national multiple family submetering and allocation billing program ...

submetered and five control (in-rent) apartments. Results from the submetered building yielded
encouraging average savings of 27% of water and wastewater use. This study prompted SPU to
conduct a study in 1996 comparing water usage in nine buildings (before and after submetering)
with different resident incomes, demographics, and building ages. Average water savings for the
nine apartments was 7.7% (8.5 gpd/unit) (Dietemann 1999). The most sizable savings were seen
with high water users. Of the nine buildings, seven showed savings, but in two buildings water
use increased. Dietemann attributed the variations in savings to include “time of year of water
use, high resident turnover, and master meter accuracy issues” (1999). Dietemann suggests that
controlling those variables, as well as a more complete analysis using control groups, would
allow for more generalized savings conclusions.
The National Apartment Association and the National Multi Housing Council
commissioned a study that examined 32 multi-family properties in Florida, Texas, and
California. The study included 14 in-rent, 9 submetered, and 9 RUBS properties. The study
attempted to quantify changes in water consumption due to different billing methods. In general,
it was found that residents that pay for water use less. Including common areas, the median
submetered property used 18-39 percent less water than in-rent properties and the median RUBS
property used 20-27 percent less than the in-rent sample. When common areas were excluded,
submetered properties used between 22-33% less water and RUBS properties used between 6-
22% less water. When submetered and RUBS properties were paired with in-rent properties
based on age, size, and location, the median submetered property used between 26 and 55
percent less water than its control pair. The RUBS property used similar water on a per capita
basis, but 32% less on a per occupied square foot basis. Intra-property results, which looked at
consumption in buildings before and after converting to a separate billing system, were less
conclusive (Koplow and Lownie 1999).
The Koplow and Lownie study, however, did not control for the installation of low-flow
fixtures in the sample selection process, nor report on any retrofits performed over the study.
The authors have clarified that the conserving impacts of plumbing retrofits were intentionally
included with the impacts of billing programs because of an observed linkage between retrofits
and billing program implementation. Income (or rent) was also excluded from the selection
criterion. In addition, participants were selected through an “outreach campaign”, rather than
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