Saving water at Cape Town schools by using smart metering and behavioural change
Last registered on June 04, 2019


Trial Information
General Information
Saving water at Cape Town schools by using smart metering and behavioural change
Initial registration date
June 03, 2019
Last updated
June 04, 2019 12:12 PM EDT
Primary Investigator
School of Economics, University of Cape Town
Other Primary Investigator(s)
Additional Trial Information
Start date
End date
Secondary IDs
The city of Cape Town suffered a severe water crisis in 2018. At the peak of the drought in South Africa’s Western Cape, a randomised control trial over four months at 105 schools investigated the impact of two behavioural interventions to encourage responsible water usage: feedback in the form of detailed and customised water usage data from smart meters, and an interschool competition. Difference-in-differences analysis showed that the interventions reduced water usage in these schools by 16 to 27%. The information feedback was found to be more effective in reducing night time water use, indicating better water usage by the staff, while the competition was found to be more effective during the day time, indicating better water usage by the pupils. The contrast highlights the way feedback signalling was understood differently by the two groups, with different effects on their assumption of responsibility. This example from Cape Town schools demonstrates the effectiveness of combining smart technologies with behavioural insights and nudges. It provides a model of water conservation interventions for sustainable cities.
External Link(s)
Registration Citation
Visser, Martine. 2019. "Saving water at Cape Town schools by using smart metering and behavioural change." AEA RCT Registry. June 04.
Former Citation
Visser, Martine. 2019. "Saving water at Cape Town schools by using smart metering and behavioural change." AEA RCT Registry. June 04.
Experimental Details
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
School water usage
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
A randomised control trial (RCT) was used to evaluate the impact of two behavioural interventions: (1) usage feedback and (2) an inter-school social comparison based on water usage in schools. After installation of smart water meters, all schools received a once-off leak detection and maintenance upgrade. Thereafter, the schools underwent a nine-week baseline period before treatments were applied.

This study contains a control group and two treatment groups:
Control group: Schools received smart meter installation, but no feedback on their usage.

Treatment group 1 (T1 - Feedback): Schools received feedback about their daily and weekly usage. Weekly usage reports were emailed and sent via text message to the principal and two additional staff members. Principals were encouraged to share this information with learners during weekly assemblies. In addition, schools received a pre-designed poster that could be updated with the latest water usage information on a weekly basis. The poster was put next to a school’s notice board with the intention of improving information transition from staff to pupils.

Treatment group 2 (T2 - Social comparison): Schools received the same feedback information as treatment group 1 along with comparative feedback on their water usage relative to other schools. The social comparison treatment consisted of a leader board of schools based on percentage water savings relative to the pre-intervention baseline. The leader board was updated weekly. As in T1, schools received a pre-designed poster on which usage information could be updated weekly.

Feedback reports were sent on Monday mornings on a weekly basis. Many of the schools did not have reliable internet access, thus treatment had to be applied through reports rather than through the use of an online portal in order to ensure equality of treatment across schools.

The schools entered the study in three waves with interventions starting on 15 April 2018, 3 June 2018 and 22 July 2018. This stepped approach to treatment implementation was necessary firstly because the severity of the drought made water saving a top priority and the City of Cape Town and corporate funders of the intervention wanted feedback reports as soon as possible, and secondly because installing the smart water meters and doing the maintenance work was a lengthy process.
Experimental Design Details
Randomization Method
Schools were randomly allocated to either of the treatment groups or control group on the basis of usage in the pre-intervention baseline period and stratified on usage terciles to ensure that schools across the usage distribution were equally distributed among the groups. Randomisation was done in STATA 14.
Randomization Unit
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
120 Schools
Sample size: planned number of observations
750,000 litres/30min water usage
Sample size (or number of clusters) by treatment arms
36 Schools Control, 40 Schools information feedback, 44 schools information feedback and social comparison
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
IRB Approval Date
IRB Approval Number
Post Trial Information
Study Withdrawal
Is the intervention completed?
Intervention Completion Date
September 30, 2018, 12:00 AM +00:00
Is data collection complete?
Data Collection Completion Date
October 31, 2018, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
105 Schools
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
679,649 litres/30min water usage
Final Sample Size (or Number of Clusters) by Treatment Arms
30 Schools Control, 33 Schools information feedback, 42 schools information feedback and social comparison
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers