Nonresidential water use is a volumetric measure of the use of publicly-supplied (municipal) water for areas other than residential use. It is typically subcategorized under users including Commercial, Industrial, and Institutional sub-sectors, which are often jointly designated as the ICI or CII sector.
Estimates of total CII use In the United States, a USGS nationwide compilation of public supply withdrawals and deliveries indicates that in 2010 the total daily volume of nonresidential use was approximately 12,000 million gallons per day (mgd) and accounted for about 29 percent of public supply withdrawals (or 45 gallons per capita per day when divided by the estimated 268 million people who relied on public-supply water). This estimate is obtained by subtracting from total public supply freshwater withdrawals (41,700 mgd) the reported domestic (residential) use (23,800 mgd) and allowing for 14 percent of unaccounted for water (because of leaks, hydrant flushing, tower maintenance, and other system losses, also called non-revenue water). The estimates of average water loss in public supply systems in the U.S. range from 12 to 16 percent.. Summarizes the water loss percentages reported by 110 municipal respondents with the average and median reported values, respectively, were 12.1 percent and 9.9 percent The share of CII use varies across water utilities; in a sample of 31 utilities in Texas it ranged from less than 4 percent of metered use in Lamar County WSD to 79 percent in Borger MWS, with average share of 35 percent. In order to achieve improvements in the efficiency of CII water use, it is necessary to obtain information about the existing conservation potential in different types of establishments and about specific end uses of water in each CII category. Studies of water use in the CII sector were conducted by the American Water Works Association, Pacific Institute, Colorado WaterWise Council, Conserve Florida Water Clearinghouse (CFWC), and The Water Research Foundation (WRF).
CII user categories and subcategories
Nearly a hundred specific end uses within seven major groupings (i.e., washing and sanitation, domestic-type uses, landscape irrigation, outdoor and indoor water features, cooling and heating, food service, and process water) were compiled in the WRF study. Typically, the total CII use in an urban area or a region is broken down by categories of commercial establishments (and types of institutions or industrial plants) based on the kinds of goods and services provided, or their function. The category's water use is then separated into several end uses (or purposes). The following list of 14 major CII categories of nonresidential buildings or establishments (with examples of possible subcategories) are commonly found in an urban water service area of a public water supplier (or water utility):
Establishments/sites with a dominant water end use: commercial/industrial laundries, laundromats, car washes, city parks and recreation areas, public pools and water parks, golf courses, irrigated landscape areas. Office buildings: large offices w/cooling towers, office complexes w/irrigation, small office buildings. Lodging places: hotels, motels and inns, resort hotels (with and without irrigation and cooling). Eating places: full-service restaurants, fast food outlets, bakeries and cafeterias, bars and clubs. Food sales: grocery stores and supermarkets, convenience stores. Retail outlets: retail stores, strip shopping centers and enclosed malls, liquor stores. Schools: pre-schools and day care, primary and secondary schools, university/college campuses. Health care: hospitals and sanitariums, medical centers, doctor offices, laboratories. Service: auto service (auto sales, gas stations, auto repair shops), personal services. Public assembly buildings: community centers, meeting halls, convention centers, health clubs, bowling alleys, ice rinks, museums, theaters, cinemas, sports arenas, libraries, funeral homes, exhibition halls. Public order and safety facilities: police stations, fire stations, prison, reformatory, or penitentiary, courthouse or probation office Religious buildings: churches, synagogues, monasteries, mosques, sanctuaries. Elderly care facilities: retirement homes, residential care/assisted living, hospices. Manufacturing: heavy industry, light industry, food and beverage processing, machine shops.
These CII categories and subcategories account for a high percentage of the total CII use. Some of these building/establishment types are identified at some levels of aggregation of the North American Industry Classification System (NAICS) and former Standard Industrial Classification (SIC) codes. Also, the Energy Information Administration (EIA) identified 85 types of commercial buildings and facilities which were grouped into 16 general categories. Many of these overlap with the list of 14 groupings listed above.
Water use metrics and benchmarks
Water conservation planners (at water utilities) and CII customers use several metrics of water use (and their associated benchmarks) in order to assess their success in achieving water use efficiency goals. A “metric” (or “performance indicator”) is a unit of measure (based on a formula) that can be used to calculate the rate of water use during a given period of time (and at a given level of data aggregation). A “benchmark” is a particular (numerical) value of a metric that denotes a specific level of performance, such as a water-use efficiency target. When quantifying water use in the CII sector, the total volume of consumption (over any given time interval) at any given CII facility is “normalized” by the scale of water-using activity, which corresponds to the rate at which water is used (also referred to as water use intensity or WUI). Two scaling factors (or "proxy" measures of scale), the number of employees and the square footage of buildings (or facilities) are commonly used in the CII sector because the employment and floor space data are generally available. Examples of the corresponding proxy metrics are: water use per employee in manufacturing plants, or water use per square foot in office buildings. However, more appropriate are "functional" metrics such as water use per occupied room in hotels, or water use per meal served in restaurants, since they are linked more directly to water use. National surveys of commercial buildings by the U.S. DOE Energy Information Administration and EPA Energy Star provided proxy metrics data on the mean and median values of water use per square foot of buildings floor space. The median values are useful when placing water use in a CII establishment among its peers because the sample distributions typically have a pronounced right tail skew. Mean (or average) values are useful to planners who need to estimate total category use based on results from a sample of establishments.
Water utilities often adopt water efficiency programs that are directed specifically to CII customers. The programs often target the largest water users as well as specific categories of CII customers including government and municipal buildings, large landscape areas, schools and colleges, office buildings, restaurants and hotels. Water use information in these and other readily recognizable functional classes of CII users from several studies of the CII sector are briefly characterized below.
Water use in major CII categories
Office buildings In the U.S. cities, the share of the total CII use of water in office buildings ranges from 12 percent (in Tampa, Florida) to 30 percent (in New York City). The three largest uses of water in office buildings include restrooms, heating and cooling, and landscape watering. The reported proxy metrics of water use intensity (WUI) for office buildings range from 25 gallons/1000 square feet/day (g/ksf/d) to 129 g/ksf/d with reported weighted average use from eight utilities from Florida and Texas of 88 g/ksf/d. The reported median values range from 34 g/ksf/d to 62 g/ksf/d. Estimates of average daily use per employee range from 9 gallons/employee/day (ged) to 18 ged with the median value of 13 ged in the EPA’s Energy Star Portfolio Manager data.. Nationwide, there are approximately 1,012 thousand office buildings with a combined floor space of 1,952 million square feet.EIA CBECS Assuming the WUI of 88 g/ksf/d as representing average office usage in the U.S., the total country-wide use would be 1,400 mgd or close to 12 percent of CII use. Significant quantities of water can be saved in older office buildings by replacing bathroom fixtures, cooling tower efficiency retrofits, and adopting efficient landscape irrigation measures. Estimates of potential water conservation savings range from 19 percent in southwest Florida to 30 percent or more in California.
Retail outlets Retail (also classified under mercantile or commerce) includes retail stores, vehicle dealerships, strip shopping centers, and enclosed malls. Retail outlets account for significant percentage of CII use; examples include 4 percent in Oakland CA (East Bay MUD), 5 percent in Austin TX, about 15 percent in Tampa FL, 17 percent in Phoenix AZ, and 20 percent in New York City. The major end uses in retail stores are space cooling, restrooms and landscape irrigation. The reported proxy metrics on water use intensity in retail outlets include an estimate of 122 gallons/1000 square feet/day (g/ksf/d) in Phoenix AZ, 40 g/ksf/d in Santa Fe NM, and 98 g/ksf/d for one-story stores and 115 g/ksf/d for community shopping centers based on data from eight utilities in Florida and Texas. According to the EIA survey there are 438 thousand retail stores (other than malls) and 164 thousand enclosed and strip malls in the U.S. Their estimated total floor space is, respectively, 5,439 and 5,890 million square feet. Assuming the WUI of 98 g/ksf/d for retail stores and 115 g/ksf/d for shopping centers, the combined use of retail outlets in the U.S. would be 1,210 mgd or 10 percent of total CII use.
Restaurants Restaurants (and fast food places) account for about 3 percent of total CII use in Austin, Texas and 5 percent in Oakland, California (EBMUD) and up to 8 percent in the State of Florida. The largest uses of water in restaurants result from kitchen activities such as washing dishes, making ice, and preparing food. A significant amount of water is also used for restrooms. The proxy metrics data show WUIs in restaurants ranging from 474 to 578 g/ksf/d in selected Colorado utilities, an average of 589 g/ksf/d in Austin, Texas,, as referenced in and 670 g/ksf/d in Florida. Somewhat wider range of 356 to 907 g/ksf/d was reported in an earlier study. Data on functional metrics suggests that restaurants would use around 6 to 9 gallons of water per meal served, 20 to 31 gallons per seat per day, and 86 to 122 gallons per employee per day. Other studies reported 17 gallons/seat/day in Santa Fe, New Mexico and 29 gallons/seat per day in Colorado utilities.
Given the total floor space of 380 thousand food service buildings of 1,819 million square feet and assuming average use of 521 g/ksf/d, the total U.S.-wide use in restaurants would be 950 mgd or close to 8 percent of CII use. Restaurants can save significant amounts of water by maximizing the efficiency of pre-rinse spray valves, food disposal systems and upgrading dishwashers, ice machines, and steam cookers to Energy Star® qualified models that use less water.
Schools The shares of total CII use in schools range from 3.5 percent in Phoenix, Arizona to 6.5 percent in Tampa, Florida and up to 8 percent in Oakland, California. Most schools use water for restrooms, cooling and heating, irrigation of outdoor playing fields and lawns, locker rooms, laboratories, and cafeteria kitchens.