Tools- of Changes

On-Bill Feedback Lowers Water Use, but Not Email Feedback

This large-scale field randomized control trial found that feedback using per household comparisons achieved statistically significant reductions in consumption, but per capita comparisons had no effect. Of the groups receiving per household comparisons, the ones offered water-saving tips and free water-saving gadgets yielded the largest estimated reduction. The feedback was effective when provided in paper bills but not when provided by email.

This large-scale field randomized control trial (RCT) with around 712,000 metered customers tested different types of on-bill feedback. Customers began to receive the new bills from July 2021 and water consumption impacts were estimated over 12 months for each household. The authors randomly varied modules within the new bill to identify the impact that specific elements had on water consumption. They also compared these versions of the new bill to a fabricated control bill - a redesigned bill with behaviourally-informed modules stripped back or replaced by white space.

RESULTS

• Feedback with per household comparisons achieved statistically significant reductions in consumption compared to the control group. Conversely, per capita comparisons had no effect.
• Of the groups receiving per household comparisons, the ones offered water-saving tips and free water-saving gadgets yielded the largest estimated reduction of consumption (of roughly 0.5%).
• There was no impact on customers who received their bills electronically - probably because they were less likely to open and engage with their bills.
• While a reduction of 0.5% may seem small, total savings among the 712,000 customers were estimated at 250 million liters of water over the year. If all customers had been given the best-performing bill version, savings might have been up to 600 million liters per year.