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# how to covert WATTS/AMPS into \$\$

Member Posts: 2,398
Dave is about right, Gary but I have to adjust it just a bit. The formula only applies to single-phase power. (So my electrical engineer cohorts have always reminded me at great pain.)

Also, before you take nameplate Watts you may want to put an amp meter on the device first. The nameplate is a maximum draw and the actual circulator flow rate and head will likely differ. Likewise, voltage variances affect the amperage (they are interdependent as you know).

My Grundfos claims, from memory, 45 Watts on low speed but when corrected for voltage and amperage, drew about 35 Watts. Such a deal.

One of the great tools I enjoy is the "Kill-A-Watt" by P3. It is a plug-in appliance sub-meter but you can put a polarized plug on your circulator and do a sub-test.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

-Ernie White, my Dad

• Member Posts: 4,744
circs cost money

Hello,

can anyone tell me how to convert watts into dollars? I may be able to figure it out, but I know there's someone here who can do it faster than me.

lets say 80 watts and the cost of the power is .18 cents kw. Non stop circ; what's the fee for 30 days? It's the "time" factor that confuses me.

Thanks,

gary

Gary Wilson
Wilson Services, Inc
Northampton, MA
gary@wilsonph.com
• Member Posts: 299
\$10

80/1000 x 24 x 30 x .18
• Member Posts: 1,935
watt hours

if the 80 watt pump runs an hour, that 80 watt hours.

you buy kilowatt hours so thats .08 kilowatt hours per each hour the pump runs.

you can do the rest.....

so, you can run a 1,000 watt hairdryer 1 hr

or a 100 watt light bulb for 10 hours

or a 500 watt toaster for 2 hours

all add up to 1 kilowatt hour of power!
• OHMs Law

V X AMPS=Watts, basic high-school stuff, you do the math Gary.
1000 watts=1KW.

Dave
• Member Posts: 513
I'd like to insert my 2 cents

1 kw= 1000 watts

1kwh = 1kw X 1 hr

Divide your total bill...including all taxes, fees, whatever... what you write your check out for... by the number of kwh you're being charged for... to get your cost per kwh.
• Member Posts: 592
very good

Agree, but one small problem. Too many variations on utility bills, credit for this, charge for that, different rates for the first x hours of useage, than a different rate for the useage over that.

Would consider taking the average and trying to factor in somehow the marginal rate for extra useage.
• Member Posts: 299

"Also, before you take nameplate Watts you may want to put an amp meter on the device first. The nameplate is a maximum draw and the actual circulator flow rate and head will likely differ. Likewise, voltage variances affect the amperage (they are interdependent as you know)."

Would you bet your pinky ring on this?
• Member Posts: 299
That's what he did...

That's how he got his 18 cents.

BTW, including any fixed portions of the bill is WRONG for what he is doing! It simply won't affect his costs of running an 80 watt circ vs the 26-99 he has, if that's the reason for this analysis.
• Member Posts: 4,744
Thanks for all the answers

I'm good at looking stupid, a special talent I have.

I knew the watts/amps conversion, I just added "AMPS" so I wouldn't get all these tubing people wondering how to measure watts radiant; guess my clever idea backfired.

The conversion to electricity and KW/\$ makes perfect sense. Thanks to all.

Gary Wilson
Wilson Services, Inc
Northampton, MA
gary@wilsonph.com
• Member Posts: 513
I think you have

to include everything, if you want to know your cost.

It doesn't matter if you're paying for electricity, or fuel surcharges, taxes, or the new city hockey arena... the amount you write on your check divided by the kwh you use is your cost of electricity.

The ratio of the kw of the two motors will give you your comparison, without needing to know anything about the electric bill.

You can almost figure out a ratio of the cost from the nameplate amps and the power factor. Provided similar voltages and power factors, (KW = volts X amps X 1000 from which the effect of power factor has been multiplied out),a motor that draws 2 amps is going to cost you twice as much to run as one that draws 1 amp... but it might also pump more water...which would float a whole 'nother turd in the swimming pool.
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