Image Credit: Ollie Crafoord
More Musings of an Energy Nerd
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.…
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18 Comments
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.
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.
Response to Jan Juran
Jan,
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.
Response to Tom Barrett
Tom,
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.
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.
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?
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.
Response to John Jacob
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
http://shop.solardirect.com/product_info.php?products_id=167
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.
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.
John
Response to John Jacob
John,
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:
http://www.solar-electric.com/sodcwapu.html
http://www.backwoodssolar.com/catalog/pumps.htm
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?
Response to Joe Boldt
Joe,
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).
Solar pool pumps - Response to Martin
Martin,
I have found my notes and provide the link here http://www.lorentz.de/en/products/solar-pool-pumps.html These systems offer direct solar connections with AC connection options as well.
Reponse to John Jacob
John,
Thanks for posting the link.
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!
RS485 ?
Does anyone have any info on controlling these pumps through the RS485 interface?
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.
RS485 control
I just started research on pool pumps, and while looking in the manual for this product - http://www.hayward-pool.com/shop/en/pools/res-pumps/tristar-vs-i-pmtrvs--1 - 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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