The Impact of Excess Water Use Charges in Christchurch

Michele McDonald – Christchurch City Council

The Christchurch City Council introduced an excess water supply residential targeted rate in its 2021-31 Long Term Plan. The additional water use charge responded to ongoing calls for volumetric charging to support water demand management after excess use charges were removed for residential customers in 1989 when the city was amalgamated with Banks Peninsula.

The excess water supply residential targeted rate created much controversy about the fairness of a uniform water allowance and its impact on the garden city image. However, it also prompted customers to find and repair leaks and to be more mindful of their garden watering habits in order to avoid paying extra for water. This positive change in customer behavior has resulted in huge water demand savings over the past two summers. The 30% reduced peak water demand exceeds Council’s predicted water demand savings and is equivalent to the production capacity of 9 medium-sized water supply pump stations. Because up to 50% of residential water was used by only 20% of customers, the majority of residents were not adversely affected by the new excess water use charge. 

The immediate benefits of the reduced summer peak demands were reduced energy costs and avoided water restrictions that would have been needed because of ongoing capital improvement projects. If the change in the garden watering habits of Christchurch residents can be sustained, water supply capacity will be released to accommodate growth and provide significant capital and operating cost savings to existing and future Christchurch residents.

The policy provides for residential excess water use to be charged at a fixed rate of $1.35 for every 1,000 litres of water used in excess of the daily allowance. Responding to 191 submissions, the Christchurch City Council adopted a change in the excess water supply residential targeted rate to increase the average daily water allowance from 700 to 900 litres as of 1 July 2023. This change will allow the garden city residents to use more water than the average New Zealander. 

This paper outlines the Christchurch City Council journey towards excess water supply residential targeted rates and provides the detail of the water demand savings experienced over the past two summers. The benefits of continuing to charge excess residential water use are noted whilst recognizing that an increased daily water allowance will likely impact the water consumption in the next peak demand season