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450watt psu - How many watts DC?

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  • 11-01-2014 12:05am
    #1
    euser1984
    Registered Users Posts: 1,977 ✭✭✭


    Hi, my psu is rated at 450w - does this mean it uses max 450 AC from the wall or 450 dc output?

    Thanks.


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    #2
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    450W output most likely. The AC draw would be more, depends on the power supply but could be 15-30% more.


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    #3
    aabarnes1
    Registered Users Posts: 295 ✭✭aabarnes1


    Assuming your PSU is in a pc or tower, then the output will be +/-5v, +/-12v DC or 0v. The 450w denotes its max AC power consumption.


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    #4
    euser1984
    Registered Users Posts: 1,977 ✭✭✭euser1984


    aabarnes1 wrote: »
    Assuming your PSU is in a pc or tower, then the output will be +/-5v, +/-12v DC or 0v. The 450w denotes its max AC power consumption.

    Layman on this subject but what do you mean by 0v status, and what has that to do with watts anyway? Thanks.


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    #5
    ED E
    Registered Users Posts: 36,167 ✭✭✭✭ED E


    euser1984 wrote: »
    Layman on this subject but what do you mean by 0v status, and what has that to do with watts anyway? Thanks.

    It doesnt. He clearly didnt read the OP. And 0v is the return side, so to put 5v over a component you connect 5 and 0 making the circuit. 12 and 0 for 12.

    Draw will vary. I have parts that should draw about 600W if the specs are to be believed. My 430W PSU pulls 418W full load from the wall. If its around 80% efficient thats 335W to components.

    If you're trying to work out how much its costing, pick up a killawat or similar. Working on rated figures is pretty useless.


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    #6
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    But if you look at a laptop PSU, the rated wattage is actually what it produces on the DC side, not what it pulls from the wall. Most 65W Acer PSUs are 19V, 3.42A which equates to 64.98W. Assuming 80% efficiency that would mean it would draw ~80W from the wall at full load. So I don't see desktop PSUs being any different.


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    #7
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    euser1984 wrote: »
    Hi, my psu is rated at 450w - does this mean it uses max 450 AC from the wall or 450 dc output?

    Thanks.

    A PSU rated at 450W means it can safely supply 450W to the PC.

    The efficiency of the PSU determines how much it draws from the wall at a given load. You also might be interested in the efficiency curve because it varies depending on load.


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