Electricity costs for my pool pump

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randytsuch

LifeTime Supporter
Mar 29, 2008
519
Los Angeles, Ca
I was thinking about getting a two/variable speed pump, to save energy costs, but then wondered how much I would save.
I saw some things on the net, including the pentair pool site, that claim considerable savings.

I started out trying to measure the current my pump was using (I borrowed a current probe from work), but the results I got did not make sense.

So, I measured at my electricity meter. There is a spinning thing on my meter, that makes one revolution per watt. I timed how many watts were used in about one minute, with the pump on and off. Did it three times

These are the worst (most expensive) set of results. Best case was $104 per year
0.238970588 watts/sec pump on
0.155979203 watts/sec pump off
0.082991385 delta (pump) watts/sec
4.979483128 watts/min
298.7689877 watts/hr
2.390151901 kwatts for 8 hr day
2.987689877 kwatts for 10 hr day
0.255403587 $ per 8 hr day
0.319254484 $ per 10 hr day
116.5278866 annual cost for 10 hr days

This is for a 1.5 hp pump, that has a service factor of 1.5. I think the pump is larger than it needs to be, my pool was built with an infloor cleaning system, but it no longer works. I think the pump was sized for the cleaning system. I had started to look into it, and thought I could use a 3/4 or 1 hp pump.

But, based on these results, I can't justify changing my pump.

So, unless I messed up my calculations, a new pump is not in my future. I am surprised that the pump does not use more electricity than this. The 300 watts per hour it uses is less than 1/2 hp, since 1hp = 746 watts. So, I guess my 1.5 hp pump is not working that hard?

For the numbers above, I counted 13 watts in 54.5 seconds pump on, and 9 watts in 57.7 seconds pump off

I am lucky, my electricity cost is just under 11 cents per kwatt, so that helps.

Randy
 
I think you have your math slightly wrong. You are mixing up where time goes in the units. Revolutions count some multiple of watt hours, typically 7.2 though that varies. If we call the number of watt hours per revolution Kh and the delta time in seconds t, then the power used by the device in watts is 3600 * Kh / t.

1.5 HP pumps vary somewhat, but the number of watts should be somewhere around 2000 watts.
 
JasonLion said:
I think you have your math slightly wrong. You are mixing up where time goes in the units. Revolutions count some multiple of watt hours, typically 7.2 though that varies. If we call the number of watt hours per revolution Kh and the delta time in seconds t, then the power used by the device in watts is 3600 * Kh / t.

1.5 HP pumps vary somewhat, but the number of watts should be somewhere around 2000 watts.
Click to expand...

Hi Jason
Thanks for the advice on the meter.
It does say 7.2 on the meter, so I will assume you are right

My adjusted numbers are now
1.720588235 watt hours/sec pump on
1.12305026 watts hours/sec pump off
0.597537975 delta (pump) watts-hours/sec
35.85227852 watts hours/min
2151.136711 watts hours/hr
17.20909369 kwatts hours for 8 hr day
21.51136711 kwatts hours for 10 hr day
1.838905826 $ per 8 hr day
2.298632283 $ per 10 hr day
839.0007832 annual cost for 10 hr days

This is the worst case, it varied from $750 to this.
Either way, it's a big number.

I am surprised a 1.5 hp pump uses this much power though.
The 2151 watts converts to about 2.9 hp, so my pump is only 50% efficient?

My other measurements, 224 VRMS and 8.4 ARMS come out to 1882 watts, so the numbers correspond.

Guess I will be looking into pump options.
Thing is, I have not found data on how much energy the double speed/variable speed pumps use, to know how much I would actualy save

Randy
 
That looks much better.

50% efficiency is typical, there is some variation but pool pumps are always somewhere around there.

A two speed pump will draw about 1/3 as many watts on low speed as on high speed and move 1/2 as much water. A variable speed pump will draw somewhere between 100 and 500 watts, depending on just which speed you put it on and some of the details of your plumbing.
 
Depending where you are located (months per year of operation and electric costs) you might want to consider an Intelliflow pump. I just put one in and am very happy with it. I can run it 24/7 and have it consuming well under 300 watts.

Previously I had a 1.5hp Hayward Super II Pump that died last year. I normally like to run the pump at night, but last year ran it in the day at times as I had installed a couple of solar mats. Now I can run it just for the solar in the day and boost the output at night when power is cheaper.
 
kirbinster said:
Depending where you are located (months per year of operation and electric costs) you might want to consider an Intelliflow pump. I just put one in and am very happy with it. I can run it 24/7 and have it consuming well under 300 watts.

Previously I had a 1.5hp Hayward Super II Pump that died last year. I normally like to run the pump at night, but last year ran it in the day at times as I had installed a couple of solar mats. Now I can run it just for the solar in the day and boost the output at night when power is cheaper.
Click to expand...

I live in LA (just added it to my profile). We use the pool from around April to Oct, 7 months or so.
I recalucated my costs based on a 7 month season, running 8 hrs per day for 7 months, 4 hours/day the other 5 months. I have to pool covered, so I can get away with lower pump time when the pool is not is use.

Annual cost comes out to $500 with those hours.

Using 300 watts at 24/7 for a variable speed, I only am calculating a saving of around $50/yr over a 2 speed pump. If those numbers are right, it does not justify the $300 or so addtional for the variable speed pump.

And, I just backwashed this weekend, so I need to calculate again. My filter pressure was at 22, it is now at 15. I expect the new calculations to be lower, and I would take an average of the two.

Randy
 
Hi, Randy,

This tricked me when I first started with pools but, with a constant speed pump, the lower pressure will result in increased electricity consumption....albeit pretty small. Essentially, the pump pushes more water or "does more work" as a result of the lower pressure.

I'm not sure how that relates to a variable speed pump but I'm sure someone will be along soon to help me understand it a little better.
 
duraleigh said:
Hi, Randy,

This tricked me when I first started with pools but, with a constant speed pump, the lower pressure will result in increased electricity consumption....albeit pretty small. Essentially, the pump pushes more water or "does more work" as a result of the lower pressure.

I'm not sure how that relates to a variable speed pump but I'm sure someone will be along soon to help me understand it a little better.
Click to expand...

So, you mean I cleaned my filter to save money, and it will actually cost me more money?
But, if I had a variable speed pump, where I could adjust the flow, then after I backwash I could adjust it down, and really save money.

Randy
 
I have a variable speed pump. On filter mode I run 27 gpm. My filter was getting increasingly dirty so I cleaned it yesterday. Prior to cleaning I was running 350 watts. Now I'm running 165 watts. Dirty filter means more backpressure on the pump. So to run a given flowrate the pump will work harder. A constant speed pump will work less hard against higher pressure but move less water as well. Get a multi-speed or variable speed pump. You will save money if you set it up right. And only run it long enough to keep the water clean. I've come to realize my pool doesn't need a daily volume turnover to stay clean. One nice feature with the intelliflo pump is that you program how much water you want it to pump in a day and that's all it will do. So, I've continually adjusted my volume down. Right now I'm filtering half the pool volume daily and the water is crystal clear. Of course, no one is swimming yet! Just need a few more degrees.
 

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As you reduce the speed on a variable speed motor you move less water and use less electricity. The electrical usage falls more quickly than the water slows down so your efficiency increases. Essentially, at lower speeds you are reducing the friction loss in the pipes and so using a higher percentage of the electricity to actually move water.

At a fixed speed, when you increase the resistance to flow, say by allowing the filter to get dirty, you are reducing the amount of water that gets moved. There is also another, more complex thing going on. Each pump, at a given speed, has a "sweet spot" a resistance to flow at which the pump uses the least electricity. Either increasing or decreasing the resistance to flow away from this sweet spot will increase the amount of electricity used by the pump. The efficiency of the pump is changing. Depending on where your particular system works out to be on the pumps efficiency curve, increasing the resistance to flow may either increase or decrease the total amount of electricity being used, depending on if you are getting closer or further away from the sweet spot.

These two effects are more or less independent of each other. For the most part changing the speed doesn't change where you fall on the efficiency curve. The increase in efficiency with lower speed is the dominant effect. The change in efficiency with where you fall on the efficiency curve is usually a much smaller effect, except when you are very far from the sweet spot.

Increasing the resistance to flow always lowers the total flow at any given fixed pump speed. Usually that reduction in flow is larger than any improvement in efficiency you might get by moving closer to the sweet spot in pump efficiency. However, if you are far enough away from the sweet spot it is possible for the improvement in pump efficiency to be larger than the reduction in flow and for the total system efficiency to improve. Because of this, systems that have a particularly low resistance to flow can sometimes be improved by restricting the flow intentionally.
 
With my new pool build the PB is going to use a whisperflo 3/4 for our new 18x36 IG pool. I had suggested a variable speed pump but he said it would be a 1000.00 upgrade does this seem right? I too am looking for a more economical setup for the long haul. I just don't want to faint every month the electric bill comes. Any suggestions? I was also concerned since I'm going to have 4 water spray features as well to help cool pool.
 
The variable speed pump is more, but it doesn't need to be that much more. An IntelliFlo VS is perhaps $500 more at deep discount Internet prices, while the IntelliFlo VF would be more like $900 more. If he was referring to the VF then $1000 more installed is very reasonable, but the VS should be less than that.

A variable speed pump costs more up front and uses less electricity. Depending on your electric rates that may or may not be worth it for you. The WhisperFlo should work just fine for your pool, it will just cost more to run.
 
whoozer said:
With my new pool build the PB is going to use a whisperflo 3/4 for our new 18x36 IG pool. I had suggested a variable speed pump but he said it would be a 1000.00 upgrade does this seem right? I too am looking for a more economical setup for the long haul. I just don't want to faint every month the electric bill comes. Any suggestions? I was also concerned since I'm going to have 4 water spray features as well to help cool pool.
Click to expand...

A variable speed pump would be like an Intelliflo, which is probably close to $1000 more than the Whisperflo. A two-speed pump would probably only be a couple of hundred dollars more.
 
HarryH3 said:
Ouch! I didn't realize that the variable speed pumps cost so much more. I guess the real question is: Will the pump actually last long enough to recover the additional up front cost?
Click to expand...

That's why I am doing this, to see if it makes sense.

More numbers
after backwash, filter pressure = 15
2029 watts/hr (average of two readings)

Before backwash, filter pressure = 22
1965 watts/hr (average of two readings, I threw out one reading because it was way higher than the other two)

New annual cost of $493 per year, running 8 hrs per day for 7 months, 4 hrs/day for 5 months.

I can get a whisperflo 2 speed pump for around $550 with tax, or a intelliflo 4 speed vs3050 for $870 with tax.
LA DWP has a $300 rebate for buying either one of these pumps. I also guessed at an installation cost of $200.

Based on my present pump numbers above, with a 2 speed saving 33%, and the 4 speed running at 300 watts for 2.5 times the current run time. My cost for electricity is cheap at 12 cents/kilowatt
At 8 hrs run time per day, two speed has a 2.8 year break even point, and the vs has a 3 year break even.
At 6 hrs run time per day, two speed has a 3.7 year break even point, and the vs has a 4.2 year break even.

Even though the vs3050 has a longer break even point, I am leaning towards it, as it will save money over the long run, and will be easier to install. I can wire up the VS3050 same as my present pump, just 220V input. The two speed would take another set of wires, not a big deal since I just installed a 3 device timer which can controll a 2 speed pump.

The LA DWP rebate program said for the Ikeric, Hayward Tri-Star adn Pentair VF pumps, you need a controller capable of automatically switching speeds to be eligible for the rebate, so that pretty much disqualifies these pumps for me. The additional premium for the VF, along with no $300 rebate would make the break even point too long.

Randy
 
randytsuch said:
The LA DWP rebate program said for the Ikeric, Hayward Tri-Star adn Pentair VF pumps, you need a controller capable of automatically switching speeds to be eligible for the rebate, so that pretty much disqualifies these pumps for me. The additional premium for the VF, along with no $300 rebate would make the break even point too long.

Randy
Click to expand...

Not certain about DWP, but SoCal Edison has an exemption for the VF. That pump does not require a controller, because it has built-in timer functions. Check to see if DWP has a similar exemption.
 
Well right now I'm paying 11cents but it is supposed to go up at some point this year. I believe he said the 30/50 was 1000more. I'll have to check again. What is the huge difference workwise between the vs and Vf? variable speed variable flow :scratch: sorry I'm so clueless with his stuff :oops:
 
The pump and motor is exactly the same between the VS and VF... the difference is that the VF has electronics built in which let you set a FLOW rate (and some other cool tricks)... the pump then changes the RPM's on it's own to compensate for pressure changes. With the VS, you only have the ability to set the RPM's.
 
So with water features should I have a vf or will a vs be ok. Will I save in electricity over the 3/4 horse because of the compensation in speed? My pool is pretty basic other then the 4 water sprays/slide/swg. Is that enough to justify variable speed? As a woman knowing little about rpms etc and having a hubby that could care less I need guidance :lol: :lol:
 

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