Consumption Feedback and Water Saving: A Field Intervention Evaluation in the Metropolitan Area of Milan

This paper investigates whether informative feedback on consumption can nudge water saving. We launched a five-month online information campaign which involved around 1,000 households located in the province of Milan (Italy) with a smart meter. A group of households received monthly reports via email on their per capita daily average water consumption, including a social comparison component. The Intention to Treat (ITT) analysis shows that, compared to a benchmark group, the units exposed to the intervention reduced their per capita water consumption by around 6% (25.8 liters per day or 6.8 gallons). Being able to observe the email opening rate, we find that the ITT effect is mainly driven by complying units. Through an Instrumental Variable approach, we estimated a Local Average Treatment Effect equal to 54.9 liters per day of water saving. A further Regression Discontinuity Design analysis shows that different feedback on consumption class size differentially affected water saving at the margin. We also found that the additional water saving increased with the number of monthly reports, though it did not persist two months after the campaign expired.