The case for pool pump upgrades

by Sally Bouorm | February 1, 2012 8:14 am

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By Steve Easley and Jeff Farlow

When people talk about home energy efficiency, the conversation seldom leads to pool pumps and that needs to change. One of the most significant energy-consuming devices in homes with swimming pools is the pool pump. Pumps keep pools clean and safe by circulating water through filters. They often also circulate water through heaters, cleaners, water features or fountains. Depending on the pool, some use one pump to perform all these jobs, while others use multiple pumps. Traditional pumps typically have one- or two-horsepower motors that run at least five to six hours per day, sometimes around the clock, consuming energy.

Understanding electrical consumption

The average swimming pool pump draws approximately 1,500 to 2,500 watts. If the pump runs 4.5 to six hours each day, it can add up to 10.5 kilowatt hours (kWh) per day or approximately 1,400 kWh per year—considering the average swimming season in Canada occurs between May and September. If the pump runs all day, as is common practice in many regions, these numbers can be significantly higher.

If the homeowner also operates a pool cleaner equipped with a booster pump, it can add another 1,200 to 1,500 watts. If the cleaner operates roughly 3.5 hours per day, the total combined consumption for these two pumps could exceed 2,500 kWh per year. Electricity rates vary by region, season, time of use and total consumption. For example, the on-peak summer rate in Ontario is 10.8 cents/kWh; using the numbers above, it would cost approximately $300 to operate the pool over a four to four-and-a-half month period. Loads like this can have a dramatic impact on both the electrical grid and pool owners’ wallets. In addition, pools typically run during electric utility peak load times, further straining the electrical grid.

One way to reduce this load is to replace older, single-speed pool pumps with a high-efficient, variable-speed pump with electronic controls. A traditional single-speed pump has an induction motor with typical efficiencies of 35 to 70 per cent. By comparison, variable-speed pump motors can achieve efficiencies above 90 per cent. The special permanent magnet synchronous motors (PMSMs) used in ultra-high efficiency pumps is similar to the motors used in hybrid cars. They can vary their speed, generating only as much flow as is required for each application.

High vs. low flow

In the swimming pool environment, high flow is required for some water features, pool cleaner cycles and spa jets. High flow, however, is not required for routine filtration, the mode in which a pool pump operates most. In fact, low flow helps pool filters operate more effectively. When a traditional single-speed pump is performing all those varied tasks, it has no choice but to run at high speed, effectively producing more flow (and consuming more energy) than is needed for simple filtration cycles.

A variable-speed pump running at a low speed will draw between 120 and 400 watts and consume, on average, about 2 kWh per day. By comparison, a single-speed (high only) pool pump consumes approximately 10 to 12 kWh per day. A variable-speed pump uses very little energy for low-speed/low-flow tasks like filtration. Therefore, it is possible, depending on energy rates, to spend 10 cents filtering a particular amount of water, while it would cost a full dollar to filter the same amount of water using a standard pump.

The role of physics

Some of these savings are a result of motor efficiency; however, another significant factor is that power consumption drops at a nonlinear rate as pump (motor) speed and water flow is reduced. In fact, when motor speed and flow rate is reduced by half, the power demand is reduced to 1/8 of the original power, at least in a laboratory setting.

Actual results in the field vary but often are around 1/7. Also, with less flow, the pump needs to run longer to achieve the same turnover for filtration purposes. As a result, the energy consumed will not be 1/8 when using half the flow, but can easily be 1/4. This is because the pump needs to run twice as long while consuming 1/8 of the power (i.e. 1/8 x 2 = ¼).

In other words, by running the pump slower, even though it will be operating longer, the lower speed translates into dramatic savings in energy consumption and operating costs. Plus, variable-speed pumps have higher quality motors—not only are they remarkably quiet, they also last longer, putting less strain on the filter, plumbing and other parts of the system.

When determining the ideal run time for the filtration system, it is important to make sure sanitizer levels are monitored and maintained and that water clarity is acceptable.

California case study

In October 2010, the upgrades described here were completed on a residential swimming pool in California in an attempt to reduce one pool’s energy consumption and its owner’s electricity bill.

California has a tiered electric utility rate structure, so the more kilowatt-hours used, the more a customer pays. It ranges from 12 to 40 cents per kWh, and swimming pools almost always correlate to the higher rate. Before the upgrades it cost $2,100 US per year to run the filtration, cleaner, light and solar heater on this 75,700-L (20,000-gal) pool. A separate waterfall pump also consumed energy, but was rarely used because it was loud and inefficient.

Before upgrades

• 1.5-horsepower (hp) standard pool pump (for filtration and solar heating);
• sweep-style pool cleaner with a ¾ hp booster pump;
• 2-hp waterfall pump; and
• 500-watt incandescent light

The original single-speed pump ran an average of six hours per day during the summer months, drawing about 2,100 watts for filtration and heating. The pool cleaner’s booster pump, which ran approximately 2.5 hours per day, drew an additional 1,400 watts. Combined, these two pumps were using an average of 16 kWh per day.

After upgrades

• variable-speed pump (for filtration, solar heating and pool cleaner);
• additional variable-speed pump for waterfall; and
• light-emitting diode (LED) lighting.

Filter pump upgrade

The main variable-speed pump draws 221 watts during the low-flow filtration cycle and 650 watts when it speeds up to operate the pool cleaner.

Filter pump operating cost comparison
Function	Old pumps		New variable-speed pump
	Summer	Winter	Summer	Winter
Filtration	· 2,092 watts	·  2,092 watts	· 221 watts	· 221 watts
	· six hours per day	·  four hours per day	· six hours per day	· three hours per day
	· 12.6 kWh	·  8.4 kWh	· 1.3 kWh	· 0.66 kWh
	· $153 per month	·  $102 per month	· $16 per month	· $8 per month
Cleaner	(Year round)		(Year round)
	· 1,372 watts		· 650 watts
	· 2.5 hours per day		· three hours per day
	· 3.4 kWh		· 2 kWh
	· $42 per month		· $24 per month

The cleaner’s booster pump used the same amount of energy year-round (3.4 kWh per day). When combined with the standard pool pump used for filtration and solar heating, this pool was consuming 16 kWh per day in the summer. The new variable-speed pump needs only 1.3 kWh per day for filtration and an additional 2 kWh for cleaning (as shown above). Total energy consumption after the retrofit was 3.3 kWh per day. During summer use, the upgrade makes a difference of 12.7 kWh per day (i.e. 16 – 3.3 = 12.7) in pump energy savings.

Waterfall pump upgrade

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A single-speed waterfall pump was also replaced with a variable-speed pump. The old waterfall pump was so loud it was difficult to talk over, and as there was no way to change the waterfall’s volume of water or sound, it was rarely used. Further, it cost almost $1 per hour to run.

With a variable-speed pump running the waterfall, its look and sound are now adjustable. Even at higher speeds the pump is exceptionally quiet—resulting in a more pleasurable experience at a far lower energy cost. Best of all, it uses approximately 900 watts on its high setting, and less than 200 watts on its lower setting, in comparison to more than 2,400 watts when using the single-speed pump.

Waterfall pump operating cost comparison
Old single-speed pump	New variable-speed pump
·  2,418 watts / $0.97 per hour	·  905 watts (high flow / $0.36 per hour)
	·  351 watts (medium flow / $0.14 per hour)
	·  187 watts (low flow / $0.07 per hour)

The pool’s lighting was also upgraded from halogen to LED, yielding additional savings. The net savings from changing the pumps and lights is about $125 US per month. The annual cost to run the pool is now $430, representing a savings of $1,670 per year. In addition, the filter is performing better and more efficiently due to slower flow. As a result, the pool water is cleaner, the water clarity has improved and the appropriate sanitizer levels are maintained.

Conclusions

There are several ways to reduce the energy consumed by swimming pools. Variable-speed pumps, however, top the list in terms of how much can be saved. Studies show these pumps can reduce a pool’s energy consumption by up to 90 per cent, depending on how often the pump runs, what it is used for (e.g. water features, circulation, running a pool cleaner, etc.) and the overall hydraulic design of the pool. The result is a 20- to 40-per cent reduction of the homeowner’s total monthly electric bill.

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A growing number of utility companies have discovered the advantages of high-efficiency multi-speed and variable-speed pumps, as they reduce energy use and provide significant reductions in peak demand.

To put all of this in an even broader context, it is interesting to note that retro-fitting existing homes for improved energy efficiency is increasingly viewed as a cornerstone of policy initiatives targeting clean energy development, according to the Home Performance Resource Center[4]. Practitioners of energy efficiency methods are also increasingly aware that swimming pools represent a large percentage of a home’s energy costs.

In addition to the significant energy savings that can be realized by using multi-speed and variable-speed pool pumps, an increasing number of professionals, in many energy-related fields, are also looking at LED lighting, energy-friendly heating methods and automation controls as ways to reduce the carbon footprint of today’s swimming pools.

 

 

 

Steve Easley is owner of Steve Easley & Associates in Danville, Calif., a nationally recognized building science consultant specializing in green and best practice building. He can be reached via e-mail at steve@steveeasley.com[5].

 

 

 

Jeff Farlow is program manager of energy initiatives at Pentair Water Pool and Spa. He is a nationally recognized expert on pool energy efficiency and is a member of the Association of Pool and Spa Professionals (APSP) committee dedicated to developing a standard for energy efficiency for residential inground swimming pools and spas (APSP-15). Farlow is also a member of the Canadian Standards Association’s (CSA’s) energy committee working on CSA-C840 performance of pool pumps. He can be reached via e-mail at jeff.farlow@pentairwater.com[6].

Source URL: https://www.poolspamarketing.com/trade/the-case-for-pool-pump-upgrades/

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