Are higher power PSUs more efficient at lower Wattages?

[SiM]

I was just thinking...

PSUs lose efficiency when running close to their rated spec. Right?
Say for example a 400W PSU vs a 600W PSU (otherwise homogeneous). Both with specs needing 380W. Because of heat/you are pushing the 400W PSU more, the 600W will be more efficient?

Or is this hypothesis nonsense?

[kalniel]

Sort of nonsense - they're less efficient right at the top of their rated power, but chances are you won't be near that and you'll actually lose more by way of efficiency in the low end.

Have a read up of this good article:

http://www.anandtech.com/casecooling...oc.aspx?i=3413

[SiM]

Good article.
It looks like for coolermaster 900W PSU, efficiency starts to drop at 700W...

For the lower end systems looks like lower the wattage the better, although some PSUs drop off efficiency sharply. The Thermaltake TR2 300W drops pretty steeply from 200W onwards

It is interesting that the Enermax 625W Pro82 dominates other PSUs (including Corsair 450W) at all wattages...



and it does look like 850W PSUs are better than 650/700W PSU for 275+W systems...




So I guess I will get a Pro82+ 385W or a 400W corsair for my file server then

[moogle]

They don't lose it until they're running into peak and getting hotter and hotter. Higher power PSU's have their highest efficiency point in the range that we would be running our PC's (assuming Core2Duo mid/high end) at idle and load (if the peak is wide enough to cover that range of watts)

Before buying my PSU I always checked reviews and even the 80Plus website to look at their efficiency curves.

[SiM]

w00t I have most efficient corsair

[Webby]

Oh yeah just to throw another variable into the mix, efficiency changes with input voltage so we British get higher efficiencies than them that live on other side of pond!

Take the Corsair HX520 for example (image pilfered from Corsair and rehosted )


As you can see higher input voltage = higher efficiency, and to make things interesting it is not a step change (ie the difference is not constant) so unless reviews are measuring efficiency at your local voltage take them with a pinch of salt as while you can predict the efficiencies will be higher with higher voltage you can not say how much, each PSU may have a different trend.

[moogle]

Oh yeah just to throw another variable into the mix, efficiency changes with input voltage so we British get higher efficiencies than them that live on other side of pond!

One of the reasons to <3 UK, it's one of the things I didn't like in USA is those ****ty plugs (no offence). I like our earthed plugs