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How We Test Power Supply Units

Efficiency

The 80 PLUS certification measures efficiency at 20-, 50- and 100-percent load of the PSU's max-rated capacity up to the Gold efficiency certifications. For the Platinum and Titanium levels, they also measure efficiency with 10 percent of the PSU's max-rated capacity load.

Simply put, if a PSU has an 80 PLUS certification, then it must have the equivalent efficiency required by the corresponding certification. However, 80 PLUS measures at a mere 23 °C (73.4 °F) ambient, whereas we measure efficiency at a higher ambient temperature. This means that, in many cases, a PSU that is certified to a certain efficiency category fails to deliver the same efficiency at higher temperatures in our tests.

Also, many PSUs are tuned to deliver high efficiency at or above a specified load percentage, usually the minimum that 80 PLUS measures at the corresponding efficiency level. But at loads lighter than that, their efficiency is pretty low. Since many of us run our systems for long periods at low-energy consumption modes, efficiency at light loads can be highly important. So it's wise to pay special attention to our light-load test results.

In our reviews, we measure efficiency at four different light loads: 20, 40, 60 and 100W.

The ATX specification also states that the efficiency of the 5VSB rail should be measured, too. In the table below, you will find the minimum 5VSB efficiency levels that the ATX specification recommends.

LoadEfficiency
≤0.225W< 0.5W to meet 2013 ErP Lot 6 requirement (100V~240V)
≤0.45W< 1W to meet ErP Lot 6 requirement (100V~240V)
≤2.75W< 5W to meet 2014 ErP Lot 3 requirement (100V~240V)

Testing in Standby Mode

In 2010, the European Union released a guideline on Energy Related Products (ErP Lot 6), which states that every electronic device should have below 1W power consumption in standby mode. In 2013, this limit was further reduced to 0.5W. The same year, the EU also released the ErP Lot 3 guideline for computers and computer servers.

This is why we measure the consumption of a PSU in standby mode, which is something that would be difficult without our monitoring software since the readings at such low consumption levels have significant fluctuations. We have to average them over a significant period of time to provide enough accuracy.

  • 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