This article was originally published in the July/August 1994 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online July/August 1994
Low-Flow Showerheads, Family Strife, and Cold Feet
This article, which initially appeared in 1985, is another installment in Home Energy's Tenth Anniversary series. Its conclusion--that energy savings from showerhead retrofits can sometimes be less than predicted--was just slightly ahead of its time.
It is a documented fact that low-flow showerheads generally save less energy than a simple change in flow calculation would indicate. Home Energy is as guilty as others of blithely assuming that a reduced flow translates directly into energy savings. The problem is our faith in laboratory measurements that are performed without confirming field studies. One must remember that people use showers, not buckets and stopwatches. We outline below two reasonable situations where energy savings will be less than predicted by simple calculations. Auditors must recognize these situations and make adjustments in their energy savings estimates.
First of all, Americans no longer use their showers only to get clean. We can see small clues to this behavior in the gadgets being developed for the bathroom. For example, there are shower radios, shower clocks, shower mirrors, and, of course, easily accessible telephones. Wet shavers have appeared as yet another excuse to dawdle in the shower. A few people simply enjoy showers; indeed, this editor gets his best ideas in the shower. Given these distractions and entertainments, many people remain in the shower until they run out of hot water. In other cases, several showers in a row deplete the hot water tank. Then there is the notorious teenager who causes family strife by using all the hot water before a parent gets his or her turn.
Shower time can be extended by increasing the hot water capacity or reducing shower flow. Hot water capacity can be increased somewhat by raising the water heater temperature setting. The desired shower temperature will require less hot water mixed with cold, thus extending shower time. However, this option always increases energy consumption, so an auditor will not typically recommend this measure.
A low-flow showerhead is another strategy to increase showering time. The auditor may unwittingly recommend installation of low-flow showerheads in houses where in fact it will merely extend shower time or permit more family members to shower before that ominous temperature drop occurs. Clearly, installing a low-flow showerhead simply to increase immersion time does not save energy; instead the household obtains a new benefit. Researchers describe this effect as converting energy savings into increased amenity. In the worst case, all of the savings are converted to increased amenity. There will be NO energy savings, if, after installing a low-flow showerhead, the user (or users) continue to drain the hot water tank. On the other hand, some users will extend their immersion time only a few minutes. In this case, only a part of the saved energy is converted into increased amenity.
Probably only a small fraction of shower use falls into the above categories, but so little research has been conducted in this area that we can only speculate. A Southern California Gas Company survey of 500 homes, for example, indicated the average shower length was 7.5 minutes. Unfortunately, they neglected to ask: Do you shower until you run out of hot water? Some households, especially apartments, have small water heaters where even an eight-minute shower can drain the tank. (The arithmetic is simple: three gallons per minute of hot water should drain a 30-gallon tank in ten minutes, but cold water mixing and stratification reduce the effective capacity to under 25 gallons, or eight minutes of showering time.)
The cold feet syndrome is the second reason why simple flow calculations tend to overestimate energy savings from low-flow showerheads. A common complaint from very low-flow showers is that the water is cold by the time it reaches the feet. The user compensates by raising the temperature of the shower water. Actually, the problem begins earlier. Aeration is often used in the low-flow showerheads to give them extra body, but it results in rapidly declining temperature between the time the water leaves the showerhead and hits the naked body. (Aeration is in fact the principle behind power plant cooling towers and evaporative coolers.) Without knowing it, many users raise the temperature of the water 1deg.F to 10deg.F to maintain the same impact temperature. Our friends at Consumer Reports carefully measured the flow and comfort levels of thirty-three energy saving showerheads but failed to note this effect. Other reports have alluded to the cold feet syndrome, but have not recognized it as a small scandal.
The simple calculation of energy savings based on the difference in the flows of the old and new showerheads fails when the shower temperature also changes. Adjusting for increased temperature could reduce savings by as much as 20%. It is not difficult to include an adjustment for this phenomenon, but do you know anybody who does?
Low-flow showerheads save energy and should be installed. But sometimes there are unexpected complications. Family strife and cold feet are just two examples.
-- Alan Meier
Related ArticlesBig Flush, The: Saving Water in the Big Apple (Anderson)
Everything I Know about Energy-Efficient Showerheads I Learned in the Field (Warwick and Hickman)
Graywater: An Option For Household Water Reuse (Bennett)
Pulling Utilities Together: Water-Energy Partnerships (Jones, Dyer, and Obst)
Remodeling Bathrooms: Let the Energy Savings Flow (Johnston)
The Rise of Water Service Companies (Berlin)
Savings and Showers: It's All in the Head (Proctor, Gavelis, and Miller)
Xeriscape: Winning the Turf War Over Water (Iwata)
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