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Thread: PSU Poser - more power for less money?

  1. #1
    Senior Member
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    Jun 2006
    London, UK
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    PSU Poser - more power for less money?

    Morning all

    Got a power supply poser for you:

    I was going to buy a 550W power supply for my PC. If I buy a 750W supply instead...

    - will the 750W use less electricity than the 550W to run the same PC? (my logic is it will since it will be running at a lower % of its maximum transforming capacity)

    - I guess it will also run quieter and cooler for the same reason?

    You see, I'm thinking that if I buy the bigger PSU, not only will it give me spare power for if I add to my rig in future, but will actually be cheaper to run and save on energy in the meantime?

    Am I right or wrong?



  2. #2
    root Member DanceswithUnix's Avatar
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    Jan 2006
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    • DanceswithUnix's system
      • Motherboard:
      • Asus X470-PRO
      • CPU:
      • 3700X
      • Memory:
      • 16GB 3200MHz
      • Storage:
      • 1TB Linux, 1TB Games (Win 10)
      • Graphics card(s):
      • Asus Strix RX Vega 56
      • PSU:
      • 650W Corsair TX
      • Case:
      • Antec 300
      • Operating System:
      • Fedora 30 + Win 10 Pro 64 (yuk)
      • Monitor(s):
      • Benq XL2730Z 1440p + Samsung 2343BW 2048x1152
      • Internet:
      • Zen 80Mb/20Mb VDSL
    It just isn't that simple.

    First, your fundamental premise "since it will be running at a lower % of its maximum transforming capacity" is backwards, as a switch mode PSU will struggle to run at low output.

    Then there is the fact that most high output PSUs these days are 2 rail, so you are actually buying 2x275W in a single box if you buy a 550W PSU. I wonder if the 750W is just 3x250.

    Some manufacturers quote an efficiency, but they aren't to any standard so you can't compare them between PSUs (and they will be on reasonable load as that makes them look better).

    Cooler & quieter are down to how well it is designed, which is quite independant of power rating.

    I like my Akasa PSU, which has a single 120mm fan that is quiet unless the machine goes under heavy load. Plenty of other PSUs have a similar design.

  3. #3
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    Nov 2005
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    • vaio's system
      • Motherboard:
      • Gigabyte Ds3 rev1.
      • CPU:
      • Allendale E6300 468 x7
      • Memory:
      • 2 x 512 Guil Ultra PC2 6400 468mhz @ 2.1v
      • Storage:
      • 120 GB Maxtor PATA/Ubuntu-Vista dual boot.
      • Graphics card(s):
      • Sapphire Radeon 1600 Pro.
      • PSU:
      • Corsair HX520.
      • Case:
      • Enermax Chakra.
      • Monitor(s):
      • ATMT 19" tft. (1280 x 1024)
    Look for a supply with high efficiency.......circa 80%.

    Look at Seasonic/Tagan/Antec/Enermax.
    Member Of Crunchers Inc multi project Distributed Computing team-New members most welcome *

  4. #4
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    Apr 2006
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    Here's a great article about PSUs,
    More does not mean have to take into account the manufacturer and efficiency of the unit. Look for something with an active power factor, AFC, for better efficiency but you can't go wrong with the companies named above.

  5. #5
    Senior Member charleski's Avatar
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    Jul 2006
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    The SilentPCReview article also makes the point that, even for well-built PSUs, you're better getting a unit that delivers just a bit more than your actual need, as it will then be operating in the region of peak efficiency. So basically, if you need 500W for your machine, you will be using less power with a 550W PSU than a 750W one, simply because the latter hasn't reached its peak efficiency at a load of 500W.

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