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This article was originally published in the March/April 1999 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.

 

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Home Energy Magazine Online March/April 1999


trends
in energy

Miscellaneous Water Under the Energy Bridge

Pool pumps are one of several miscellaneous energy users that consume large amounts of electricity.
Table 1. Unit Energy Consumption Estimates for Water Bed Heaters, Well Pumps, and Pool Pumps
Product Type Low Unit Energy Consumption (kWh/yr) High Unit Energy Consumption (kWh/yr)
Water bed
Hard-side1
Soft-side2

1,100
0

1,400
490
Well pump3 100 140
Pool pump4 410 3,600
Notes:
1. These energy estimates are based on a standard water bed heater of 350 watts. The high estimate is based on data from Central Maine Power of an annual average duty cycle of 326 h/mo. The low estimate is based on a duty cycle of 254 h/mo. Both estimates assume a covered queen-size bed. The effects of room heating are not taken into account.

2. Energy estimated based on a water bed heater of 125 watts. The high estimate is based on data from from Central Maine Power of an annual average duty cycle of 326 h/mo. The low estimate assumes no heater. Both estimates assume a covered queen-size bed.

3. The low estimate is based on a 1/2 hp well pump rated at 650 watts, assuming full-load operation. The high estimate is based on a 3/4 hp well pump rated at 900 watts. (In some cases, the range of water pumped may be much lower or higher than these estimates, depending on the depth of the well, pump efficiencies, and usage patterns.) Usage in both estimates assumes a water requirement of 253 gal/day (for a household of four using 60-70gal/day) and a pumping rate of 10 gal/min.

4. The low estimate assumes a 3/4 hp pool pump (860 watts) operated 4 h/day, for 4 months. The high estimate assumes a grossly over-sized 2 hp pump (2,000 watts) operated 12 h/day for 5 months. The pump is assumed to be sized for a desired flow rate of 39 gpm.

Cover Your Losses

Ninety-five percent of the heat energy lost from a swimming pool is lost through evaporation, convection, and radiation to the atmosphere. Using a pool cover can reduce heat loss, and thus heating energy consumption, by half. The color of a pool cover determines how much solar radiation it gains and loses. Light-colored translucent covers allow solar energy to penetrate into the pool. Dark-colored covers cause the pool to absorb less solar energy during the day, which minimizes heat gain to the pool.

The material a pool cover is made of determines its convective and evaporative losses. A cover should, at minimum, be made of sheet vinyl attached to a foam insulating layer. The more expensive bubble-studded covers have air pockets in the material that reduce nighttime radiation loss while still capturing solar heat during the day. Another energy-saving heating strategy is to lower the thermostat setting for the pool. Each reduction of 1°F can cut energy consumption by 5%-10%. 

Small household appliances currently account for one-fifth of total U.S. residential electricity use, and comprise one of the fastest-growing areas of consumption--miscellaneous use. These appliances can be surprisingly large energy consumers; in some cases, one of them may be a household's largest individual user. When assessing energy use in a home, it is therefore essential to consider miscellaneous consumption. Appliances that fall into this category include such items as televisions, vacuum cleaners, coffee makers, and aquariums (see The Rage for Aquaria,HE Sept/Oct '97, p. 8). Water bed heaters, well pumps, and pool equipment are a few others.

Many energy conservation opportunities exist for miscellaneous electric products. Efforts like the U.S. Energy Star Electronics program are already capturing such opportunities for some appliances. Product types such as TVs, VCRs, and audio equipment do not consume large amounts of energy on the level of one household, but their overall use is important because so many people have them. Waterbed heaters, well pumps, and pool pumps, on the other hand, do consume large amounts of energy in individual households (see Table 1). Currently there are no programs for cutting energy use in these product types, although there are many ways to cut down on their use in houses. The amount of energy they use depends on the size and type of the products, how the products are maintained, and how consumers use them.

Water Beds Water bed energy consumption varies based on regional climate; consumer behavior (temperature settings and use of bedding); and bed characteristics, such as framing, depth, and insulation. Although the values listed in Table 1 are reasonable average estimates, water bed energy consumption can sometimes be much higher. For example, an uncovered king-size, hard-side (wood-framed) bed that is kept in a cool room can easily use more than 2,000 kWh per year. (See Saving the Other Energy in Homes, HE Nov/Dec '87, p. 13.)

There are several ways to reduce water bed energy consumption. One way is choosing the right kind of water bed to begin with. The newer heated soft-side models (with the same style as traditional mattresses) with perimeter insulation consume only one-third as much energy as the older-style hard-side models. For an average bed that consumes 1,1400 kWh per year, this can mean saving about 500 kWh per year.

The soft-side shallow-fill beds (with a depth of 4 inches) typically require no heater at all. Several midfill models (with a depth of 6 inches) do not require heaters, either. Beds that fall into this latter category include the Somma line and beds with convoluted foam insulation and thermal covers. With the exception of the Somma line, the deep-fill models (with a depth of 8 inches) do require heaters.

New alternative models are also being marketed. Strobel's Supple-pedic mattress is made out of Polyfilax, a fluid material that conforms to the shape of the body; its temperature sensitivity responds to body heat.

Assuming a heater is used and the thermostat is set to cycle throughout the day (this is standard practice), covering the bed each morning can cut energy consumption by one-half. This probably saves more energy that turning the heater on and off each day, because it takes so long and so much extra energy to return a cold bed to a comfortable temperature.

Well Pumps Well pump energy consumption varies based on pump size, household water use, pump operating pressure, and the depth of the water table. Proper maintenance and service of the well and plumbing saves both water and energy, and extends the lifetime of the well pump. Leaky faucets, showers, and hoses can increase demand on the pump by 2 to 3 gallons per minute.

Consistent well pump maintenance also ensures that the pressure tank is not waterlogged (filled with too much water). If the tank contains too much water, the pressure sensor that controls the pump is over-activated, causing the pump to work too long. Because the start-up phase of the pumping cycle requires the most energy, well pump energy consumption greatly increases. Furthermore, both system user leaks and waterlogging reduce the lifetime of the equipment.

Pump sizing should also not be ignored. Many 3/4 hp pumps are installed in wells that require only a 1/2 hp pump. Proper sizing can save the homeowner approximately $8 per year (100 kWh at 8¢/kWh), as well as saving the cost of the larger pump.

Pool Pumps Swimming pool pump energy consumption varies based on the volume and depth of the pool, the size of the pump, and the length of time the pump operates. Perhaps the easiest way to reduce pool pump energy consumption is to make certain that the pump is sized correctly and runs no longer than necessary (see Pool Bills Take a Dive, HE Mar/Apr '86, p. 35). The pump must be sized to match pool water flow rates and system friction losses. To size a pump properly, a pool specialist must consult design charts that match the hydraulic characteristics of the pump to the piping and flow characteristics of the pool.

Installing accurate timers to control the pumping cycle also saves energy. Reducing daily pumping time can save 150 kWh per year for each hour per day that pumping time is reduced; for inefficient pumps, the savings can be much higher. Because needed circulation time depends on usage, filter size, chemical treatments, scrubbing, and the rate of debris buildup, homeowners should be sure to check with a pool service provider or store to ensure adequate pumping.

As the amount of debris increases in a pool, more pumping is needed to keep the pool clean. The best way to prevent debris buildup is to circulate the water in a series of short cycles throughout the day rather than in one long period. Another way is to use a pool cover to keep the debris out. Covers also cut down on pool heating needs (see Cover Your Losses).

Recommendations Miscellaneous use is one of the fastest growing areas of residential energy consumption in the United States. Some of these frequently overlooked end uses can also account for a large percentage of household energy consumption. This is especially true if equipment is not maintained correctly or if occupant behavior increases energy use--a sudden unexplained spike in the utility bill could be caused by a malfunctioning well pump, or a pool pump with a broken timer, or an uncovered water bed in a cold room. Energy auditors and home performance specialists should keep these miscellaneous uses in mind when assessing a home's energy use.
--Marla Sanchez
Marla Sanchez is a researcher in the Washington, D.C. Project Office of Lawrence Berkeley National Laboratory.
 
 
 

 


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