Electrical costs for my pool

I finally went out and measured the amps on my control panel while turning the equipment on and off. Bottom line, the scheduled runtime of my filter, cleaner, chlorinator, and control panel itself at Houston's power rates is costing me $120/month. And I'm only running the pump for 8 hours. Add in the additional pump and waterfall pump time when people are swimming, and I'm up to about $160/month. Now I understand more why my bill went from $300 to $500 this summer. My builder said the electrical use would be about $30/month. Boy was he ever wrong... :mad: Attached is the spreadsheet with the numbers.

My pool is 20,000 gallons. My pump is overkill, so I'm wondering about the return on investment of going to a smaller pump. I'm also in the process of switching from Reliant to Dynowatt and my power costs should go from .168 to .135, or $166/month to $133/month.

http://home.houston.rr.com/poldervaa...the%20pool.xls

Robert

how did you measure the amps ? I think my pump costs around $200 a month in the summer to run but I don't know for sure. We pay 31 cents a KWhr.

thanks,
-- john

I bought a clamp on type of amp meter. You can measure volts in parallel by just putting the two probes of a meter on the contacts. But for amps and an older amp meter, you have to measure amps in series. In other words, take one wire off and put your meter in series with the ciruit. Along came the clamp on meters and you just put the clamp around the wire (either leg of 220 or the hot or neutral of 110) and it will tell you the amps. You can spend $100 or more on a multi-function meter with a clamp on amp meter, or since I already had an expensive mutli-meter without clamp on amps, I happened to find a single function clamp on amp meter for about $40. I'll get the make and model number tonight from home.

Robert

Now THATS impressive. I too want to know how you determined amps and volts.

Donnie

(BTW.......I stole a copy of your spreadsheet)

OOP's too slow.

I would think your payback on a smaller or two-speed pump would be very quick.

With a simple amp meter, you are neglecting the power factor. This is caused by amps getting out of phase with the voltage. Typically, power factors for motors are about 90% so you can subtract about 10% off of that bill.

The most accurate way to measure your power is to use the electric meter on the side of your house since that is what the power company uses. Each meter is a bit different but a call to your electric service or web site will show you how to convert to kwh.

If you know the amp rating of a particular motor, can you calculate the cost just from that?

What's the forumula you'd use?

I have a 12 amp motor, run it 24/7, and looking at my last bill I pay $.083 per KWH.

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Originally Posted by Rangeball

If you know the amp rating of a particular motor, can you calculate the cost just from that?

What's the forumula you'd use?

I have a 12 amp motor, run it 24/7, and looking at my last bill I pay $.083 per KWH.

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KWH is approximately (Amps X Volts divided by 1000) X Hours. At max current, your motor would use 12AX120V=1440W Dividing by 1000 gives 1.44KW X 24Hours= 34.56KWH per day, so at $0.083 per KWH, you are using $2.86 worth of electricity a day, or roughly $86 per month. Double that if that is a 220 motor.

The plate current is max, and you probably aren't using that. The only way to know how much current you are using is to measure it.

thanks for 220 then do I add the 2 legs together to get the total amps ?

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Originally Posted by JohnInSoCal

thanks for 220 then do I add the 2 legs together to get the total amps ?

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No, just one.

Quote:

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Originally Posted by JohnT

KWH is approximately (Amps X Volts divided by 1000) X Hours. At max current, your motor would use 12AX120V=1440W Dividing by 1000 gives 1.44KW X 24Hours= 34.56KWH per day, so at $0.083 per KWH, you are using $2.86 worth of electricity a day, or roughly $86 per month. Double that if that is a 220 motor.

The plate current is max, and you probably aren't using that. The only way to know how much current you are using is to measure it.

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For the same HP motor operating at 230v, it will use half the amps as 115v so the total power is the same.

JohnT, you would not have to double the cost for a 220 volt motor, as a 220 volt would use about half the amps. Therefore the cost would be approximately the same regardless of 120 or 220 volt motor.

Cheers

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Originally Posted by hancop

JohnT, you would not have to double the cost for a 220 volt motor, as a 220 volt would use about half the amps. Therefore the cost would be approximately the same regardless of 120 or 220 volt motor.

Cheers

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I was referring to the question that only gave amps and didn't mention whether it was 120 or 220. You are correct, but at a given current, 220 would essentially be double the power.

Quote:

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Originally Posted by JohnT

KWH is approximately (Amps X Volts divided by 1000) X Hours. At max current, your motor would use 12AX120V=1440W Dividing by 1000 gives 1.44KW X 24Hours= 34.56KWH per day, so at $0.083 per KWH, you are using $2.86 worth of electricity a day, or roughly $86 per month. Double that if that is a 220 motor.

The plate current is max, and you probably aren't using that. The only way to know how much current you are using is to measure it.

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Thanks.

I was always under the impression that I was spending around $35 per month. This makes 12 hour run time look much more attractive.

If you decide to use your house electric meter, here is a formula you can use:

kwh = 3.6 * Kh * R / T

Kh is the meter constant and usually printed on the meter. Most are 7.2.
R is the number revolutions you are timing. I use 10 when the pump is on and 1 when it is off.
T is the time in seconds for R revolutions.

If you measure with the pump off and then on and subtract the two, you get a pretty accurate number for just the pump.

my electric meter gives the reading for KWhrs but I have so much stuff going on generally it wouldn't be very practical to try and shut everything down and monitor the pool pump or AC. Currently we are using about 100 KWhrs a day, my last electric bill was $811 a personal record :)

Based on the estimated cost arrived at above, my pump accounts for 34% of my electric bill.

Timer here we come :)

Wow. Glad I posted a popular topic. I wasn't aware of the Power Factor. And it sounds like I need to do some more research on calculating motor costs.

I've found several articles on the web to read, but alas, my work is calling me... In addition to the PF number, there also seems to be a .00173 number that is also being thrown in. This was used to calculate kVA. Siting from http://www.cop.com/SEUhtmDOCS/SEU17.htm, the formulas are:
kVA = 0.00173 * V * amps
kw = kVA * PF * .01 (PF being % between 1-100)
running for one hour would be kwh and then multiply by number of hours times cost per kwh.

Now, looking at the calculations above and the linked site, they are using the stated amps on the nameplate, where I am using the measured amps on my amp meter. It looks like the only place they're using the measured amps is to help calculate the PF.

So what is the 0.00173 number? If I throw in the .00173 number and a 90% power factor, I'm actually increasing my kwh because the .00173 increases more than the .9 decreases it.

Robert

Just FYI at 60 GPM on my Intelliflo I run 1445 watts per hr. and it takes approx 11 hours to turn the pool over 1 time per day. If I drop it down to 40 GPM then I use 440 watts. The problem is the Trio Pure needs 55 GPM to work well.
No Bragging just sharing some options, the big issue is the $1250.00 price tag for the pump.

Does the intelliflow give you the watts or are you measuring it somehow?

Thanks,
Robert

Quote:

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Originally Posted by JohnInSoCal

my electric meter gives the reading for KWhrs but I have so much stuff going on generally it wouldn't be very practical to try and shut everything down and monitor the pool pump or AC. Currently we are using about 100 KWhrs a day, my last electric bill was $811 a personal record :)

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Thats why you measure it with the pump on and then off and take the difference. That way it does not matter how much stuff you have on.

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Originally Posted by rpoldervaart

Wow. Glad I posted a popular topic. I wasn't aware of the Power Factor. And it sounds like I need to do some more research on calculating motor costs.

I've found several articles on the web to read, but alas, my work is calling me... In addition to the PF number, there also seems to be a .00173 number that is also being thrown in. This was used to calculate kVA. Siting from http://www.cop.com/SEUhtmDOCS/SEU17.htm, the formulas are:
kVA = 0.00173 * V * amps

This is for a 3 phase motor. Standard motors are kVA = 0.001 * V * amps

kw = kVA * PF * .01 (PF being % between 1-100)
running for one hour would be kwh and then multiply by number of hours times cost per kwh.

Now, looking at the calculations above and the linked site, they are using the stated amps on the nameplate, where I am using the measured amps on my amp meter. It looks like the only place they're using the measured amps is to help calculate the PF.

So what is the 0.00173 number? If I throw in the .00173 number and a 90% power factor, I'm actually increasing my kwh because the .00173 increases more than the .9 decreases it.

Robert

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See comment above.

Also, to make it simple, kwh = Volts * Amps / 1000 * (PF%/100)

As others have said, the best way is to use the house electric meter. You don't have to turn everything else off, just make sure it stays constant when you run the test. You might want to unplug your refridgerator, as you cannot control when it will cycle. The power factor can vary alot. I have an old fridge that has a power factor of about 0.6 rather than the 0.9 mentioned.

Volts times amps only works for DC not for AC.

>just make sure it stays constant when you run the test

Yes, that is my issue. I have 5 refridgerators of varying sizes, some compact, under counter, etc. 2 AC units, freezer in the garage etc. I would need to shut them all down. And then monitor the usage over some time like a half hour correct and see what the difference is in KWhr ? My electric meter has a little wheel that spins like crazy, then 5 dials that directly show the KWhr used. If I monitor that over a half hour or hours time it could tell me the difference roughly as it's hard to tell half dial increments, etc.

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Originally Posted by cleancloths

As others have said, the best way is to use the house electric meter. You don't have to turn everything else off, just make sure it stays constant when you run the test. You might want to unplug your refridgerator, as you cannot control when it will cycle. The power factor can vary alot. I have an old fridge that has a power factor of about 0.6 rather than the 0.9 mentioned.

Volts times amps only works for DC not for AC.

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While that is technically true for motors, most other devices (e.g. light bulbs, electronic equipment, etc) watts = volts * amps AC or DC. The exact formula for AC is RMS Watts = RMS Volts * RMS Amps * Cosine (theta) where theta is the power factor angle and cosine (theta) is the power factor. For most circuits, theta is 0 so yes watts = volts * amps. However, for most motors, theta is small and the power factor about 90%.

Quote:

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Originally Posted by JohnInSoCal

>just make sure it stays constant when you run the test

Yes, that is my issue. I have 5 refridgerators of varying sizes, some compact, under counter, etc. 2 AC units, freezer in the garage etc. I would need to shut them all down. And then monitor the usage over some time like a half hour correct and see what the difference is in KWhr ? My electric meter has a little wheel that spins like crazy, then 5 dials that directly show the KWhr used. If I monitor that over a half hour or hours time it could tell me the difference roughly as it's hard to tell half dial increments, etc.

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If you use the horizontal wheel that spins very quickly as I suggested in my earlier post, you should not need to run the test more than five minutes. The pump uses enough power probably to give you 10 rotations in less than 2 miniutes. Without the pump, the rotations are so slow that one rotation should suffice. Time with and without the pump and use the formula I posted earlier. It is very easy to do. The other dials are not fine enough resolution to use effectively in a short period of time.

OK. So I've added Power Factor to my spreadsheet as a changeable parameter. This is probably pretty close, and I'll try to get out and count the meter spins to verify soon.

http://home.houston.rr.com/poldervaa...the%20pool.xls

Thanks,
Robert

The Intelliflo provides actual flow and watts consumed data to produce that flow . So if you have a restrictive system the flow per watt is lower. If I could figure out a way to have enough back pressure to run the Trio Pure and cleaner and keep the flow low I could clean my pool on 440 watts hr x 14 hrs a day. or 6.1 total amps a day.

The cool aspect is the pump will calculate the optimal flow per # of turn over per day for you if you do not use preset flow rates.