Which PSU wattage calculator should I trust?

I saw these two calculators but got very different results from them. I'm not sure which to trust. Any help is much appreciated. This one told me 550 to 600 watts.

and This one told me ~350 watts.

Here are my build specs:
CPU: Intel Core i5 3570K

Mobo: Asus P8Z77-V

Video Card: ATI Radeon HD 7850

RAM: Corsair 8GB (2 x 4GB) DDR3 1600

HDD: 500 GB 7,200 RPM SATA 6.0

Optical: DVD-RW

Right now I'm going with a 750 watt PSU from Antec. I figure better safe than sorry.

I don't plan on overclocking right now but in the future I think I will.
24 answers Last reply Best Answer
More about which wattage calculator trust
  1. the antec 750w is overkill unless you plan to add a second 7850

    an antec 550w is plenty for a single card.
  2. I use my own calculator.

    A 380w psu would run those components with room to spare, the 7850 only uses 110w. However for overclocking and upgrading down the road I'd recommend a quality 500w unit. Anything else would be overkill unless your running dual video cards.


    This is a good deal too, but not quite as efficient as the antec or seasonic

    Note the Seasonic has a 5yr warranty vs. 3yrs for the others, but it's slightly less powerful than the antec. 2x22a vs 2x20a.
  3. Best answer
    Dont bother with Calculators!

    Basically, no matter what system you have, a minimum of a 500watt PSU should be used IMO, they cost next to nothing so theres no real excuse to go lower.

    Even if your system will not demand 500watts, its still a good idea to if you upgrade you dont have to upgrade the PSU too.

    Anyway, for youre specific system, a 500 watt will do it just fine, though a 550 to 650 would give you some nice headroom.

    BUT: This is important, Brand > Watts.

    Just because a PSU states its 500w dont just buy the cheapest one, always go for a well known reliable brand.

    Heres a example of a PSU to AVOID!:

    And heres a suggestion of a PSU you should consider getting:
  4. No matter what system you have a minimum of 500w should be used? lol

    A 500w would be fine for ANY single video card and overclocking that cpu. Of course I mean a quality 80+ bronze unit as a minimum.
  5. Lol!No you don't need 750Watt you could run two 7850 off 750W and still have breathing room this PSU is for you don't worry it's more than enough ;)
  6. Gallarian said:

    Basically, no matter what system you have, a minimum of a 500watt PSU should be used IMO, they cost next to nothing so theres no real excuse to go lower.

    while the former part of that statement is your opinion, the latter is pure ignorance.
  7. Pure ignorance? A little insulting don't you think.. kinda no need for that.

    When I say system - I mean Gaming system, not just your average desktop, and seeing as the OP was referring to a high end gaming system, then I felt I was right in saying it.

    I just dont see why you'd need to go lower than 500w when they hardly cost anymore than getting a 300/400.
  8. (comment removed - accidental double post)
  9. You probably entered something wrong (or missing) in the second one.

    On my components both sites recommended something around 650W ( which happens to be exactly my PSU, a Corsair TX650 )
  10. Some issues w/ calculators:

    1. Manufacturers, when investigating a warranty claim, don't care what calculator you used. If ya want ya warranty honored, best meet the manufacturer's published specifications.

    500W (or greater) power supply with one 75W 6-pin PCI Express power connector recommended
    600W power supply (or greater) with two 75W 6-pin PCI Express power connectors recommended for AMD CrossFire™ technology.

    2. Calculators must be used correctly...... things like capacitor aging must be properly addressed

    3. Calculator's don't address GPU overclocking.

    4. Calculators state what is necessary to "run the box", not to get stable overclocks. Voltage stability and ripple get worse the closer you get to the max wattage rating...... So, with a 575 watt draw on a 650 watt PSU, you might be just fine with regard to minimum power being provided, but your voltage may be wavering up and down in response to varying demand such that the voltage control circuitry of your components is taxed and this may have an impact on the stability of your OC. As a result, ya may be limited to a 4.7 GHz CPU OC instead of a 5.0 or a 1180 MHz GPU OC instead of 1250 Mhz.

    5. Keep in mind that PSU's hit their peak efficiency point at 50% load.

    6. Ya really don't save any significant amount money typically by buying a lower power quality PSU|17-207-014^17-207-014-TS%2C17-207-015^17-207-015-TS%2C17-207-011^17-207-011-TS

    650 watter costs ya $87, $93 delivered
    750 watter costs ya $90, $90 delivered
    850 watter costs ya $95, 101 delivered

    For twin 7850's, tho 600 is what the manufacturer states is the minimum, I'd buy the 750 for the headroom, efficiency and lower price.
  11. Only a cheap power supply reaches it's peak efficiency at 50%......a good quality psu keeps it's peak efficiency up to 90%.

    Calculators often overstate your needs, obviously for their own protection. The main users are cpu and gpu, the rest is minimal and almost always under 100w. So if you have a 65w cpu at stock speeds and a HD7850 (110w) at stock speeds you can guarantee that your system is going to use less than 275w and a 380w psu would be more than sufficient.

    This would also be classified as a GAMING machine. So Gallarian's theory is ridiculous.

    I'm runing a 150w gpu overclocked and a 65w cpu and I figure my power usage at around 250w max, so my 380w is fine even if I upgrade to a HD7870, I'll have plenty of headroom.
  12. It is not my theory - it is merely an observation that sub 500watt PSU's cost almost the same as a 500w PSU, so therefore you may as well just get a 500w and give your self some clearance.

    Christ.. I thought Toms was a place for people to give advice, not refute other peoples opinions and insult them for it.

    Anyway, this thread was a guy asking for suggestions on a PSU for his system, not a generic discussion on power usage.
  13. We gave our suggestions. You state you were talking about a gaming rig, well many gaming rigs don't need 500w psu's, besides these were your actual words:

    "Basically, no matter what system you have, a minimum of a 500watt PSU should be used"

    Which is a ridiculous statement, my gaming rig doesn't need a 500w psu, a Dell doesn't need a 500w psu, a HP doesn't need a 500w psu, a HTPC doesn't need a 500w psu. So really what you mean to say is ANY HIGH END GAMING MACHINE should have a minimum 500w psu.

    And they don't cost basically the same, you pay for what you get. I paid $30 for my 380w, the CX430 is only $35 after rebate right now.

    CPU's and GPU's are getting more efficient, so you don't need the huge psu's you used to need for a gaming system. For instance high end cpu's used to be 125w, now they are 77w. My HD5850 uses 150w, a HD7850 uses 110w. So a top of the line Ivy Bridge i7 and a HD7850 use roughly 187w, plus add 100w max for other components and you come up with approx. 287w under FULL LOAD, so even a 380w psu would have nearly 100w of headroom if your not overclocking. Also keep in mind there are very few real applications or games that are going to use your cpu AND gpu to full load.
  14. Where did I say that they need that wattage? No where. I simply said they should be used - not that they NEED to be.

    and as I explained, the reason I said they should is because the price is so similar that it doesnt make sense to go lower - the UK the difference between a 400 and 500 can be less than £10, if you spending £800-1000 on a rig, thats nothing.

    I dont see why youre getting so uptight about it like.. but w/e the OP has his answers.
  15. Your not going to find the same psu make and model of 400w for $10 less than the 500w model. It does make sense to go lower, you save money.

    Who's uptight?
  16. Dollars no, but pounds yes

    Corsair CX430 - £37

    Corsair CX500 - £45

    Corsair CX600 - £52


    So within that series, 100 watts is worth an extra £8-11.

    Look mate I dont want to argue with you, its not what Toms is for! :) Your of a much higher rank than me, so I accept you will most likely know more than me - but within the UK, my observation seems to be right, though pricing maybe different in the US.
  17. Thanks guys. I decided to go for a 550 watt Antec BP550 Plus. It was on sale for $50 and it's modular which is a nice bonus.
  18. Great - good luck with your build! :)
  19. Those prices aren't even close in the US.

    Corsair CX series is garbage, that's why they are so cheap. You get what you pay for.

    The regular CX aren't even 80+ certifed, the V2 are barely 80+ certified.
  20. My god.. still want to argue.. Im just not gunna reply, the thread has served its purpose anyway.
  21. Best answer selected by acg651.
  22. geekapproved said:
    Those prices aren't even close in the US.

    Corsair CX series is garbage, that's why they are so cheap. You get what you pay for.

    The regular CX aren't even 80+ certifed, the V2 are barely 80+ certified.
    +1 it's true
  23. wooo a great debate....

    throught the entire scenario, one basic principal is neglected that should be kept forward while considering a psu and that is

    PSU power is not determined by the watts that are mentioned on the unit but the amperage on the available rails. I have seen 500w PSUs with 18a on the rail which everyone will agree is a no buy.

    so if ur psu is offering a decent amount of amps on the rails such as a 500w offering 32a on 2 12v rails, which will give u 32x12= 384w of actual power, now consider which hardware u plan to plug in.

    and do not forget capacitor aging, while buying a psu, always consider a decent headroom to cope up with the aging in the coming years.
  24. lol.. I just saw this old thread now. If i was the OP i would have chosen geekapproved's comment as best solution (and not gallarian's).

    Valve's Steam prototype has i7 and Titan and still 450w psu (80Plus Gold) ?

    I would say if u have money then go for double the recommend wattage shown by calculators just because u get highest efficiency on 50% load thus maybe saving some electricity bill.
    If u are on a restricted budget then just consider the recommended wattage(but choose a good quality psu)

    i prefer outervision's calc
  25. Hey guys.Just wanted to asked you if this PSU is good for my copmontents.I got V650S 80 Plus Gold Coler Master 650w and i got I5-4670k (clocked to 4,2GHz whit 1,7 voltage) and MSI GTX 760 2gb OC Gamin also overclocked (TDP 125 %), Evo 212, Kingstone SSD 120gb,500GB HDD,1LED Vent 120mm and 2 regular for case 120mm,motharboard is MSI z87-g45. Soo what do you think ? And yeah 2x4gb Kingstone hyperXblue ram memory.
  26. I am running 3 sata HDD with 3 deepcool icedisk 2 coolers on asus m4a89gtd pro/usb3 mobo,Amd Phenom II x4 965BE, cm hrper n620 without overclocking,with g.skill 4x4 ddr3 ram[16gb],g.skill trubulance II,Sapphire HD 6870 1GB gddr5,with 10fans, in cm haf 922 with corsair hx650watt psu 80+ Gold. & extreme power supply calc says its using 470watt,coolermaster outerversion says : 444watt . which one should I grant for headroom calculation for future upgrades.
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