Question on Power Supplies

kitkat9933 · 5 Jan 2013 at 19:35

Quick technical question:

If I have a system that draws 500W and is powered by a 1200W PSU, what will the power drawn from the wall be?

I was under the impression ( I'm no expert) that the components will draw the power they need and will be supplied this power. Since 700W of the 1200w of capacity isn't needed surely it won't be produced by the PSU?

RJC · 5 Jan 2013 at 19:37

what are your system specs?

The PSU will only pull whats needed, my system at full load pulls 330 from the mains, my PSU is roughly 80% efficient so in theory my actual components are drawing 264w~

wazza300 · 5 Jan 2013 at 19:37

thats right,im not 100% sure but pretty sure it uses what it needs,the psu is capable of 80% of its rated output higher for silver/gold rated psu's but will only generate whats needed ect

kitkat9933 · 5 Jan 2013 at 19:41

wazza300 said:
thats right,im not 100% sure but pretty sure it uses what it needs,the psu is capable of 80% of its rated output higher for silver/gold rated psu's but will only generate whats needed ect

Yeh I am pretty sure it only uses what is needed as-well since power can't just be dispersed.

It isn't to do with my spec just a pure theoretical example, that came up in discussion today that's all.

olivier renault · 5 Jan 2013 at 20:12

There's just a little bit less efficient. Bit like an engine torque curve, where they operate best in a given range. Although we're talking about a few percent efficiency fluctuation.

Tealc · 5 Jan 2013 at 21:50

In your example an 80% efficient PSU will draw 625W from the wall and need to dump 125W of energy as heat. A 90% efficient PSU will only need to draw 556W from the wall.