What size PSU will I need for this build?

NS_frostbite

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I'm unsure what size PSU I will need for my PC build. I've tried several websites that give estimated wattage, but some say 500W and others say 900W, so it's not really helpful. I'm thinking of getting an EVGA SuperNova 850W power supply but according to some sites this might not be big enough. These are my planned specs:

MOBO - ASUS x99 PRO
CPU - Intel Core i7 5820k @ 4.5ghz
RAM - 16GB DDR4 RAM @ 2666mhz
GPU - EVGA 980TI HYBRID @ 1500mhz core clock
CPU COOLER - Corsair H110i GT
CASE - NZXT H440 / x4 120mm fans
SSD - 3
HDD - 1
Other peripherals - Mouse, keyboard, external HDD, headphones, USB stick, webcam

Any advice would be appreciated :)
 
Solution
Outervision's Extreme Power Supply Calculator is a reasonable estimate of power requirement, it is based upon TDP values for various component models/series. I would trust it the most but all of them are open to error. Another way to guess is to take the component TDP values from each individual manufacture, add them up and add 50% to the value. This will be a safe bet. FYI, overclocking can dramatically increase power consumption.

For the build you have listed I would say a 600W would be okay with no overclock and 800-850 with an overclock. EVGA's recommended PSU size for the 980 Ti is 600W. Some people will say this is too large and an overestimate but I like to have lots of headroom for transient spikes. Better to be 200W over than 20W under.
 

NS_frostbite

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That calc tells me 880W estimate. Even though i'm sure an 850W would be fine, I think i'll spend a little bit more on the 1000W for peace of mind.

 

giantbucket

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mobo + ram + ssd = 50W or so
your cpu = 140 before OC'ing, so let's say 200W
your gpu = 300W at peak settings (directly from EVGA's own web site)

so 550W when everything is running full, which is clearly not ALL THE TIME. a 600W would be ok if it's reliable and you're not running benchmarks 24/7. anything over 800W is just a waste.
 


I believe that to determine the effect of overclocking you will find the following is a reasonable model (there are better ones):

http://physics.stackexchange.com/questions/34766/how-does-power-consumption-vary-with-the-processor-frequency-in-a-typical-comput

TDP increases in a linear fashion for changes in frequency and quadradically for changes in voltage. That is

W(total) = ((1+x) + (1+y)^2)*P where P = TDP, x is the % change in frequency and y is the % change in voltage

Since the TDP for the 5820k is 140W we have for a 25% increase in frequency (3300 to 4150) and 20% change in voltage (1.2 to 1.44)

W(total) = ((1+0.25)*(1+0.2)^2)*140 = 252W

or a 112W (80%) increase in power consumption. As a way of check Outervision's calculator shows system load going from 520W at stock to 624W OC'ed.

But what if all this theoretical physics stuff is off the mark, what about the real world?

In this AnandTech thread they managed to vary the system power consumption at the outlet for a 2600k system from approx. 150W to approx. 360W by changing only these two factors.

http://forums.anandtech.com/showthread.php?t=2195927

That's a 140% increase in power consumption. My increase was 33%. Perhaps my estimate was a bit over, I didn't realize that this processor could only be bumped up by about 0.1V. But then we haven't even talked about the 980's power consumption during overclock. I would bet that my estimate is not beyond belief.
 
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