Water efficient appliances play an important role in water conservation. Water utilities and researchers have mostly relied on small-scale randomized control trials with uncertain external validity to evaluate the effectiveness of these appliances. In this paper, we study a nation-wide program, the Home Improvement Programme (HIP) with an optional upgrade of bathrooms, to provide insights on the effect of efficiency improving programs on residential water consumption.

In Singapore, there are more than one million HDB flats housing close to 80% of the population. HIP is an upgrading program, introduced in 2007, to resolve common maintenance problems of aging HDB flats. As of December 2019, 55% of all HDB blocks were eligible for HIP, out of which 56% had completed the upgrade. Using monthly water billing data for all HDB flats from 2011 to 2019, we employ a staggered difference-in-difference regression approach to evaluate the average treatment effect of HIP on water consumption. We further study the evolution of the treatment effect and the heterogeneous effect by housing characteristics and mean consumption quartiles. We also investigate how the effect of water efficient appliances interacts with extreme environmental conditions, such as excessive heat, rainfall, and air pollution.