Are PSU calculators accurate?

E

Emraith

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Dec 16, 2006
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So I figure this will be the easiest way to ask this. I used this tool on http://extreme.outervision.com/PSUEngine to calculate the recommended psu wattage, but is this number accurate? It seems very low. The system I'm shopping for a PSU for is a E6600, 4x1GB ram, 4350 Video card, and 6 hard drives. It's giving me under 200W of power.. Would this mean i'd be perfectly fine to just use a cheapo 400W power supply?

The only reason I question it, is because putting in the build of my regular desktop, it only says about mid 300's..I'd think it would need more
 
I would use it as a simple guideline more than anything else.

Edit: And the PSU's wattage isn't really the issue, it's the PSU's rails themselves.
 
When I compared the calculator results on the Antec site to what I've actually measured, the results looked pretty good. The Antec calculator has quite a few variables related to overclocking specifics and various video cards.

Related to this:
And the PSU's wattage isn't really the issue, it's the PSU's rails themselves.

It should really read "And the PSU's total wattage isn't really the issue", and probably the total +12v rail current/wattage, since just about everything in current PC's is powered directly and indirectly from +12v.
 
Sure, go with that. Semantics more than anything.

Regardless, a crappy 800w PSU isn't going to be as good as a good quality 600w unit, regardless of the numbers they slap on it. But there are plenty of variables involved. Bottom line; make sure your rails are good enough.
 
E.E.L. Ambiense said:
Sure, go with that. Semantics more than anything.

Regardless, a crappy 800w PSU isn't going to be as good as a good quality 600w unit, regardless of the numbers they slap on it. But there are plenty of variables involved. Bottom line; make sure your rails are good enough.
Click to expand...

+1

It sickens me when someone goes and buys a rosewill power supply, claims "Oh its 800W itll easily handle anything". Ill warn them before they buy it that rosewill units are cheap chinese units maid mainly by solytech youngyear or ATNG but they buy it anyway.Then after a few months they go and buy a second card for SLI (after i even warned them it wont handle it)runs fine for about a day, then come and tell me their power supply blew and they think one of their gpu's and motherboard got killed as well from the voltage spike.


PSU is never a place to skimp on quality. However, most people overestimate what they need. For instance, you can pretty easily run two gtx285's and an i7 in SLI as long as nothing is overclocked on a 610W pcp&c silencer.


Honestly even for a low end system like that i wouldnt get less than an Xclio Stablepower/Goodpower, OCZ StealthxStream, lower price pcp&c like the 370W, 400W corsair, etc.
 
Emraith said:
So I figure this will be the easiest way to ask this. I used this tool on http://extreme.outervision.com/PSUEngine to calculate the recommended psu wattage, but is this number accurate? It seems very low. The system I'm shopping for a PSU for is a E6600, 4x1GB ram, 4350 Video card, and 6 hard drives. It's giving me under 200W of power.. Would this mean i'd be perfectly fine to just use a cheapo 400W power supply?

The only reason I question it, is because putting in the build of my regular desktop, it only says about mid 300's..I'd think it would need more
Click to expand...

I'm not sure how you managed that.
I entered the same system with 512MB video, 4x1GB DDR2, 6x7200rpm drives and got 274W.
Factoring 20% capacitor aging if you intend to use the PSU for more than a year and you get 328W.

A "decent" 400W will still power this system OK.

Edit:
cocked up a bit there, I somehow put in a 3850 gfx card.
Your card isnt in the list so I chose 4550 which is a bout 5W more, and got 276W.
I still recommend a decent 400W PSU :)
 
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The calculator isn't as accurate as a multimeter, but it gives you a rough ballpark estimate.

There is a very good deal on the Corsair 400CX right now ($30 AR). It will power your system just fine and is a very good PSU as well.
 
PC_User said:
The calculator isn't as accurate as a multimeter, but it gives you a rough ballpark estimate.
Click to expand...

Unless someone has a clamp on current probe for their multimeter, they aren't going to get very far measuring amps so they can calculate watts.
 
No because they use a CPUs TDP which is nothing to do with the amount of power they use.
 
I've seen people use PSU calculators and come up with weird (usually severely inflated) numbers, perhaps because they're not using it right. So it's always best to double check on these forums, or anywhere people with knowledge of power consumption figures hang out.
 
I find it easier to just eyeball it and making a good estimate, but if you really want to be sure then a good PSU calculator would work.
 
The PSU calculator you posted actually seems somewhat decent. For the system in my sig it recommended a 420 watt PSU which isn't too far from what the system actually needs. I have a 650 watt PSU in the system but that was because I got a much better deal on it than the 550 watt PSU I was originally looking at. That said, when running the system in my sig at full load except for the GPU, I pull about 272 watts from the wall measured by my Kill-a-Watt. Right now, the GPU is also under 100% load so my usage figures for this system are higher than they used to be.

Something to keep in mind is that few people run CPUs or GPUs at 100% 24/7 like I do. Considering I run my systems this hard, I prefer to have a little extra room to play regarding the PSU. It also means I'm going to need to spend a bit more money on a higher quality PSU than most will need. I also leave some extra room for upgrading or adding components. None of my personal systems ever stay the same over time. As I upgrade things in my main system, the components replaced are usually migrated down to my secondary and tertiary systems.

As others have said, you can't afford to skimp on the PSU and a higher price tag doesn't automatically mean a better PSU. While a PSU calculator can be used as a rough estimate for wattage, you still need to look at the power on the rails as well as the overall quality of the PSU itself. When putting together a new system, I always spend more time researching what PSU choices I have and finally deciding on which PSU I'm going to get than I do on any other single component. I probably spend more time on PSU research than any other three components combined.

 
Emraith said:
So I figure this will be the easiest way to ask this. I used this tool on http://extreme.outervision.com/PSUEngine to calculate the recommended psu wattage, but is this number accurate? It seems very low. The system I'm shopping for a PSU for is a E6600, 4x1GB ram, 4350 Video card, and 6 hard drives. It's giving me under 200W of power.. Would this mean i'd be perfectly fine to just use a cheapo 400W power supply?

The only reason I question it, is because putting in the build of my regular desktop, it only says about mid 300's..I'd think it would need more
Click to expand...

this calc is very accurate and includes the most possible variables of any other ive seen. ive been using this calc for years without issue
 
I find that the newegg psu calculator is pretty accurate if you subtract the total by 100
 
I agree with post number 7. Get the Corsair 400CX. Corsair builds solid power supplies. I actually just bought 4 cuz I build computers and for me the most important thing in a computer is the power supply.
 
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