shower performance, such as spray pattern, skin pressure, temperature consistency etc. What have yet to be investigated fully are the relative weightings of these variables according to user preferences. To successfully transform the showering market towards water efficiency, good performance must be guaranteed in order to address current public concerns over the quality of water efficient appliances and to avoid customers rejecting new technologies. Research should trial various designs of low flow shower systems and identify where the risk of underperformance rests. In turn, an enforceable, recognised, minimum standard for performance in showers would help to encourage public confidence in efficient showers and would compliment any planned water efficiency labelling scheme.
Product development and marketing must not rely on environmental messaging
Marketing an appliance as water efficient may significantly limit its market without additional messaging. Research into current factors which affect bathroom fitting purchases emphasise price, appearance, and performance over water consumption. Shower systems which employ all of these messages in conjunction are more likely to see success. A showerhead which has been designed according to customer specifications of performance and marketed as “advanced” or “optimised” will fare better than onelabelled as “water efficient”, which is still associated with poor performance in many people’s perceptions.When water efficient showers can be elevated in terms of social status and performance to the level power showers currently enjoy, water efficient showering will become an aspiration rather than a compromise.
An upgrade in plumbing and shower technology may lead to the need/opportunity to replace electric showers
Evidence suggests that around 40-50 % of showers installed in the UK are electric showers, most likely due to their being relatively self-contained in terms of water pressure and hot water supply, and so well suited to retrofits and bath replacement. Electric showers present a difficult trade-off between water, energy, and carbon consumption. Flow rates and therefore hot water and energy consumption tend to be lower, and there may be an additional advantage to heating at point of use due to cutting storage losses for hot water. However, the carbon weighting of electricity per unit of energy is significantly higher than gas, meaning that electric showers tend to out-perform in terms of water and energy, but might not in term of carbon. There is perhaps less room for product development in electric showers, with significant savings attributed more to behavioural change. Holding the carbon weighting of gas and electricity constant, replacing electric showers with efficient mixer showers of comparable flow rates may prove to be a valid long-term goal in homes with sufficient water pressure. Increased water pressure may be introduced through the combined upgrade of a conventional open/vented boiler with an unvented boiler, such as combination boilers, and a high efficiency mixer shower then introduced.
Population growth, development, lifestyle changes as well as climate changes will necessitate – in fact already require – a reduction in water demand.
A large proportion of household water use is attributed to ‘personal washing’, which includes showering, bathing and in some cases basin tap use; these account for about one-third of water use in homes and are the largest growth areas of domestic water consumption according to many water company resource plans. For this reason, water efficiency programmes that have long targeted toilet flushing are now beginning to target personal washing.
What is of concern is that much less is understood about personal washing than toilet flushing. Anecdotal evidence suggests that personal washing technologies may interact with user behaviours in such a way as to produce unexpected results; for example, more efficient showerheads may lead to an increase in the duration of showers, resulting in the same volume of use or even an increase in net use. A more thorough understanding of personal washing and specifically of the dynamic between technologies and behaviours will help to inform water demand management strategies and hopefully increase their effectiveness, thus contributing to a more stable supply/demand balance and a healthier natural environment. Any reductions in water use, particularly in hot water use, will translate into energy savings and so into reductions in greenhouse gas emissions; about one percent of total UK green house gas emissions are attributed to clean water supply and treatment, wastewater collection and treatment, and about five percent is attributable to heating of water in homes (Defra 2008).
Purpose and aim
The purpose of this review is to identify gaps in knowledge and understanding of personal washing, focussing on showering and bathing in particular because of their contribution to per capita consumption. Basin taps have been purposely left out in part because little research exists on the component, especially with regard to the interaction between basin taps and showers and baths, and in part because the contribution of basin taps to consumption is less of a concern than showering and bathing.
This review aims to synthesize the existing evidence base on showering and bathing in order to provide recommendations for its strengthening so that demand management programmes, regulation and policy decisions are as effective as possible in managing demand.
This report attempts to synthesize published materials from a variety of sources including government and the water industry. More evidence likely could have been gleaned from academia, but resource limitations prevented a comprehensive review. The author is aware of a handful of studies that will contribute significantly to the understanding of showering, but these studies are yet to be published. In addition, the author has reviewed some unpublished data from, for example, the British Library and water companies. Draft Water Resource Management Plans have also been reviewed, but are subject to revision as only a limited number of plans were available at the time of reviewing and may have since been updated.
Structure, theory and uncertainties
The report is divided into several tasks that when taken together provide an overview of bathing and showering. This division is based on a simplified version of Kurz et al’s (2002) model of behaviour- technology interactions and resulting resource consumptions (figure 1). Kurz’s model aims to extend beyond traditional choice models, i.e. of utility maximization, by accounting for limited rationality, rebound effects and prior conditions.