# How do i calculate the cash im spending with a 24\day pc turned on?

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rickzor

August 24, 2007 11:25:13 AM

Lets take this for example, i have a computer that im using along with a webcam to criate a time lapse video, for that i'll need that have it turned on for about 4 months with no reboots whatsoever (offtopic: its taking 1 picture each 20 minutes for a whole period of 4 months, in order to get a 5 minutes video when compiled @ 30fps\s)

And for that im using a pentium 3 450, a s3trio 4 mb agp, and a usb webcam, a small fan to refresh the webcam and no soundcard or cd drives etc. Im wondering how can i calculate the amount of euros im spending each month, knowing that the total wattage of the system is 125 watts, and my electricity company take 0.90€ per kilowatt.

Are those 125 watts the wattage it consumes per hour or something? Im only missing that in order to calculate the amount of money ill be spending.

Thanks in advance.

And for that im using a pentium 3 450, a s3trio 4 mb agp, and a usb webcam, a small fan to refresh the webcam and no soundcard or cd drives etc. Im wondering how can i calculate the amount of euros im spending each month, knowing that the total wattage of the system is 125 watts, and my electricity company take 0.90€ per kilowatt.

Are those 125 watts the wattage it consumes per hour or something? Im only missing that in order to calculate the amount of money ill be spending.

Thanks in advance.

More about : calculate cash spending day turned

johngoodwin

August 24, 2007 12:27:36 PM

My system has a 500 watt PSU, but idles at about 150Watts or so.

Assuming your machine really did use 125 watts, that would be per hour, so it would go like this:

125 Watts *24hrs per day = 3000 Watts used per day or 3KWhr

3KWhr * 0.90€ per KWhr = 2.7€ per day

You may want to verify your rate is 0.90€ and not 0.09€

If your rate is 0.09€ instead your calculation would be:

3KWhr * 0.09€ per KWhr = .27€ per day

If your system actually only uses half that, your cost would be half.

I hope this helps.

John

rush_123

August 24, 2007 12:44:02 PM

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pete4r

August 24, 2007 1:24:41 PM

rickzor

August 24, 2007 1:57:11 PM

About the 125w value, it was kinda random, i know that the wattage displayed on the psu isnt the actual wattage being wasted, orelse i would pitty the 1k psu owners!

What i wanted to really know is that if the actual wattage being used by the system (say its 80\100w) is the wattage being wasted each hour, if so johngoodwin is perfectly correct in his calculations.

The system:

p3 450 about 25\30 watts

s3 trio agp card about...10 watts? (lol)

usb cam 5 watts i guess..

6 gb hdd 20 watts

cpu fan + another small fan...10 watts?

It isnt that much if in the end, but for the final effect i want for my time lapse video, i'll need it turned on for a very very long time period, hopping it wont die of cold ( not likely ) or hotness or humidity from my balcony.

The cpu has about 46% usage all the time, peaking to 100% every 20 minutes when the webcam software takes a shot, so i guess it wont wastes much electrical power.

hubbardt

August 24, 2007 2:07:27 PM

mike99

August 24, 2007 2:19:38 PM

valis

August 24, 2007 2:52:48 PM

HPCE_Larry

August 24, 2007 3:35:59 PM

sepayne21

August 24, 2007 4:10:09 PM

Just make sure your units are correct in the end, and you won't go wrong most of the time.

1Watt * 1 Hour = 1 Watt Hour

or, 125 Watts * 24 Hours = 3000 Watt Hours

you can always multiply by 1 and not change anything. Since 24 hours and 1 day are the same thing, you can multiply by 24 hours and divide by 1 day, you are still multiplying by "1". your result will be a bigger or smaller number, but your units will differ.

now, 125 Watts * 24 hours/day * 30 days/month * 1 month = 90000Watt hours or 90 kWH

notice how day cancels our of the numerator and denominator and month cancels out which leaves you with Watt and Hour are the only thing left.

now multiply the price/kwh * kwh

kwh once again cancells out of the numerator and denominator leaving with nothing but the end price.

little_scrapper

August 24, 2007 4:32:48 PM

KyleSTL

August 24, 2007 4:57:18 PM

DJ_Jumbles

August 24, 2007 5:02:31 PM

altazi

August 24, 2007 5:10:09 PM

BTW, don't forget to use a good UPS.

Altazi

rockyjohn

August 24, 2007 5:16:02 PM

The tough part is estimated the watt usage of your system. Keep in mind that the load varies and will go up from standby, sitting idle, light load, and heavy load - with gradients in between. How much you actually use the system, the loads, and your power option selections all affect the amount of power used.

Also, if doing a calculation by computing the usage of different components of your sysem, keep in mind that you have to consider the PSU efficiency - in essence the power used or wasted (mostly in the form of heat) by your PSU itself. Most PSUs operate with 70-80% efficiency - and for most it varies depending on the load. So for instance if I calculated from the other components that my computer used 300 watts at full load, then the power used by a 70% efficient PSU to provide the 300 watts would be 429 watts (300watts/70% - or 300watts/.7).

I did a quick calculation and if I used my system at full load of 350 watts 24 hours per day for 365 days per year with a 70% efficient PSU at 13 cents per KWH, the annual cost would be $570. Glad I don't use it that much. Note that at that level changing to an 80% efficient PSU would save me $72 per year.

valis

August 24, 2007 5:44:23 PM

rickzor

August 24, 2007 9:43:20 PM

omgitslong

August 24, 2007 10:05:48 PM

huhwahhappen

August 24, 2007 10:28:39 PM

rsetter1

August 24, 2007 11:17:50 PM

dragonsprayer

August 24, 2007 11:40:24 PM

rsetter1

August 25, 2007 12:07:37 AM

nhobo

August 25, 2007 1:15:53 AM

rsetter1

August 26, 2007 2:54:26 AM

Now you're ready to calculate. Look on the meter for something that says "Kh X.X", where "X.X" is some number (often 7.2). Plug your numbers into the following formula:

3.6 x Kh factor

----------------- = kW

number of seconds

For example, your Kh factor is 7.2, it took 60 seconds for the disc to spin once. Your check showed you were using (3.6 x 7.2)/60 = 0.432 kW, or 432 watts.

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