How We Test Power Supply Units

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Our methodology, testing equipment, and benchmarks.

A PSU should be able to keep all of its rails within some predefined voltage ranges at all cases/loads. In Table 1, you will find these ranges (following the ATX v2.53 specification). With the introduction of ATX v3.0, there are some differences in load regulation since the new standard allows for higher voltage drops at +12V, up to 7% on all connectors but PCIe ones, where the voltage drop can go up to 8%.

DC Output Voltage Regulation

Swipe to scroll horizontally
Voltage NameRangeMinimumNominalMaximum
+12V1±5%11.40V12.00V12.60V
+12V2±5%11.40V12.00V12.60V
5V±5%4.75V5.00V5.25V
3.3V±5%3.14V3.30V3.47V
-12V±10%-10.80V-12.00V-13.20V
+5VSB±5%4.75V5.00V5.25V

Here's an example of a voltage regulation test results chart you'll find in each of our PSU reviews:

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Aris Mpitziopoulos
Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a contributing editor at Tom's Hardware, covering PSUs.

30 Comments Comment from the forums
  • JPNpower
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.
    Reply
  • Nuckles_56
    Really good article, it is now nice and clear how you guys go and test the power supplies, and as JPNpower said, no one can fault you guys for not being thorough enough.
    Reply
  • ykki
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.
    Reply
  • Kewlx25
    Interesting!
    Reply
  • damric
    Looks legit, Aris.

    THW used to be the laughing stock of PSU reviews, but your recent reviews have changed all of that.

    Keep up the good work!
    Reply
  • damric
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.

    I'll make one and submit it through bb-71 to get stickied.
    Reply
  • ykki
    15570872 said:
    I'll make one and submit it through bb-71 to get stickied.

    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.
    Reply
  • damric
    15570891 said:
    15570872 said:
    I'll make one and submit it through bb-71 to get stickied.

    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.

    It will be a group effort for sure :)
    Reply
  • iam2thecrowe
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.
    Reply
  • ykki
    15571045 said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.
    Or more fake reviews.

    Reply