The increasing energy intensity of drinking water supply

Abstract

Supplying water to cities is an energy-intensive activity, but few longitudinal studies exist of water utilities’ energy intensity (energy use per unit water volume). Using t-tests and regression on public records from the state of Wisconsin, USA, we analyze over 500 drinking water utilities’ performance from 2001 to 2020. This is the first long-term panel analysis of its kind. The annual data show energy intensity has increased by 12 % in large, 8 % in medium, and 28 % in small water utilities. The large utilities remain the least energy intensive (0.49 kWh/m³ as of 2020, compared to 0.53 kWh/m³ and 0.67 kWh/m³ for medium and small utilities), and the small ones have diverged the most from the other two. At the same trajectory, energy intensity will increase by another 27 % for small water systems by 2040. Our analysis demonstrates economies of scale, highlights disadvantages of small utilities, and confirms predictions that water services would become more energy intensive. It motivates sustainability of coupled energy and water infrastructure and emphasizes responsible use of natural resources.