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Power consumption

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dinkdankdo

Junior Member
Hi everyone,

Can anyone tell me if a 400watt psu costs more to run in a PC that is always on than a 200watt psu. The pc i am going to be running is an old P3 866 that i plan to run as a linux fileserver. It has graphics/sound/networking on board, has no monitor and wont be taxed very much other than serving music to my modded xbox.

I need to get a new psu and am really just wondering if there is any benifit in trying to track down a lower powered psu
 
The PSU will only supply as much power as the PC needs. If the PC needs only 100W, then either PSU will give it the same amount of power.
The issue is with efficiency, a 400W PSU will not draw more power than a 200W PSU unless it's less efficient.
A 400W will cost the same as a 200W assuming they are both as efficient as each other.
If you want to minimise the costs, get the highest efficiency PSU you can find.
 
Originally posted by: dinkdankdo
Can anyone tell me if a 400watt psu costs more to run in a PC that is always on than a 200watt psu.
Click to expand...

Unless you want to be very fussy about it, the answer is no!
The power rating of a PSU is the maximum power that it can deliver. It is not the power that it will use regardless of its load.

For example, if you have a 500W PSU that runs a 100W load, it will draw 100W plus its loss from the wall.
The loss has to do with t e efficiency of the PSU. Any PSU has some loss. The higher the efficiency, the lower the loss. Even a 200W PSU has some loss.

Again, just because you have a 500W PSU does not mean that it will draw 500W from the outlet. It will if the PC needs 480W and the PSU dissipates 20W because of its loss.
 
Connect an AC ammeter to the line cord.

A more efficient PSU will use less power. Older PSU are running at 65% efficiency or less. The better PSU units from Seasonic, Fortron, and Enermax can exceed 75% efficiency.
 
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