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how many watts of power does a typical PSU use by itself?

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Last response: in Components
May 22, 2014 5:03:13 PM

trying to get the power down in my home-built router PC, and was curious, how much power does a typical PSU draw, in watts, if it's just powered on with nothing plugged into it? (i.e., if you plug it into the wall and then short circuit cables 4 & 5 on the 24-pin connector). in particular, i'm looking into a Seasonic SS-400FL2, any ideas on that?

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May 22, 2014 5:28:57 PM

The amount of power the power supply uses by itself is not something you worry about when building a PC but the maximum is usually around 4~18 watts from the fan use and that is the absolute maximum.

That would be the same for that Seasonic PSU.
May 22, 2014 5:33:15 PM

depends on whats connected to a pc and how efficient the psu is. with 80+ platinum your psu will only waste a maximum of around 11% of its intake. if the pc is idle it usually alot less than 80 watts depending on gpu and cpu usage and efficiency.

very hard to say really, although your best bet is a meter like a kill a watt will give you an accurate reading
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May 22, 2014 6:06:30 PM

Jonnyguru does low load testing, for the Seasonic X-400 Fanless PSU it was pulling 3.1W from the wall when he was pulling 2.5W from it. The power needed to run the basic PSU circuits is minuscule, the primary power loss at load is due to the resistances in the switching transistors.
May 25, 2014 12:11:59 AM

thanks for the info folks. came in the mail today, and borrowed a buddy of mine's kill-a-watt. the jonnyguru site was pretty spot on, it's about .5-1W. the entire system uses ~22W idle, ~28 during intense VPN transfers.

appreciate the info all