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PC power supply efficiency

  1. Oct 30, 2015 #1

    When the modern 80 plus power supplies are quoted as being "87% efficient" on 100% load, does this mean that an 80 plus Gold PSU rated at for example 1000 Watts will provide 1000 Watts to the internal PC components, and therefore draw 1000/(0.87) = 1149.43 W from the wall? OR does it mean that an 80 plus Gold PSU rated at 1000W will only supply 870W maximum to the internal components?
  2. jcsd
  3. Oct 31, 2015 #2


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    Science Advisor

    Yes, it should (by definition) do so. Whether it really does, is another question.
  4. Oct 31, 2015 #3


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    Gold Member

    Power supplies are rated for their output power. But, since there are multiple voltages (and multiple loads) the output rating is generally a combination of loads that make the supply look good. I don't know how realistic the ratios (say ratio of 3.3V power to 12V power) are, so it's best to consider the output rating to be approximate.
  5. Nov 1, 2015 #4


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    Like meBigGuy says not all combinations apply. There should be an indication in the manual and frequently on the label what those limitations are (often in amps not watts). I would be skeptical if
    1000W can be drawn by actual pc components.

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