With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
All toilets and most showerheads today meet the federal water-efficiency standards, but not all of these products perform satisfactorily. With toilets and showerheads, we include products that meet or exceed WaterSense standards, which includes performance requirements—although we go beyond WaterSense where there are issues not adequately addressed by the program. We also look for other products that conserve potable water, such as rainwater catchment and graywater recovery and reuse systems.
Delta Faucet Company offers residential water-efficient showerheads with H2Okinetic Technology that use only 1.5 gallons per minute yet deliver a satisfying shower. The showerhead provides 36% water savings over standard 2.5 gpm showerheads; this saves both water and energy (for heating water). The showerhead produces water droplets that are fairly large, resulting in good heat retention and body wetting. Most low-flow showerheads either create very small droplets or aerate the water.
Showers account for about 17% of all indoor residential water use, according to the EPA. Inefficient showerheads increase water and energy use, but some newer low-flow units have been faulted for delivering poor performance, leading people to spend more time in the shower, or remove the showerhead and replace it with an older, much higher-flow showerhead.
WaterSense has developed a specification that includes water efficiency, spray force, and spray coverage criteria. The first criterion is designed to reduce water use; the last two are aimed at maintaining a standard for superior shower performance, even as less water is being used. After doing field research in 2008, WaterSense developed tests that measure performance in spray force and spray coverage. Not directly included in the WaterSense criteria is “wetting performance” (though spray coverage could be a proxy for that) and “heat retention,” which is a function of droplet size. Showerheads that atomize water into very small droplets cool off very quickly, though atomizing showerheads may or may not satisfy the “spray force” requirement in WaterSense.
GreenSpec lists showerheads that use no more than 1.75 gallons per minute (gpm)—below WaterSense’s limit of 2 gpm—and are WaterSense labeled to address spray force and coverage
Shower satisfaction is a complex and highly variable user experience, much like thermal comfort. Including the spray force and coverage criteria is a good start, but look for additional or improved engineering and metrics as this field matures.
WEc1: Water Use Reduction
WEc3: Water Use Reduction
WEc3.1-3.2: Water Use Reduction
WEp1: Water Use Reduction—20% Reduction
WEp1: Minimum Indoor Plumbing Fixture and Fitting Efficiency
WEp1: Water Use Reduction
Ratings and Commentary