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Efficiency: On or off?

374 Views 9 Replies 7 Participants Last post by  Bennylava
I just wanted to ask a quick question about the efficiency rating for PSU's. My PSU says that it has greater than 80% efficiency, much like many PSUs do today. Well, I assume that means when the computer is on. But what about when it's off? How much power is being wasted by my 1200w silverstone PSU? How can I determine that? Yeah I bought too big a PSU. There is another story for that. But you know how pretty much all electronics use a little bit of power even when they are off? That's what I'm asking here.
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I would imagine that if your pc is off that the psu wouldnt suck up to much power without having it for a place to go.
When your computer is turned off it is drawing a tiny bit of power, but not much at all. The mobo LED, and I think it recharges the CMOS battery... that's about it. Less than a watt, maybe less than a tenth of a watt. Even at 5% efficiency I'd be amazed if your computer drew more than maybe 5W when turned off.

Now if you're talking about power draw when idle, then yes that's a bad situation. Most PSUs get terrible efficiency under about 15-20% draw. Your computer might draw 100W idle, so that's less than 10%. So bad efficiency. I sometimes say that there's no such thing as too big a power supply, but that does have its limits.

Originally Posted by SgtSpike
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Kill-a-watt. Buy one.

I have one!!!

Some fun facts. My sig rig.

PC Off. PSU On. 20W
PC Off. PSU Off. 0W
PC Idle ~270W
PC Folding all 3 GPUs ~475W
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I take it that it's some kind of pulse width modulator or something, that you can use to throttle back your PSU's ability to consume power?
No, it's just a watt meter; shows power draw at the wall.
Sweet I want one.
I hear that they are soon to be releasing 90%+ efficient PSU's. Sort of like a new generation thing.
Yeah somehow I doubt that. 80% is pretty darn efficient as it is. Course I guess you never know..
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