How powerful power supply do I need?

By azrael · 15 replies
Feb 27, 2006
  1. I am buying a new computer and I decided most of the parts except the case. I am having problems dedicing on the PSU. I find very good cases but most of them are having a power supply at most 350 watts. I am planning to buy the following parts: For the graphic card: ASUS Extreme N6600GT Silencer/HTD, for mobo ASUS P5WD2 Premium, for processer: Intel 3.0GB single core, 1GB RAM, 2 hard drives, one dvd writer, one dvd reader and other small stuff like floppy drive. The case I am looking for will have 2 fans for its own only (other than the ones on the cards) For the case, I am expecting good cooling. Can you help me if I need a 400 watt or 450 watt PSU? And if I need a 400 watt or 450 watt PSU, is it good to replace the PSU in the case with a more powerfull one that I would buy seperatly; may that cause any problem? And lasty, what is the advantage of having a more powerfull PSU than what I need?
  2. N3051M

    N3051M TS Evangelist Posts: 2,115

    advantages of having a powerfull PSU than needed is when upgrading better/powerhungry parts no hassle required, but common sense would be to have more than enough, but not too much to waste $$$...

    you can use this psu calculator to check how much juice you need..

    and a word of advice, brand does matter, as you'd probably encountered reading through this forum.. just search the forums for good brands to get..
  3. azrael

    azrael TS Rookie Topic Starter

    Thanks for your help this site helped me a lot. Which power supply do you suggest for me to use?
  4. seanp789

    seanp789 TS Enthusiast Posts: 111

    for the system you just described 350W should be plenty of power. They issue you will face is that a some companies make lower quality power supplies that will burn out and die under either heavy load or just long term general use.

    I cant list all the bad ones but some good brands are:
    Enermax, Power PC & Cooling, OCZ, SilverStone, Antec, Seasonic, zalman, thermaltake, coolermaster.

    You will probably want an ATX 2.0 PSU with a 24-pin mobo connector or a 20+4-pin.

    This is low budget Aspire psu on sale:
    $29.00. it will get job done on a system like yours

    Here is a quality seasonic for more than double the price:

    And Here would be my personal choice:
    Antec 500W ~$70
  5. Mirob

    Mirob TechSpot Paladin Posts: 478

    Do yourself a favor and stay away from Aspire PSUs. Some have started on fire. :hotbounce

    The other two a very good. Enermax, OCZ, Antec, Seasonic, PC Power and Cooling are some of the top brands.
  6. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    at the minimum 550W your graphics cards will suck a lot of juice.
  7. azrael

    azrael TS Rookie Topic Starter

    Hey I am a little bit confused here, seanp789 is saying that I will need at most 350 watt, tedster is saying that I will need 550 watt and from the link that N3051M I am expected to need a 400 watt PSU at maximum.
  8. N3051M

    N3051M TS Evangelist Posts: 2,115

    well the calculator will give you an approxamate/sometimes minimum watts required, since the maths are for average parts, you can also see if you google different psu calculators that they give slightly different answers..

    350watt psu running at 95% efficiency or a 400w running at 80-90% efficiency would just run your system (i mean just, not recomended)
    and thats for a good quality 350w psu..

    the trick of it, if you want to get your exact power needs, is to look through the specs of each components (on the box or on the website) on how much wattage you need and add it up, plus round up to the nearest 50w to give you a safe level.. and ted's right, if the the vid card is high performance then it will suck up a lot of juice, or anything else high performance for that fact, as well as powered components (firewire pci cards for example)...

    and dont go cheap on the psu, if you need to spend the money spend it well =)
  9. Didou

    Didou Bowtie extraordinair! Posts: 4,274

    A good brand 350/380w PSU should be plenty. I've been running a 6800GT on a 380w Antec for over a year before my upgrade & it worked fine.
  10. azrael

    azrael TS Rookie Topic Starter

    Ok than I think I will go with a good brand 400 - 450 watt PSU to be on the safe side and to get the maximum performance from my system. Thanks for your help all of you. :)
  11. azrael

    azrael TS Rookie Topic Starter

    I had a new question come into my head right now. First of all, the power specifications given by the manufacturers (I mean just in the model name) are the true power or peak power value. And in addition to this do I need to multiply this value with a efficiency factor like 80%-90% (for a good brand PSU of course). Lastly, which of these values should I be comparing with the power need of the system given by the website which N3051M gave for instance.
  12. Mirob

    Mirob TechSpot Paladin Posts: 478

    With a good brand name PSU the PSU will output more than rated, so it's safe to go by the rated outputs. Some lesser brands have alot of power on 5v rail, you will need alot on the 12v rail (I'd gess 25-30amps on the 12v rail, 30-35amps on the 5v and 3.3v will do.) You don't need to factor in efficiency for power output, just overall power consumption.

    Read the stickys here,

    David Hammock is the PSU guy.

    I like these,
    FSP Group AX450-PN, 450W Power Supply
    Antec TRUEPOWERII TPII-480 480W Power Supply
    ENERMAX Whisper II 460W Power Supply
  13. stealthy

    stealthy TS Rookie


    Yes, What Mirob said, "Do yourself a favor and stay away from Aspire PSUs. Some have started on fire. :hotbounce

    The other two a very good. Enermax, OCZ, Antec, Seasonic, PC Power and Cooling are some of the top brands."

    ditto, I just found this out today went to swap out my psu and noticed something here is the pic :
  14. cfitzarl

    cfitzarl TechSpot Chancellor Posts: 1,975   +9

    There's no point in bumping a thread this old.
  15. MetalX

    MetalX TechSpot Chancellor Posts: 1,388

    I don't know about that... Look what I run with an ancient old 460 watt.

    EDIT: Whoops just saw how old that was. Silly me.
  16. Mirob

    Mirob TechSpot Paladin Posts: 478

    When it comes to PSUs quality is better than the numbers of watts it's rated. Even if it's not powerful enough when it dies it wont take the rest of your computer with it (or your house.)
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