How accurate are these "PSU calculators"?

Runningkid · 24 Apr 2009 at 10:57

hi guys,

Just wondering how accurate are these things? I've been trying to decide what one to get for my up coming upgrade so i've been playing around a bit with the extreme power supply calculator to get a rough idea. Basically i should be looking at around a 400w psu (currently siding with the corsair cx400w as it has 30amps on the 12v rail).

But i just want to know, how accurate are these estimates? I've been very reserved with the calculations so the figure *should* be more than what will be my system. (ie, they didnt have 5050e on the list so i chose the 5200+EE, put down a 4830 although i am probably go for a 4770, everything is calculated to 100% load, etc etc). this came to 365W... which is cutting it close as i won't be expecting the corsair to be outputting at its maximum...

so yeah, would 400w be enough or should i go for something a little more juicy (i am on a tight budget

)

thanks,

RK

pastymuncher · 24 Apr 2009 at 11:09

These calculators are usually over estimating by a fair bit. The rig in my siggy only draws a max of 274w at the wall with Orthos and Fur stability test both running at the same time.

Runningkid · 24 Apr 2009 at 11:12

may i ask how many hard discs you've got? I am planning to have 4.

BAMBI · 24 Apr 2009 at 11:15

You should be more worried about having enough power on 12v rails rather than watts.

Ducky Spud · 24 Apr 2009 at 11:16

I put my system in one of those calculators and it came out as needing somthing like 510W... theres no way it uses that haha. Think they do over estimate quite a bit really

As for hard drives, they use minimal amounts of power, not going to make all that much difference really

pastymuncher · 24 Apr 2009 at 11:28

Runningkid said:
may i ask how many hard discs you've got? I am planning to have 4.

A pair of Western Digital AAKS 320Gb sata drives. Also a Zalman ZM-MFC2 multifunction controller, 3x 120mm fans and 2x 92mm fans.

Janesy B · 24 Apr 2009 at 11:34

They are rubbish.

hp7909 · 24 Apr 2009 at 11:46

I'd go for at least 450W to 'futureproof' it. See 400W (especially that Corsair one) seems to be aimed at someone building a HTPC or a mini-PC with GFX onboard, etc & no plans to upgrade in the near future.

Nowadays, if you check the specs (of a reputable brand) you can't go wrong. Think this power-calculators need to reflect this. Corsair seem to also have one (here).

Ghost-Reaper · 24 Apr 2009 at 12:03

they are very inaccurate, I have actually measured mine and their estimation was over 200W more (and I couldn't select everything I have)

Audigex · 24 Apr 2009 at 18:23

I'd call it inaccurate - one says I need a 500W on a system I happen to know has run very happily on 300W for nearly 3 and a half years...

JonJ678 · 24 Apr 2009 at 18:34

It's better for them to overestimate required power than to underestimate. I think it's a sensible way for them to work.

But hey, my system can't draw more than 300W and it's running off a 860W psu, so what do I know

Audigex · 24 Apr 2009 at 19:56

That's true Jon, better for them to go over than under; at the end of the day it shouldn't cost most people more than about £10-20 on the original purchase if they go 100-200W over what they need, the PC won't draw any more power than it would with a smaller supply. Well, apart from a tiny amount due to being optimised for certain load percentages.

Sasahara · 25 Apr 2009 at 00:15

A PSU should ideally be running at 85% load or lower (I'd aim for a max 80%).

So you get the best efficency, lifespan - running a PSU above 85% of it's rated load for long period is certanly gonna reduce it's lifespan faster.

And how every good the capacitors are, they will age so the PSU will lose some performance over time.

Most calculators take this into account.