How accurate are these "PSU calculators"?

Associate
Joined
1 Dec 2005
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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
 
Associate
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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
 
Soldato
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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).
 
Associate
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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...
 
Soldato
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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 :)
 
Associate
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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.
 
Soldato
Joined
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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.
 
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