Residential Water Usage
AwwaRF Project 4031
Many water utilities are experiencing declining water sales among residential customers. Old rules of thumbs, for example households consume 100 gallons per day per person, are no longer sufficient as household water use predictions must account for competing factors. Company officials attribute the decline in usage to several possible factors including weather, the proliferation of new water-conserving appliances, changing household demographics, and classification anomalies, but a definitive cause has not been identified. This gradual erosion in residential consumption has resulted in increases in rates to provide sufficient revenues to meet service expansion projects and general maintenance demands.
The purpose of this research is to quantify changes in residential water use across North America observed during the past 30 years and identify contributing factors. To account for geographic and demographic variations, the research evaluated usage on national, regional and local levels. At each level, contacted utilities were asked to provide thirty years of annual residential usage data. To assess national trends, a random sample of 204 nationally representative utilities from the 1999 AwwaRF Financial/Revenue survey participants was contacted. On average, national level participants provided 15 years of residential water usage data.
Based on the information obtained, participating utilities are experiencing a general downward trend in water usage by single-family accounts. Preliminary results show that on average, single-family residential customer water usage has reduced by 613 gallons per year (or ~0.8% based on 78,186 gallons as the average annual water usage for 2005) or approximately 50 gallons per month. If this trend were to continue for the next 20 years, the average annual water usage would be about 65,750 gallons per year or about 15% less than current usage.
To assess regional variations, eleven partner utilities participated in a more in depth analysis of their customer water usage patterns. Beyond the annual residential usage data, partners provided information pertaining to peak day/hour, water leakage estimates, conservation policies, historic rate structures, water quality and operation statistics. As examples, water poor communities often employ sophisticated water conservation policies and strict irrigation policies, while promoting water fixture replacement programs. While water rich areas may only provide water conservation educational materials and/or offer leak detection programs.
At the local level, the study is assessing the affects of water conservation fixtures and individual household demographics on water consumption through two phases: a household survey and a two-week data logging. Based on the approximately 300 survey responses of customers in the Louisville area, about 25% have at least one ultra-low flush toilet and one low-flow showerhead, about 60% have undertaken a remodel since 1994 and should have low flow bathroom/kitchen fixtures and three-quarters of the houses are comprised of at least two people. The data logging results are still being analyzed.
This research initiative will provide an up-to-date and comprehensive assessment of changing water use patterns by national, regional, and local levels. This will provide utilities with better tools to estimate water usage and to modify pricing structures. In this manner, utilities can have better financial models to predict revenues.