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Join Date: Aug 2008
Location: Nigeria, West Africa (+1 GMT)
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KWh calculation for utility power supply

10/16/2008 4:45 PM

Hi guys,

My approximate total load is 50A per phase and Iam on a 3 phase power supply. How can I estimate my consumption in terms of Kwh so that I can estimate my monthly utility bills. Lets say the kwh costs 50cents. I will appreciate your assistance.

Regards

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#1

Re: KWh calculation for utility power supply

10/16/2008 5:13 PM

Well, In general, for a balanced 3ph system- (which is not going to be entirely correct)

Power=(1.732)*(line voltage)*(line current)*(power factor)

But this will not be too accurate

Call your utility company and get the power consumption history for your address, this might be somewhat more realistic, and most likely a bit easier.

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#2

Re: KWh calculation for utility power supply

10/16/2008 9:18 PM

hehe, it seems less answer to this thread. I like to help those who come from africa.

its this,

measure your phase voltage at same time. then you will get.

phase boltage x 50 x 1.73 x 3600/1000 = * kwh.

* kwh x 50 cents x 30 (31) = * moth charge.

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#5
In reply to #2

Re: KWh calculation for utility power supply

10/17/2008 2:47 AM

haha, forget a 24 hours a day.

so * kwh x 24 x 50 x 30 = * monthcharge

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Guru

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#3

Re: KWh calculation for utility power supply

10/16/2008 11:44 PM

Power = sqrt(3) *V * I * Power factor

Take PF = approx 0.8 ( usaul standard unless You have specific reactive loads)

You will land up in a

Power = 1.4 * V * I

Energy Consumed = Power (KW) * Time (Hours)

= 1.4 * V * I * Time(Hours) / 1000

All these are known to you and not provided in the solution

Assuming V=400, I=50, Per day 16 Hrs of load, 30 working days / month it is

= 1.4* 400 * 50 * 16 * 30 /1000

= 13440 Units

which will translate into approx $6720

This is approximate and with lot of assumption, feed your data and get approximate value.

Does Cnpower not help people from other regions or he is just being racist ?

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#6
In reply to #3

Re: KWh calculation for utility power supply

10/17/2008 2:49 AM

sb,

cnpower also loves to help people from Japan just ask Epke .

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#7
In reply to #6

Re: KWh calculation for utility power supply

10/17/2008 3:18 AM

hehe, neednt shout. why not show your calculation? you are very active at motor thread ...

wngito said pinguin dont live in europe. when did you arrive in northern hemisphere?

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#10
In reply to #6

Re: KWh calculation for utility power supply

10/17/2008 4:52 AM

holeinthesnow, why dont act as active as you do in the motor threads?

is it you think the paster comes from africa so neednt to put out your suggestion?

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#11
In reply to #10

Re: KWh calculation for utility power supply

10/17/2008 5:13 AM

cnpower, I am glad to see that you are missing my input. However, I really don't have anything new to add. Enough good suggestions have been pointed out already.

I am sure you will be able to help out, but if you get stuck trying to understand such complex subjects as Ohms law, the difference between DC and AC, the difference between a resistor, capacitor or inductor etc then please just ask wangito or Epke . I am sure they will assist you.

I am glad that you have actually started reading the posts put forward by others - it truly is nice to see.

Kind Regards

Your friend

Mr. W.A Snow

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#12
In reply to #11

Re: KWh calculation for utility power supply

10/17/2008 5:57 AM

ah, do you think which one is the best in the pasts?

give out your opinion. I'm too impression on your action in the motor part. ha-ha.

also noticed that the current is given as 20/40. I would have expected something like 23/40.

400/230 ==2V?

ha ha, current is 0.5 ? I'm just starting with my elementary math.

you appear to be very enthusiasm. and like to find very tiny mistake from others. except yourself.

ohm law is very difficult, you may explain more clear than others.

of cause as well as delta/star connection. i hvnt read your continuous to the motor issues. its not shame by other checked up and found error. hehe

I shall learn dc ac from others out there. I really dont know what they are!!!! hehe. need endeavor.

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#13
In reply to #12

Re: KWh calculation for utility power supply

10/17/2008 6:20 AM

cnpower, what does "400/230 ==2V?" mean ? I am completely confused.

Oh, bye the way I think you should be using the off topic button - it is just a suggestion.

Regards

Mr. W.A Snow

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#14
In reply to #13

Re: KWh calculation for utility power supply

10/17/2008 7:10 AM

hehe, your math is really more better than mine.

doesnt matter, because I dont know ohm law. and ddc aac.

eh, I think its better for me to show all who visit here. in order to leave a good funy material for them laughing at and talking about when work off, during a cup of tea,

" look that lovely chinese, he didnt do such easy math which even a pupil can do it."

hehe. continue, continue, Im waiting for your more suggestion, and more answer about <| / Y.

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#15
In reply to #14

Re: KWh calculation for utility power supply

10/17/2008 7:43 AM

cnpower, Sorry but I still do not understand how 400/230 = 2V (I am assuming that you mean 400Volts ÷230 Volts). Am I missing something very obvious here ? Is this some sort of chinese joke ?

Regards

Mr. W.A Snow

P.S This is clearly off topic so I would suggest you mark it so. That way other viewers need not bother reading this nonsense.

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#16
In reply to #15

Re: KWh calculation for utility power supply

10/17/2008 8:20 AM

no no, not chinese joke but this cr4 joke.

you lost nothing as you are very careful, and know ohm law very well, you can calculate 230/40, you can work out this 10/20 or 400/230 as well.

dont use tipic off function, Im learning abstruse da2c subject from you now. others may be benifit from you , too.

hehe, no shame. Im always curious why current can rotate?

why someone often acts so strangely like a.c.?

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#9
In reply to #3

Re: KWh calculation for utility power supply

10/17/2008 3:39 AM

A power factor of 0.8 seems to be slightly on the high side.

A power factor of approx 0.6 would be a better place to start with.

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#4

Re: KWh calculation for utility power supply

10/17/2008 1:54 AM

while i am not against the calculations ,why dont you just install a KWH meter and build up an accurate history of your consumption ,you may as well get your KWH readings from the utility meter and record.

This will help you in predicting your future consumptions and estimate your monthly bills also.

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#23
In reply to #4

Re: KWh calculation for utility power supply

10/21/2008 7:00 AM

Yes, though it will cost money to pay for instrument C.Ts and the meters. But, installing a KWH Meter or an Energy Meter will make life easy. Where by, from your accumulated energy consumption history, you may some time in the future wish to reduce your consumption through energy reduction methods.

From which you could save money from, say instead of using 36W light fittings, you decide to replace them with their equivalent of eco-lights which will work at 25W with an improved power factor of 0.98. These lights are inbuilt with very good power factor correction devices, and I've seen them work. Or if your from an industrial/manufacturing plant, you may want to improve your power factor correction from say 0.70 to 0.98 and save on money.

Having a good history is important when it comes to improving and reducing energy consumption.

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#8

Re: KWh calculation for utility power supply

10/17/2008 3:39 AM

You did not mention the voltage but i am assuming 400 volts and 0.85 pf.

so your hourly consumption = 1.732 x 400 x 50 x 0.85 = 29.4 kw

daily= 29.4 x 24= 705.6 kwh

Daily costs= 705.6 x 0.5= 352 dollars and 80 cents.

cheers.

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#17
In reply to #8

Re: KWh calculation for utility power supply

10/17/2008 8:26 AM

Where is original author ?

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#18
In reply to #17

Re: KWh calculation for utility power supply

10/17/2008 8:35 AM

sb, The original poster probably got pissed off reading the nonsense going on between myself and cnpower.

Sorry about that.

Regards

Mr. W.A Snow

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#19

Re: KWh calculation for utility power supply

10/17/2008 9:50 AM

Greetings,

Your question was to estimate your utility bill, you can use history (if available) or calculate based upon the load you have and the utility rates in effect,

there are several calcuclations here to arrive at the instantaneous KWH (kilowatthour, one kilowatt demand/used for one hour) consumption, of which getting the hourly history from your utility (which they may have a smart meter to record or if a dumb meter would need to install a meter to record),

but no reference to the rate per hour calculation, electricity may be priced at multiple rates depending upon time-of-day use or it may just be one flat charge irregardless of time of day or day of the week, or month of the year, you can get this information from your utility, the rates may vary by over 100% so they are an important part of the estimation, you may be able to get the utility customer service rep to plug your info into his equations/spreadsheet and give you a quick answer as he will know all the rates for your connection.

there is also probably a minimum service charge just to be connected to the utility.

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#20

Re: KWh calculation for utility power supply

10/17/2008 11:55 AM

Hello All. Iam gratefull for the response. Thanks

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Active Contributor

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#21

Re: KWh calculation for utility power supply

10/19/2008 4:39 AM

Hi,

It is simply power multiply by the time use. Power has a unit of Killowatt and time has it unit of hour from there Killowatt-hour was derived. To calculate basic formula as follows:

P = (1.732)*V*I*P.F.

where:

P - real power

1.732 is sqrt of 3 and this will only be present when your system is 3 phase

V is the volatge system

I is the phase current

P.F. is power factor (basically in a design and consulting firm we always assume power factor to be 0.8 or 80%, for the reason in most country, electric utilly company have fine for a system that's having less that 0.8 or 80% power factor. With this more than 0.8 or 80% power factor system has a discount that's why most larger facilities put capacitor banks to their system for them to increase the power factor.)

KWH will be P*Hour

KWH consumption will be KWH as presented above time the KWH rate of your Electric Power Utility company.

Hope this somehow helps.

You can also, email me to my addresses. CC copy both emails.

bennegregsiman@yahoo.com

bsiman@meinhardt.com.ph

Regards,

Benn Siman

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#25
In reply to #21

Re: KWh calculation for utility power supply

11/23/2010 6:41 AM

1.good answer

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#22

Re: KWh calculation for utility power supply

10/20/2008 1:55 PM

Attached is an example for a welder.

Welder

cost/month
welderampsvoltsduty cyclesIdle KWH
out put per welder

28

480

60

0.28

total hours
Estimated Usage Hours8 hr's per day

666.6666667

based on 3.75 working hours during 250 working days in 07
costelectrical usage per hour (KWH)8.064

at 60% duty cycle

idle usage(KWH)0.28
total per hour

KWH

8.344

cost at

$.082 KWH

$63.55

per welder per month at 8 hr's per day

$127.11

per welder per month at 16 hr's per day

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Anonymous Poster
#24

Re: KWh calculation for utility power supply

07/07/2009 10:27 AM

U need to calculate p = 1.732 X VI cos(phy);

p x no of hrs... u get kwh

kwh x 50 cents.... u get cost to pay..

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