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Musings of an Energy Nerd

Is Your Pool an Energy Hog?

Replacing your old single-speed swimming pool pump with an efficient variable-speed pump is an energy retrofit measure with a very fast payback

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Is your pool an energy hog? If your electricity bills are sky-high during pool season, your pool pump may be to blame. [Photo credit: Ollie Crafoord]
Image Credit: Ollie Crafoord
Is your pool an energy hog? If your electricity bills are sky-high during pool season, your pool pump may be to blame. [Photo credit: Ollie Crafoord]
Image Credit: Ollie Crafoord
The Pentair IntelliFlo is an efficient variable-speed pool pump.
Image Credit: Pentair

If your home has a swimming pool, your pool pump may use more electricity than any other appliance in your home — as much as three times the electricity used by your refrigerator. Many residential pools in the U.S. have 1.5-horsepower or 2-horsepower pumps that draw 2,000 watts or more. If you’re not paying attention, you may be running your pool pump for 24 hours a day — even though your pool might be perfectly clean with only 6 hours of pump operation per day.

If your pool has one of these older single-speed pumps, installing a new variable-speed pump is one of the most cost-effective energy-saving measures you can take.

You want a variable-speed pump

The main purpose of a pool pump is to circulate water from the swimming pool through a filter. In addition, a pool pump is sometimes used to circulate water through an artificial waterfall or other so-called “features.”

For years, pool installers have specified oversized single-speed pumps — a type of pump that is inexpensive to install but expensive to operate. Many swimming pool pumps perform multiple functions, and installers traditionally sized a pump that was big enough for the most demanding task — for example, circulating pool water through a heater, energizing spot jets, or vacuuming the pool. Most of the time, when the pump is merely circulating water though the filter, it’s oversized.

A two-speed pump or a variable-speed pump does a better job of matching the speed of the pump (and its watt draw) to the task being performed. Compared to a single-speed pump, a two-speed or variable-speed pump can save tremendous amounts of energy. According to one source, compared to a single-speed pump, a two-speed pump can yield 55% energy savings, while a variable-speed pump can yield 83% energy savings.

A useful document prepared by the U.S. Department of Energy, “Measure Guideline: Replacing Single-Speed Pool Pumps with Variable Speed Pumps for Energy Savings,” explains that variable-speed pumps are preferable to two-speed pumps. The document notes, “The two-speed pump uses an induction motor and is basically two motors in one with a standard 3,450 rpm (full-speed) motor and a 1,725 rpm (half-speed) option. Ideally these motors may enable significant energy savings for the homeowner; however, if the half-speed motor is unable to complete the required water circulation task, the larger motor will operate exclusively. Because there is are only two speed choices it is much more difficult to fine-tune the flow rates required for maximum energy savings.”

The most efficient type of swimming pool pump is a variable-speed pump. The document notes, “A variable-speed pool pump will allow the homeowner to achieve the ideal filtration flow rate with the least amount of energy consumption. Variable speed pumps utilize … permanent magnet motors (PMM). … PMM pumps can produce the same gpm flow rate as single-speed induction motors if needed; they simply run much more efficiently. … Variable speed pumps are noticeably quieter, require less maintenance, last longer, and, through slower water filtration rates, allow for better and more effective filtration of the pool water.”

Reducing pool pump energy consumption

Here’s a list of pool pump energy tips:

  • The best pump is a variable-speed pump. Two-speed pumps fall somewhere between variable-speed and single-speed pumps in performance. Single-speed pumps are the worst.
  • Choose the smallest possible pump; most residential pools requires a pump that is no larger than 3/4 horsepower.
  • All piping connected to the pool pump should be at least 2 inches in diameter. Pipe runs should avoid 90° elbows; instead, use long-sweep 90s or 45s.
  • Pool pumps should operate for as few hours a day as possible — ideally 6 hours or fewer. However, it’s better to have a small pump that runs for more hours per day rather than a powerful pump that runs for fewer hours per day.

The Pump Affinity Law

The advantage of a small pump is explained by the Pump Affinity Law, which states that the power consumed by a pump is proportional to the cube of the flow rate. This means, for example, that if a pump’s flow rate is reduced by half, its power draw is reduced to one eighth. If you reduce a pump’s speed from 3,450 rpm to 2,400 rpm — a 30% reduction in speed — the watt draw drops from 2,000 watts to only 593 watts — a 70% reduction in power.

If you reduce the speed of a pump motor by half, you get half the water flow, so you will have to operate the pump for twice as long as you would if you used a pump with a more powerful motor. But since the low-speed motor only draws one-eighth as much power as the high-speed motor, it will only require one-quarter as much energy (in theory; actual savings are somewhat less than theoretical savings) to move the water with a smaller pump.

Examples of savings

Replacing a typical 1.5-horsepower single-speed pool pump with an efficient variable-speed pump will result in energy savings of 50% to 75%, according to the Department of Energy. Actual savings may be even higher; savings depend in part on how many hours per day you have been running your pool pump.

There are many examples of homeowners who save between $800 and $1,100 a year by installing a new pump; in one case, a pump drawing 1,900 watts was replaced with a variable-speed pump that draws only 150 watts.

How much does a good pump cost?

If you hire a pool contractor to replace an old single-speed pump with a new variable-speed pump (which comes with a controller and programmable timer), expect to pay between $1,400 and $1,800 — significantly more than the cost to install a single-speed pump ($400 to $700) or a two-speed pump ($700 to $1,000). Of course, if you install the pump yourself, the cost will be less.

Although a variable-speed pump is expensive, the payback period for this work can be as short as one or two years. Moreover, many electric utilities and state governments offer rebates to offset some of the cost to install a variable-speed pool pump. These incentives range from $75 to $300 per pump, and are available to at least some customers in Arizona, California, Florida, Massachusetts, New York, Pennsylvania, Rhode Island, Texas, and Vermont. (This is an incomplete list of states with rebate programs; the programs are subject to change.)

For up-to-date information on pool pump rebate programs, visit the Database of State Incentives for Renewables and Efficiency (DSIRE) website.

It should be noted that at least three states — California, Arizona and Florida — have recently passed laws that ban the installation of old-fashioned single-speed pool pumps for residential swimming pools.

A new ANSI standard

Prodded by forward-thinking energy-efficiency advocates in California, Arizona, and Florida, the pool pump industry is (slowly) moving to develop and promote more efficient pumps.

The recent pool pump requirements passed by the Arizona and Florida legislatures both reference a relatively new ANSI standard, ANSI/APSP/ICC-15a, “American National Standard for Residential Swimming Pool and Spa Energy Efficiency.”

The ANSI standard is based on California’s Title 20 requirements (the California appliance standards) and Title 24 requirements (the California energy code). Pool pumps were first addressed by California Title 20 in 2006, and by California Title 24 in 2012.

How do I know what kind of pump to install?

Here are four pool pump models that are energy-efficient and that have variable-speed motors:

These pumps are listed as examples; the list is not exhaustive. Most electric utilities with rebate programs maintain an online list of approved pool pumps.

The Energy Star program now labels pool pumps

Another source of information on efficient pool pumps is the Energy Star program. To be eligible for an Energy Star label, a pool pump must have a minimum energy factor (EF) of 3.8. (Pool pump EF is the ratio of gallons of flow per hour divided by watt-hours, as measured by the ANSI/HI 1.6-2000 method.)

A list of pool pumps that meet the Energy Star specification has been posted online.

The Energy Star specification for pool pumps allows single-speed pumps to obtain an Energy Star label. So far, no pump manufacturer has been able to develop a single-speed pump that is efficient enough to meet the Energy Star standard, but it is possible that one may be developed in the future. If you are in the market for a variable-speed pump, check the specs before you make your purchase, since an Energy Star label may not be enough to steer you in the right direction.

Should HERS ratings reflect swimming pool energy use?

At this time, HERS ratings ignore energy used for swimming pools. Fortunately, the RESNET Technical Committee is working to amend the way HERS ratings are calculated so that pool energy use is accounted for.

Jeff Farlow is the program manager of energy initiatives at Pentair, a manufacturer of pool pumps. Among pool pump professionals, Farlow is a standout who clearly understands the need for energy-efficient pumps. According to Farlow, “RESNET is developing a HERS-type rating for swimming pool that will be based on ANSI/APSP 15. We’re also talking to BPI [the Building Performance Institute], as well as trying to educate home performance contractors. The Energy Upgrade California program for existing homes now has a component for swimming pools. I’m hearing from home performance contractors who say, ‘Please include swimming pools in any package of energy improvements,’ because a variable-speed pump is a low-cost item compared to other energy upgrades, and it has a payback period as short as one year.”

Martin Holladay’s previous blog: “Climate-Specific Air Conditioners.”

Click here to follow Martin Holladay on Twitter.


  1. Jan Juran | | #1

    Important Issue
    Hi Martin: you are correct to highlight this important issue. After purchasing my Southampton NY house, I benchmarked its electricity use and was surprised to discover the old single speed pool pump was the #1 electricity user. I swapped it for a new VS Pentair model and estimate my electricity savings at 75% with better functionality and much less noise. Variable speed allows me to program a slightly higher speed to pump the solar thermal pool heater panels, a lower filtration speed when bypassing the solar heater, etc. BTW the old single speed pool pumps are enormous contributors to grid congestion/overload, high electricity costs during peak summer demand hours, peak load grid instability, and utility rate increases (the cost of a KWHr purchased by a utility can be very high on a summer afternoon) even for ratepayers who do not have pools, in essentially all summertime peak load utility districts in the US. I corresponded with the Chief Exec of LI Power Authority to bring these issues to his attention a few years ago; Long Island now prohibits single speed pool pumps for new pools and LIPA now provides rebates for VS pump retrofits. I would urge anyone who is a ratepayer and customer of a summertime peak demand utility to write to their utility CEO to bring these issues to the utility management's attention, as a concerned customer. As Martin points out, the solution actually saves money for a pool/homeowner: a VS pool pump costs less than its electricity savings over a short payback period. Of course, the lower noise level and improved functionality is free.

  2. Tom Barrett | | #2

    Variable Speed Pool Pumps
    Great column. Variable speed pool pumps work like magic. In our Extreme Energy Makeover project for San Diego Gas & Electric a few years ago we retrofitted the homeowner's pool with a variable speed pump and new filter. The pump operated 8 hours a day for less than what the single speed pump operated for one hour. Another benefit was that it could not be heard, it was absolutely quiet. The same pump also has the capacity to operate a water fall, spa, and other water features if your pool system has them.

    A couple problems did surface before we could install the variable speed pump. 1) The plumbing was inadequate to handle the variable speed pump. The pool was installed in the mid 1970s and the variable speed pump would not operate properly with the way the pool plumbing was installed. Get that checked first. We ended up redoing all the pool plumbing to make it work. 2) The return pipe at the bottom of the pool was significantly blocked with construction debris from when the pool was built. Check out that too. It was no wonder why the homeowner had so many problems keeping the pool clean. The pool retrofit, without the variable speed pump, new filter, and controller cost $17,000 just to get the new pump to work properly.

    So while I highly recommend variable speed pumps, make sure they will work with your pool first. If installing a new pool specify this system up-front. It is well worth it.

  3. User avater GBA Editor
    Martin Holladay | | #3

    Response to Jan Juran
    You're right -- this is one of those energy upgrades that is a win / win / win move. A new pump is quieter, saves the homeowner money, reduces the utility's peak load.

  4. User avater GBA Editor
    Martin Holladay | | #4

    Response to Tom Barrett
    Thanks for the reminder that large-diameter piping with gentle elbow fittings and no clogs is essential to an efficient system. Another point worth mentioning: oversized filters work better than small filters.

  5. Curt Kinder | | #5

    Ditto Great Column
    Florida is overrun with pools - I tally their power usage on every energy audit - at least note operating hours and horsepower.

    One client we TED-metered her pool pump - wasn't all that big a pool. She ran 1 HP pump 4 hours per day. TED came up with 6.7 kwh / day, consistent with what we've learned about typical 1 HP nameplate pumps...~1600 Watts. We retrofitted a Pentair Intelliflo. We were able to use its lowest flow setting, 15 GPM and still get full circulation. I confirmed 3 ways that power use had dropped from ~1600 Watts to 115 Watts. We set daily hours up from 4 to 6.

    Result was that we chopped the "6" off the initial 6.7 daily kWH, dropped it to 0.7 kwh / day. Put another way, pool filtration went from a dollar per day to a dime per day.

    We achieved results nearly as good on another pool pump burning $100 / month...a 2 HP pump operated 12 hours per day.

    Reply about eliminating tight elbows is good. Taking the idea a bit further - if the pool has a sand filter, get rid of it - very high head loss, wasteful backwash. Also, the special valve that provides a backwash path is said to cause high head loss even in non-backwash mode.

    Word in my area is that the two speed pumps do save some energy, but they are shortlived and actually quite inefficient in the slow speed.

  6. John Jacob | | #6

    Solar pool pumps
    I have read that DC variable speed motors powered directly from solar panels are a good item to consider as they will remove 100% of the motors use from the electric bill.

    Do you have any information on these setups?

  7. Curt Kinder | | #7

    Sounds good in theory, but...
    Pool pumping requirements are often independent of available sunlight, so it would probably make more sense to keep the pump and any PV panels decoupled, and let the grid act as a battery, 'storing' excess and making up for deficiencies.

  8. User avater GBA Editor
    Martin Holladay | | #8

    Response to John Jacob
    I have such a pump on my own solar thermal system -- an El Sid pump from Ivan Labs (Jupiter, Florida).

    Here is a link to one retailer that carries the pump

    El Sid pumps are very good pumps -- efficient and dependable. Since the pump is directly powered by a small PV array, there is no need for a pump control.

    Needless to say, though, this is a small 3.5 watt pump. It isn't capable of circulating swimming pool water through a pool filter. It is intended to circulate water (or water and antifreeze) in a closed loop between a storage tank and one or two solar thermal collectors.

  9. John Jacob | | #9

    Solar pump
    Martin, thanks...I have seen full size pumps that are direct DC from small solar arrays, as powerful as "normal" pool pumps. They are independent of mains electricity and run when the sun shines, or not. Here in the tropics we have plenty of sun. I am told to plumb this in and keep the mains pumps plumbed as well in case of a period of prolonged sunlessness.

    The problem is I while I saw this at a solar expo I can not find them available for sale. Seeking suggestions.


  10. User avater GBA Editor
    Martin Holladay | | #10

    Response to John Jacob
    Most DC pumps that are wired directly to a PV array are submersible pumps that pump from a drilled well to an above-ground tank. I don't think such pumps make sense for a swimming pool, but it's possible that one might work.

    Here are some links:

  11. Joe Boldt | | #11

    Pond Pump
    I don't have a pool but I do have a pond (4,000-5,000 gallons). According to general guide lines for a pond with Koi, it needs to turn over once per hour, although with the large size of mine I can get by at about half that. The pump runs 24/7.

    Do you know if the rebates (I live in San Diego) would apply to this sort of usage?

  12. User avater GBA Editor
    Martin Holladay | | #12

    Response to Joe Boldt
    For details about a local pool pump incentive program, you'll have to contact your local utility in San Diego (or whichever agency is sponsoring the rebates in your area).

  13. John Jacob | | #13

    Solar pool pumps - Response to Martin

    I have found my notes and provide the link here These systems offer direct solar connections with AC connection options as well.

  14. User avater GBA Editor
    Martin Holladay | | #14

    Reponse to John Jacob
    Thanks for posting the link.

  15. Spydo Staxxe | | #15

    THis is a very helpful article
    I just went to a variable speed pump... I wish the link in this story to

    "American National Standard for Residential Swimming Pool and Spa Energy Efficiency."

    worked though!

  16. Spydo Staxxe | | #16

    RS485 ?
    Does anyone have any info on controlling these pumps through the RS485 interface?

  17. Spydo Staxxe | | #17

    Variable Speed pump costs
    You can do a lot better than the costs stated in this article.

    I bought my V-Green variable speed pump for $450 online, shipped. It cost me another $150 at the pump repair depot to have it installed on my wet end, and to change out the impeller with a larger one (since the new pump is higher HP).

    I brought it home, pulled the service disconnect, hooked up the 220V and earth ground, reconfigured my timer to run 24x7 (since the new motor has its OWN timer).

    Total cost, about $600. I'm qualified to do the install myself, but even if you need to hire an installer, his bill should only be $100 or less. It's a 15 minute job.

    I calculated (based on 8 hours average duty/ day) we were spending about $600/yr with the old pump. I plan to chart current vs spinspeed on the new pump, then I can caulculate the savings, but even if I only save 50% (a very low estimate) the new pump pays for itself in 2 years.

  18. Michael Elliot | | #18

    RS485 control
    I just started research on pool pumps, and while looking in the manual for this product - - i noticed that RS485 was mentioned as the interface with a control system from the same company. They even sell the pump for $50 less without a control panel to take advantage of this. Other manufacturers probably have something similar.

    Oh - i just re-read your question and i guess you are looking for the control end - unless you buy from the pump manufacturer, you will probably need to roll your own on some home automation product.

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