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Choosing the right PSU

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October 15, 2011 2:48:44 AM

Ok, this holiday season I'm working on my third major build for myself, and I plan on heavily using my intel discount for maximum happy.

My REAL question is, "How do I choose a PSU based on the other pieces of my build?"

If nobody really knows the exact science of it, I'll take recommendations for the following build:

CPU: i7 2600k
Mother Board: Asus P8Z68-V PRO
GPU: EVGA GTX 570 HD 1280MB 320 bit
RAM: G.SKILL 8GB DDR3 SDRAM DDR3 1600 Timings at 7-8-7-24
Storage: WD raptor 10k rpm 350 gig, and an SSD, but I haven't decided on the SSD yet.
Cooling: Corsair H80 water cooling kit, 2x 120mm intakes, 1x 120 exhaust (used with the h80) and a 200mm top exhaust fan

OK! So is this psu going to be enough? http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Or should I get something a little more powerful? I'd like to keep it pretty efficient if possible, preferably gold rated.


TLDR: How do I know if a PSU will give me enough power before I buy it?

Also as a side note, what does it mean when someone talks about a piece of hardware "posting?"

More about : choosing psu

October 15, 2011 4:01:02 AM

there r supply calculators

but the most power hungry component of a gaming build is the grahics card

try googling

"GTX 570 minimum power supply"

and Im sure you will get about 146 000 answers in under 0.4 of a second
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October 15, 2011 4:10:51 AM

actually its 3.2 million answers and it took 0.18 of a second
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October 15, 2011 5:03:55 AM

NEVER!cheap out on the psu,It is the most important part of any build,My logic is this,I have always used 1000+ watt psu's,no matter how much i run(crossfire)the psu will never work that hard,thus producing less heat,my corsair AX1200 never breaks a sweat,now if i was running say a 600-750watt,and its running at even 75%,its producing more heat than my 1200 watt.not to mention i'm ready for any future upgrades.

always buy a good name brand psu,do a lot of research,reviews.


the AX750 is a nice psu btw.
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October 15, 2011 7:14:53 AM

Thanks for the excellent advice you guys. I went and found a psu calculator and it told me I would need about 550 watts with minimal capacitor aging. I went and cranked up the aging spec to 50% and the recommended watts jumped up to about 830, so I think I'll upgrade the psu to 850 just to future proof myself a bit. I'll probably go with an 850AX, just a step up from the one I had my eye on.

Thanks again!
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Best solution

October 15, 2011 1:50:58 PM

Capacitor aging is bogus and gives grossly exaggerated results. Any good PSU using 105C rated caps will suffer minimal capacitor aging, over a decade you might lose 15% but many good units are overbuilt by about 20% anyway so it doesnt affect you at all. The AX750 is enough for most dual card setups, the only thing i wouldnt use it for would be a pair of 480s or 580s, but it can handle a pair of 570s just fine if you do SLI in the future.


@earnie, 1kW units are overkill for 99.999% of rigs and are just a waste of money for most, i would take a great 850W over a good 1kW unit anyday and it will cost me less, and you may want to recheck your efficiency math, because the load % doesn't determine how much heat is put out, the efficiency at that load does, so if its a platinum rated 650 W unit it will put out less heat than your gold rated AX1200.
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October 15, 2011 4:07:50 PM

I dont know what it is with Newegg underpricing PC&PC PSU's, but this is a STEAL at the price:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Great efficiency, great reputation, check any review, the quality is fantastic. At the price, I can't really recommend much of anything over it to be honest, and its more than enough for even 2 570's.
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October 15, 2011 9:37:25 PM

hunter315 said:
Capacitor aging is bogus and gives grossly exaggerated results. Any good PSU using 105C rated caps will suffer minimal capacitor aging, over a decade you might lose 15% but many good units are overbuilt by about 20% anyway so it doesnt affect you at all. The AX750 is enough for most dual card setups, the only thing i wouldnt use it for would be a pair of 480s or 580s, but it can handle a pair of 570s just fine if you do SLI in the future.


@earnie, 1kW units are overkill for 99.999% of rigs and are just a waste of money for most, i would take a great 850W over a good 1kW unit anyday and it will cost me less, and you may want to recheck your efficiency math, because the load % doesn't determine how much heat is put out, the efficiency at that load does, so if its a platinum rated 650 W unit it will put out less heat than your gold rated AX1200.


Hmm... Well in that case I'll probably get a platinum rated 750w psu instead of my gold rated 850 that I've budgeted for. I was planning to do a dual 570 setup in the future so that is excellent advice. If I end up getting a 580 or 90 I'll probably upgrade the psu a little bit too.
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October 15, 2011 9:43:27 PM

Nah, i wouldn't pay the premium for a platinum rated 750W unit, the AX 850 has great ripple suppression and voltage regulation which a platinum rated unit for a similar price likely wont. You are talking about only 3% efficiency difference at most which wont save you enough to pay for itself ever.
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October 15, 2011 10:09:42 PM

ares1214 said:
I dont know what it is with Newegg underpricing PC&PC PSU's, but this is a STEAL at the price:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Great efficiency, great reputation, check any review, the quality is fantastic. At the price, I can't really recommend much of anything over it to be honest, and its more than enough for even 2 570's.



That is. I've been looking at upgrading my PSU for OC'ing purposes, I might have to get one of these.

Don't forget that if you plan to do any sort of OC'ing - if you want to run any power-hungry coolers, any sort of custom liquid cooling, or a water block like the Corsair H100, you should definitely add or subtract wattage accordingly.

If you want to run a liquid block I'd suggest looking at the H100 over the H80 - you're more likely to get the most out of OC'ing your CPU that way, what case do you have or plan on using?
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October 16, 2011 2:33:28 AM

Some food for thought:

The "80 PLUS" rating means the PSU runs most efficient between 20-80% of its capacity. I would "guess" that your idle load would be around 120w and your load will be around 600w with very hefty OCing and running some games. The bronze, silver, gold, and platinum means higher efficiency, like 90% for gold.

20% of a 650w PSU = 130w = PASS

80% of a 650w PSU = 520w = FAIL (You would need a "gold" rated PSU to squeeze a 650w PSU)

This is only for efficiency however. Being a gamer and OCer, you need to look at the amps on the 12V rail.

However, Something around 750-800w from a reputable manufacturer will do you just fine. Buying a PSU that is 1000w+ will actually be inefficient because it can't handle such a low idle load very well.

Get PC Power and Cooling 750w $100 with 10% off promo code PCP1010, ends 10/23 $80 after mail in rebate

Now, select me as "Best Answer" and move on with your build :D 
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October 16, 2011 3:16:28 AM

steelbeast said:
Some food for thought:

The "80 PLUS" rating means the PSU runs most efficient between 20-80% of its capacity. I would "guess" that your idle load would be around 120w and your load will be around 600w with very hefty OCing and running some games. The bronze, silver, gold, and platinum means higher efficiency, like 90% for gold.

20% of a 650w PSU = 130w = PASS

80% of a 650w PSU = 520w = FAIL (You would need a "gold" rated PSU to squeeze a 650w PSU)

This is only for efficiency however. Being a gamer and OCer, you need to look at the amps on the 12V rail.

However, Something around 750-800w from a reputable manufacturer will do you just fine. Buying a PSU that is 1000w+ will actually be inefficient because it can't handle such a low idle load very well.

Get PC Power and Cooling 750w $100 with 10% off promo code PCP1010, ends 10/23 $80 after mail in rebate

Now, select me as "Best Answer" and move on with your build :D 


Woah there, I suggested it first! :lol: 
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October 16, 2011 3:19:51 AM

ares1214 said:
Woah there, I suggested it first! :lol: 

You recommended the 950w, which is double the cost for him that will give him no benefit at all. Save for future expansion, even then the savings is marginal.
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October 16, 2011 3:27:32 AM

steelbeast said:
You recommended the 950w, which is double the cost for him that will give him no benefit at all. Save for future expansion, even then the savings is marginal.


Double the cost? :sarcastic:  Last time I checked $109.99 to $149.99 isn't double :lol:  Besides, for an extra $40, you get an extra bit of power for further expansion needs.
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October 16, 2011 3:31:46 AM

ares1214 said:
Double the cost? :sarcastic:  Last time I checked $109.99 to $149.99 isn't double :lol:  Besides, for an extra $40, you get an extra bit of power for further expansion needs.

Sure, it doesn't hurt. However his question was the "right" PSU and 750w is perfect for him. He even has room for SLI and HDD expansion. He can spend the $40 on something else. Sorry, didn't look to closely at the price :p 
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October 16, 2011 3:34:44 AM

steelbeast said:
Sure, it doesn't hurt. However his question was the "right" PSU and 750w is perfect for him. He even has room for SLI and HDD expansion. He can spend the $40 on something else. Sorry, didn't look to closely at the price :p 


To be honest, if he's thinking of doubling up and OC'ing GTX 570s, I think that warrants a bit more than 750w. Would a 750w PSU be good enough, sure maybe, but at that range of performance, its worth it to splurge a bit on a good future proof PSU. I mean almost 1000w for $115 after all the rebates is a steal no matter how you look at it.
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October 16, 2011 3:46:52 AM

ares1214 said:
To be honest, if he's thinking of doubling up and OC'ing GTX 570s, I think that warrants a bit more than 750w. Would a 750w PSU be good enough, sure maybe, but at that range of performance, its worth it to splurge a bit on a good future proof PSU. I mean almost 1000w for $115 after all the rebates is a steal no matter how you look at it.

Yep, that's true. However, PP&C understates their PSUs, it's really closer to 800-850w.
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October 16, 2011 4:59:55 AM

steelbeast said:
Some food for thought:

The "80 PLUS" rating means the PSU runs most efficient between 20-80% of its capacity. I would "guess" that your idle load would be around 120w and your load will be around 600w with very hefty OCing and running some games. The bronze, silver, gold, and platinum means higher efficiency, like 90% for gold.

20% of a 650w PSU = 130w = PASS

80% of a 650w PSU = 520w = FAIL (You would need a "gold" rated PSU to squeeze a 650w PSU)

This is only for efficiency however. Being a gamer and OCer, you need to look at the amps on the 12V rail.

However, Something around 750-800w from a reputable manufacturer will do you just fine. Buying a PSU that is 1000w+ will actually be inefficient because it can't handle such a low idle load very well.

Get PC Power and Cooling 750w $100 with 10% off promo code PCP1010, ends 10/23 $80 after mail in rebate

Now, select me as "Best Answer" and move on with your build :D 



Math...you are doing it wrong.


Efficiency is how much extra power must be drawn from the wall to deliver the DC power, a 650W PSU can deliver 650W of DC power, if its only 80% efficient it will be pulling 812 W from the wall, but it is still capable of putting out 650 W of DC power to the system, a 90% efficient unit will only be drawing 722 W from the wall, thats 90 W less heat. You aren't the only one who messes up the efficiency and multiplies it by the wattage, but its still wrong and confuses people. The wattage rating of a good unit is how much you can draw from it, efficiency has nothing to do with that, efficiency also has no effect on ripple suppression or voltage regulation, there are platinum rated units that are lacking in both ripple and regulation, but there are others that are awesome with both.


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October 16, 2011 5:59:51 AM

Best answer selected by wojci028.
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October 16, 2011 6:09:59 AM

g-unit1111 said:
That is. I've been looking at upgrading my PSU for OC'ing purposes, I might have to get one of these.

Don't forget that if you plan to do any sort of OC'ing - if you want to run any power-hungry coolers, any sort of custom liquid cooling, or a water block like the Corsair H100, you should definitely add or subtract wattage accordingly.

If you want to run a liquid block I'd suggest looking at the H100 over the H80 - you're more likely to get the most out of OC'ing your CPU that way, what case do you have or plan on using?


I looked into the h100, but it's the same surface area for the heatsink as the h80. The h100 just has better airflow since you can do a push pull config on each fan slot instead of having the heatsink all in one fan slot. I read some reviews and watched some videos and I don't think it's worth switching out my case for the minimal performance increase associated with the h100. The case I'm using now is an antec 900 http://www.newegg.com/Product/Product.aspx?Item=N82E168...
I've had a great experience with it so far. Great case for the money.


hunter315 said:
Nah, i wouldn't pay the premium for a platinum rated 750W unit, the AX 850 has great ripple suppression and voltage regulation which a platinum rated unit for a similar price likely wont. You are talking about only 3% efficiency difference at most which wont save you enough to pay for itself ever.


Ah! well in that case I guess I'll just get the ax850. That will give me some headroom if I choose to oc my gpus or something.
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