TechSpot

How to calculate PSU wattage requirements

By herr5407
Jul 12, 2007
  1. Hello all.

    I've done a little searching on these forums and have found a few posts concerning what I need but the links don't work. (or else my laptop at work sucks. which it does)

    Anyways, I was wondering if someone could explain to me the math I could do to determine wattage required for a PC. Can I take a figure off a part i install and then do some math to compare it to the PS wattage?

    This may be the easiest thing ever I just remember reading some complicated thing somewhere. Can anyone explain?
     
  2. halo71

    halo71 TS Rookie Posts: 1,289

  3. herr5407

    herr5407 TS Rookie Topic Starter Posts: 118

    I've seen the calculators before but I'm more interested in calculating the actual wattage myself on paper.

    The journey systems calculator is very nice though. I was just wondering if there was a forumla to follow.
     
  4. jobeard

    jobeard TS Ambassador Posts: 13,446   +324

    P = E * I
    where
    P is power in watts
    E is volts
    I is current in amps
     
  5. herr5407

    herr5407 TS Rookie Topic Starter Posts: 118

    Also found this, not sure if it's correct. A 30% buffer seems fairly large.

    *Formula used = sum of wattage used by devices x 30% (or 1.3) buffer to be safe. And remember fans, cooling devices and anything connected via Firewire(IEEE 1394) or USB also draws power directly from the system.

    Thanks!
     
  6. jobeard

    jobeard TS Ambassador Posts: 13,446   +324

    the 30% is known as a power factor which equates to 1/1.30 or 76.9% loading
    of the power supply. GOOD design says you never run anything at 100% of the
    rating as that shortents the life of the component :(
     
  7. herr5407

    herr5407 TS Rookie Topic Starter Posts: 118

    Ok. I was planning on building a computer in the near future and I've heard of a few people cooking PSU's from overload so I thought I would be safe and calculate it myself to get the proper wattage.

    Thanks for the information jobeard!
     
Topic Status:
Not open for further replies.


Add New Comment

TechSpot Members
Login or sign up for free,
it takes about 30 seconds.
You may also...


Get complete access to the TechSpot community. Join thousands of technology enthusiasts that contribute and share knowledge in our forum. Get a private inbox, upload your own photo gallery and more.