Question about psu's

Calranthe

Calranthe

Calranthe

Associate
Joined
5 Oct 2007
Posts
620
Hello,
This is something that is probably pretty obvious but I will ask anyway :)

Example corsair HX 620W ATX2.2 Modular SLI Compliant PSU, i'm going for these ones have no worries about them, my question is this.

Is 620w the max or constant?
As in Does the psu always draw 620 even if your system only needs 220w to power the parts?

Or is it like a throttle and it draws what it needs?
 
A PSU will only draw what it needs, slight caveat though because there are efficiency bands for PSUs to work within e.g. a 620w PSU might be at its most efficient between say 450w and 540w loads (haven't actually worked it out properly but it is normally in the range 80-90%). It will be fine with less load but may end up using a shade more power than a PSU working within its optimal range - the amount will be miniscule though and I'd prefer to have a high quality PSU working at less than full capacity than a cheap one working at nearer its limit. :)
 
semi-pro waster said:
A PSU will only draw what it needs, slight caveat though because there are efficiency bands for PSUs to work within e.g. a 620w PSU might be at its most efficient between say 450w and 540w loads (haven't actually worked it out properly but it is normally in the range 80-90%). It will be fine with less load but may end up using a shade more power than a PSU working within its optimal range - the amount will be miniscule though and I'd prefer to have a high quality PSU working at less than full capacity than a cheap one working at nearer its limit. :)
Click to expand...

Cool, so im good getting the 620's and it won't waste energy :)
 
However, most good PSUs are more efficient when under more load. A 620 under a light load probably draws more current from the wall than does a 520 under the same loading. An overkill PSU doesn't really help anything and costs you more money, at the time of purchase and for years to come.
 
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