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How can I calculate power consumption of my PC in Watt?

I realize this question is difficult to answer as it would be different based on users location, what there PC is doing and what hardware it consist of, along with other factors but I am hoping someone could give me a very rough estimate.

I have always run many PC's in my home 24/7 and I am just now looking at it from a money/cost of electricity point of view.

  1. I live in Central Florida. Can anyone guesstimate/estimate the average monthly or daily cost of running your average PC? Intel quad core processor, 1 SSD drive for OS and programs and 4-5 1-2 TB hard drives in a RAID setup for data. 750watt PSU. What would your guess be?

  2. Also is there an accurate way to figure this out (non-super technical and confusing to a non-math person please) Also I have seen those kill-a-watt devices, do they figure this kind of stuff out for you?

  3. Does a larger PSU make your PC consume more power?

Thanks for any help, you can most likely tell I am somewhat lost about this!

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marked as duplicate by quack quixote, random, Josh K, Troggy Mar 25 '10 at 14:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
this has been asked before: superuser.com/questions/16889/power-supply-capacity-formula .. superuser.com/questions/17683/… .. superuser.com/questions/123009/… (yesterday) .. possibly others –  quack quixote Mar 25 '10 at 0:46
    
Those questions are about the amount of power used by a PC at peak voltage for all components. This question is about the monthly cost of running a computer at mostly idle capacity all the time. –  marcusw Mar 25 '10 at 0:53
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@marcusw: money/cost issues are too localized for this site; they will change and not be relevant in 6 months. how to calculate power consumption is relevant, but it is a duplicate of the questions i listed earlier. –  quack quixote Mar 25 '10 at 1:02

2 Answers 2

Not necessarily relevant for a home user, but commercially one would also calculate the additional hardware maintenance cost -- turning the host off and on increases the chance of something breaking, contacts coming loose, etc. If I remember correctly, commercially, it wasn't worth turning hosts off overnight (particularly if software maintenance was done overnight), but over weekends it was.

Mostly, that shows how little difference it makes (pennies either way).

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FWIW, in 30+ years of using computers, I have never even heard of a case of a computer failing that could possibly be due to powering down and up on a regular basis. –  Lawrence Dol Mar 25 '10 at 5:42
    
I'll just say that I have. Some cases involved machines with high power draws, particularly ECL based hardware, some involved contact points that shifted as internal temps moved from ambient to operating. Tiny movement each cycle, but eventually led to intermittent contact. –  mpez0 Mar 25 '10 at 15:15
  1. Figure out the power usage of your computer. It's hard to know exactly without using a measuring device (Like those 'kill-a-watt' things). You can search online for people with similar computers and see how much theirs use.

  2. Figure out the cost of your electricity. It's measured in $ per kilowatt-hours.

  3. The formula you need is:

(watts used by your PC)/1000 * (hours per month you run the PC) * (cost of electricity).

For example, if your PC uses 200 watts, and you run it 24/7 (720 hours per month), and your electricity costs $0.15 per kilowatt hour, then the cost per month would be: 200/1000 * 720 * 0.15 = $21.6

These are just random numbers, you'll need to plug in your actual numbers. Note you cannot use the 'watt' rating from the side of your PC, that's just the maximum output. Not the actual amount being used.

Sidenote: larger PSU usually doesn't make your PC consume more power. But it can be less efficient than a smaller one, so it might use slightly more power from the wall to provide the same amount of power to your PC components.

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+1 Kill-A-Watt device. Works great and will be very accurate. –  Dave M Mar 25 '10 at 11:51
    
I disagree that this question is a duplicate. This machine is already built and he wants to know how much it uses, not calculate the power required in order to properly size the power supply on an unbuilt machine. In that case, the Kill-a-watt device recommended by DaveM is exactly what should be used (for the average homeowner, anyway... I would use my split cord and PT ammeter)... that would also answer the secondary question about the larger power supply using virtually no extra power on a given system. –  Darr247 Apr 5 '10 at 20:33

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