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How do I know how much power I'm drawing?

post #1 of 4
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Like the title says, how do I know how much power I am drawing from my rig?
    
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post #2 of 4
Sadly, you'll need one of these type guys:
link

I don't know of any power supplies that can accurately report how much power they are actually drawing.
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post #3 of 4
Quote:
Originally Posted by skylarhawk View Post
Sadly, you'll need one of these type guys:
link

I don't know of any power supplies that can accurately report how much power they are actually drawing.
This, there are UPS's that list how much power you're drawing though, but that's only if you're in the market for an UPS instead of just spending ~$100+ on one.

There are online utilities that give an estimate as to how much wattage your PSU should be, you can usually take 15-20% off that value and that's about how much your PC will use under a decent load.

Orrrrr, you could just guesstimate using reviews that list power consumption for your video card & then one about your CPU .
    
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post #4 of 4
Your main power draws are as follows:

CPU
Mwasured in watts as TDP. To calculate a pretty good estimate of power draw from an OCed CPU use this formula. All processors have a TDP watt rating, check the manufactureres website for your chip model. If you aren't overclocking, just use the TDP as the wattage draw of the CPU.

Overclocked Watts = (TDP) x (OC GHz/Stock GHz) x (OC vCore/Stock vcore aka VID) x (OC vCore/Stock vcore aka VID)

As an example use my chip from below: Q6600 G0 is a 95W TDP chip, my VID is 1.237, my overclocked vCore is 1.296, and I'm running at 3.3 GHz up from the stock 2.4 GHz

OC Watts = 95 x (3.3/2.4) x (1.296/1.237) x (1.296/1.237)
OC Watts = 95 x 1.375 x 1.048 x 1.048
OC Watts = 143.4


Video Card
Check your video card MFR for a TDP watt rating for your particular model. I honestly am unsure on the calculation if it's overclocked is the same as for a CPU, but I'd imagine it is, so that's what I use.

Motherboard
This varies a bit, and is generally harder to calculate. Most boards will consume in the realm of 30-60 watts. This includes things like the VRMs, memory, north and south bridges, etc. Check the spec sheet for your motherboard, but I wouldn't expect a lot here.

Hard drives
Check the manufactures webpage for power consumption for your HD model(s). A good rule of thumb is 12 watts per drive for normal operation. As long as you don't have lots of drives, the spin up load really won't be a concern.

DVDRW
Check the model for power consumption, rule of thumb is 25Watts when in use.

Fans
Depends on the fan but it's easy to calculate. PC fans operate at 12 volts. Check the sticker in the center of the fan, it should give you an amp rating. Amps x volts = watts. It's worth considering if you have lots of fans, or fans that use a lot of amps.

Example
A 12 Volt fan pulling 0.5 amps would draw 6 watts.
12 x 0.5 = 6

Thinks like keyboards, and USB devices also pull a little power (a couple watts), but this is negligible.

This should give you a pretty decent rough estimate. I'd shoot for a PSU that will be at ~60% loaded when you factor everything in. This is around peak efficiency for most PSUs, and gives you room for expanding in the future. Also, being "easy" on the PSU and not running ti at 99% load full time helps with longevity as well.

Hope that helps.
Edited by canna - 3/29/11 at 11:43am
2500K 4/1/2011
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2500K 4/1/2011
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