Saving energy with the hot water challenge

1. Motivation for and background to the hot water challenge

There is also considerable energy-saving potential in Switzerland. Reducing private energy consumption can make a fundamental contribution to achieving the federal government's goal of net zero emissions by 2050. Research shows that warm water is responsible for 15% of energy consumption in private households and 61% of it is heated with fossil fuels in Switzerland.

To investigate the potential of reducing private warm water consumption, Swiss Life Asset Managers, Livit Ltd and ETH Zurich conducted the warm water challenge from the beginning of October 2019 to the end of January 2020. 

2. What is the hot water challenge?

The hot water challenge is a project to investigate the possibilities of saving resources by reducing warm water consumption. The project involved the evaluation of data from over 4700 households throughout Switzerland. There were 3800 households that voluntarily took part in the challenge itself and were informed about their warm water consumption on a monthly basis.

The hot water challenge lasted four months, from the beginning of October 2019 to the end of January 2020. The aim was to reduce warm water consumption by 5% compared to September 2019.

3. Methodology and data protection 

The following behavioural economic components were used specifically for the hot water challenge: participating households received information on their own domestic warm water consumption, a set saving target, warm water savings tips, and they took part in a lottery. The lottery offered a prize of one month’s rent, whereby the winning household had to have met the 5% target to qualify for the prize. In addition, households received monthly feedback on their individual warm water consumption. They were able to decide individually in a self-determined manner which specific savings measures were to be implemented by individual households.

The participating households were examined in the form of a randomised control study, for which they were randomly divided into four experimental groups and one control group. This enabled an improved assessment of the individual effect of specific interventions.

All eligible households were first contacted by e-mail and informed about their intentions to investigate warm water consumption and the eligibility conditions for participation in the warm water challenge. Invitees who did not wish to participate were given the possibility of opting out via an “opt out” clause in the e-mail.

4. Results

The evaluation of the data collected over the duration of the challenge showed a positive influence on the warm water consumption of the participating households. Despite a seasonal absolute increase in their warm water consumption, it was significantly lower than for the households in the control group.

Behavioural economic incentives were also designed differently in the four experimental groups. The results showed that the social comparison with other participating households had a positive effect, while differences in the lottery had no effect. In addition, it was found that household cold water consumption also fell during the challenge period.

Even after completion of the challenge, the participating households still consumed significantly less warm water. Thus, there is a medium-term constant change in behaviour in the experimental group. A total of 2 000 000 litres of warm water were saved during the challenge, corresponding to some 39 tonnes of CO₂.

5. Conclusion 

The data analysis shows that the warm water challenge was successful: significant effects were observed during and after the intervention. The warm water challenge had a positive effect and significantly reduced the consumption of warm and cold water by the participating households compared to the control group. The overall target of a 5% saving among all households was not achieved, possibly due to the winter weather.

Nevertheless, the study offers valuable new insights into the potential for energy saving in private households. The study was very well received by the participating households and most of them would like to see the challenge continue. Together with the significant savings, these results make us very optimistic that the warm water challenge can make a meaningful contribution to achieving the climate targets.