national multiple family submetering and allocation billing program ...

commodity charge for water and wastewater. Properties built before 1995 used 11.4 kgal per unit
more than properties built after 1995 – this is presumably largely the result of the high efficient
plumbing fixtures (toilets, showerheads, and faucet aerators) mandated for new construction by
the 1992 Energy Policy Act (EPACT). The average number of bedrooms per unit is a reasonable
surrogate for the number of people living in each dwelling unit. These models suggest that for
every additional bedroom water use is increased by an average of about 18.2 kgal per unit.
Properties that reported having a play area used 6.5 kgal per unit more than properties without
that amenity. The presence of a cooling tower increased per unit water use 9.9 kgal per unit. For
every dollar more that a utility charged per thousand gallons of water and wastewater, a
property’s water use would decrease by 1.8 kgal per unit per year.
It should be noted that all of the beta coefficients in Table 5.19 are additive and provide a
method to estimate annual water usage for a given property. The generic equation for Model #3
follows the same logic as was outlined in the section on Model #1. For example, if there is a
property that was built before 1995, has a cooling tower, is submetered, has an average
commodity charge of $3 per kgal, and has 1 bedroom, the following equation could be used:
27 .37 + 11.40 + 9.85 −10.05
+ 3*( −1.76)
+ 1*(18.18) = 51.47
From the Model #3 equation, the annual water use could be estimated for the property as
51.47 kgal per unit per year.
Matched-Pair Analysis
As described in Chapter 3, the purpose of the matched pair analysis was to identify pairs
or triads of properties within a single geographic area that differed in billing type but held
constant as many building characteristics as possible that could influence water use. By
augmenting the larger statistical analyses with this smaller more controlled study, we were able
to test some of the prior findings “on the ground” by verifying at each site important
characteristics of the match before testing the difference in water consumption for properties
whose residents paid under different billing systems.
Because of the limited number of impact properties to choose from in any single
jurisdiction, it was not possible to select pairs that were similar on scores of characteristics. All
pairs were in the same jurisdiction which held external use factors constant such as weather,
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