The residential sector accounts for less than 8 percent of water used in the U.S., according to a recent study published by NAHB.
The recent NAHB study draws on information published by the U.S. Geological Survey (USGS). The USGS compiles data on water use every five years. The latest numbers (from 2010) were published in 2014. The USGS labels water used by residences as “domestic.” NAHB follows terminology more familiar to its readers and refers to water used by homes as “residential”
The 2014 USGS release shows that, in 2010, residential water use totaled 27,400 million gallons per day (Mgal/d). The significance of this number depends on your perspective. From the perspective of an individual utility, it can be very significant. Public suppliers like utilities withdrew 42,200 Mgal/d of water from its source in 2010, and over 56 percent of this was delivered to residential customers.
From a more holistic perspective that considers water used for all purposes, however, residential use constitutes a relatively small share of the nation’s thirst. Total withdrawals of water in U.S. in 2010 were 355,000 Mgal/d. The 27,400 Mgal/d used by residences accounts for 7.7 percent of this total.
Combined with data from the decennial Census, the USGS numbers imply that the average home in the U.S. uses about 260 gallons of water per day (gpd). However, the average varies from a low of 100 gpd in Maine to a high of 472 in Nevada. When the state averages are placed on a map, they show a distinct geographic pattern, with relatively low use per home in some upper Midwest and New England states, and higher use per home in the central South and West, especially in mountain and desert states.
NAHB used a statistical model to investigate several factors that may help explain the state-to-state differences. The basic results showed that, at the state level, water use per housing unit is positively correlated with average temperature and average household size, negatively correlated with annual rainfall. In short, homes tend to use more water if they are in states that are hot, dry and have larger households.
A complete description of the statistical model, along with a discussion of many other aspects of residential water use, can be found in the full NAHB study.