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RESULTS FROM AN ENERGY-EFFICIENT SHOWERHEAD FIELD STUDY
PREPARED BY PACIFIC NORTHWEST LABORATORY
The Bonneville Power Administration (Bonneville) initiated research to determine the energy saving potential of energy-efficient showerheads. The research was implemented in several phases by the Pacific Northwest Laboratory (PNL). The first phase was a field study designed to identify field conditions associated with the installation of, and potential savings from, energy-efficient showerheads. Bonneville collected energy use data from field study participants concurrent with this field study to use in the second phase of energy savings analysis. This report is limited to the first phase field study.
A total of 150 single-family Regional End-Use Metering Program (REMP) sites were eligible for participation in this study (out of 154 in REMP). The sites are located in Oregon, Washington, Idaho, and Western Montana, and, although probably not statistically representative of the region, they include a cross section of residences and occupants. To recruit field-study participants, residents were offered a $40 cash incentive, free showerheads, free professional installation, and a return of their old showerheads upon request.
Savings from energy-efficient showerheads depend on several program factors, including participation in a retrofit program, replacement of high-flow showerheads with energy-efficient showerheads, and use of the retrofit showerheads for bathing. Savings are dependent on field conditions, such as existing water flow rates, water pressure, and type of water system. A summary of field study results on these topics is provided below.
PROGRAM AND MEASURE RESULTS
The savings from retrofit programs depend on both participation in the program and installation of measures. Many homes have more than one shower. Consequently, results need to distinguish between number of homes in the program and number of showerheads.
Program participation rate is the number of showerheads distributed to the program participants. Of the 150 sites eligible to participate in this study, 111 elected to participate. However, seven withdrew, for a total of 105 who participated in the site visit. Six homes dropped out during the site visits, resulting in a 65% program participation rate. Program participation factors are further explained in Table S.1.
Program penetration is defined as the fraction of participants who actually had showerheads installed. Ninety-eight of the initial 111 households who volunteered to participate were retrofit with energy-efficient showerheads for an 88% program participation rate.
Program persistence is based on the fraction of the households that installed showerheads, where at least one showerhead remained in service. After 15 months, 92 of the 98 homes that were retrofitted retained at least one showerhead for a 94% program persistence rate.
Measure participation is based on the actual number of showerheads distributed compared to the total number that could be installed. In this study, it is estimated that the original 150 potential participants had 240 showerheads. Of the 240, 158 were replaced for an approximate measure participation of 66%.
Measure penetration is based on the number of efficient showerheads installed compared to the number that could have been installed. Of the total 161 showerheads in the 98 participant homes, 158 showerheads were replaced for a measure penetration of 98% for the 98 homes and 66% for the 150 original.
Measure persistence is based on the fraction of measures that remain in service compared to the number installed. Of the 158 showerheads that were installed in the 98 homes, 149 remained in service after 15 months for a 94% measure persistence rate.
TABLE S.1. Program Participation History
Energy savings from retrofit showerheads result from reduced hot water use. This field study measured actual water flow rates to assess energy savings potential. Energy-efficient showerheads rated at 2.5 gallons per minute (brand name Ondine) and 2.0 gpm (brand name ETL) were retrofit in this study. Flow rates and changes are provided in Table S.2.
Energy-efficient showerheads effectively reduced water flows. However, the average 44% flow rate reduction masked a wide variation that included flow increases at 15% of the ETL sites and 23% of the Ondine sites. Low water pressure was associated with these sites (<1.34 gpm).
Twenty percent of the participants had wells. The average water pressure for well-supplied homes was 37.9 pounds per square inch (psi), as compared to 66.1 psi for city-supplied homes.
TABLE S.2. Average Water Flow Results (in gpm)
Showering frequency is another key factor in showerhead savings. Survey responses indicate showering is the major form of bathing with 69% of the showers being used "frequently" (at least four times weekly). In sites that had 2 showers, 71% of those replaced were said to be used frequently. In sites that had 3 showers, 52% of those replaced were said to be used frequently.
These specific field study results are not significantly different from results reported elsewhere in the Pacific Northwest. However, showerhead savings potential appears to be less than initial expectations--especially the finding that pre-retrofit flow rates are close to 3 gpm rather than 5 gpm and that roughly 20% of retrofit showerheads actually show increased flows. Further, this study used a very aggressive design yet managed to convert two-thirds of the potential showerheads instead of the 85-90% expected. The cumulative effect of lower-than-expected flow reductions and retrofit rates is savings that are 65-70% less than the anticipated 2.5 gpm flow reductions and 85-90% retrofit rates initially expected.
This field study is based on a relatively small sample of single-family homes. Results from this study are not necessarily representative of the Pacific Northwest region or other types of residences. Nevertheless, this research is the most comprehensive undertaken in the region to date, and represents the best source of information for Bonneville's program planning and evaluation.
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