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Power draw while computer is off varies by PSU.

post #1 of 4
Thread Starter 
Now I'm not sure if this has ever come up before - a few searches returned nothing.

I have an OCZ 850W Z-series PSU which is rated 80Plus gold.

Got it on a great sale - it ran a 'server' in my basement drawing 700W (at the wall) for the past few months with no issues. Now that server has been disassembled, I figured I'd toss this thing in my sig-rig and reap the efficiency benefits.

It seemed great. Saved 16W at idle, 35W under load! Awesome! Less heat, less kWh used. Then I turned it off - it draws 7W when the computer is shut down. It even uses 3W with the main switch turned off (what the hell?).

In comparison, the old VX550W draws 1W with the computer shut down and 0W with the switch off. I don't turn off my power bar every time - it's got a clock (among other things) plugged into it. This so-called efficient PSU will not save me a penny, in fact it will likely cost more.

Are there any reviewers that take note of this? I know this isn't an amazing PSU model, but I certainly expected it to perform better than a 4 year old mid-range one...

/end rant
    
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post #2 of 4
How are you measuring? Most monitors have accuracy issues at low loads.
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post #3 of 4
It's called standby efficiency. It varies from PSU to PSU.

Also the cheap meter you're probably using likely isn't accurate at low loads, and may be thrown off, depending on the standby circuit's design. I can tell you that your VX550 uses more than 1W at standby, because your motherboard uses a minimum of ~1W in standby mode.
post #4 of 4
Thread Starter 
Quote:
Originally Posted by DuckieHo View Post
How are you measuring? Most monitors have accuracy issues at low loads.
All I have used (so far) is a UPM Power Meter. I am aware it's far from perfect and I understand a bit of deviation from a cheap device like this, but the fact that nothing else in my household will give such an odd reading says something.

It measures everything in my household to the same watt every time, so a 7 watt deviation on ONLY this PSU? Unlikely.

Quote:
Originally Posted by Phaedrus2129 View Post
Also the cheap meter you're probably using likely isn't accurate at low loads, and may be thrown off, depending on the standby circuit's design. I can tell you that your VX550 uses more than 1W at standby, because your motherboard uses a minimum of ~1W in standby mode.
It will register the different loads of different motherboards in standby. My old P35-DS3L drew 6W when off. It also registeres the change from 4W to 1W when I enable a power save feature in the BIOS (I forget the name offhand, I think it disables WoL).

It's just somewhat ironic to have an "efficient" PSU that will save zero electricity. If reviewers included tests of this it would definitely influence what I purchase. I don't want to buy something that consumes the equivalent of a small CFL 24/7.
Edited by i_hax - 8/8/11 at 11:07pm
    
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