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550W PSU and system needs only 350W = 550W/hour ?

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August 12, 2010 6:07:50 AM

If I buy Corsar 550W and my system takes only 350W , I will pay 550W/hours anyway or PSU will consume only 350 W?
a c 85 ) Power supply
August 12, 2010 6:27:56 AM

This is a bit tricky.

A PSU will only pull the power needed to power your machine. So if you need 350 for your computer it will only provide 350W and not the 550W that its capable of. Did you see what I wrote? I said provide, not pull.

If a PSU is 100% efficient at converting AC electricity to DC, then you'll pull 350W from the wall to provide your computer with 350W of DC power. PSUs are not 100% efficient. An 80% efficient PSU will 437.5W from the wall. A 90% PSU will pull 389W, while those old 70% units from the P4 days will pull 500W.

I bring this up because you used the word "pay". What you pay will depend on how good your PSU is. The worse it is, the more you'll pay.
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a c 85 ) Power supply
August 12, 2010 6:39:32 AM

This is a bit tricky.

A PSU will only pull the power needed to power your machine. So if you need 350 for your computer it will only provide 350W and not the 550W that its capable of. Did you see what I wrote? I said provide, not pull.

If a PSU is 100% efficient at converting AC electricity to DC, then you'll pull 350W from the wall to provide your computer with 350W of DC power. PSUs are not 100% efficient. An 80% efficient PSU will 437.5W from the wall. A 90% PSU will pull 389W, while those old 70% units from the P4 days will pull 500W.

I bring this up because you used the word "pay". What you pay will depend on how good your PSU is. The worse it is, the more you'll pay.
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August 12, 2010 8:38:01 AM

Sounds right to me. The PSU won't use 550W when your PC is only drawing 350W. It will draw a bit more though due to all PSUs not being 100% efficient. Corsair is a good brand so I would guess it would be above 80% efficient.
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a c 85 ) Power supply
August 12, 2010 9:21:31 AM

Depends on the model. Some are, some aren't.
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August 12, 2010 11:11:30 AM

Well put 4745454b...couldn't state it any more clearly.
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