Efficiency and PFC

With the 80Plus Silver badge, we expect very high efficiency results. Just to clarify, an 80Plus certification requires that a power supply reach 80% efficiency at loads from 20% to 100%. 80Plus Bronze requires at least 82% efficiency at 20% load, 85% efficiency at 50% load, and 82% efficiency at 100% load. 80Plus Silver bumps the requirements up to 85%/88%/85% for the same 20%/50%/100% loads. In short, the Cooler Master 900W UCP had better be able to reach 88% efficiency.




The results meet the 80Plus Silver requirements, actually reaching a maximum of 89% efficiency, but it's important to note that this is only possible on 230VAC. The 80Plus standard doesn't specifically state whether the efficiency should be measured on 230VAC or 115VAC, so we will have to give Cooler Master the benefit of the doubt. 115VAC users "only" get 87% efficiency. [Ed: Boohoo.] Regardless of how you look at it, this is the highest efficiency we have measured in a retail power supply to date.

Before you get too carried away with the high efficiency, however, we need to rain on your parade a bit. The 80Plus Silver badge means that most users will get at least 85% efficiency, but even 20% load represents a power output of 180W, which for an idle system represents a significant amount of high-end hardware. Optimal efficiency starts at around 350W, which pretty much means you will need a quad-core system with dual graphics cards as a reasonable minimum (and probably a bit of overclocking) in order to get full efficiency from this sort of power supply. But then you hopefully already realized this when you saw the 900W rating.


Another part of the 80Plus certification is that the power supply needs to reach at least .9 PFC, but it only needs to achieve this at 100% load. Needless to say, that's not a very difficult requirement to meet, and this PSU has a lower PFC than we have seen with most recent power supplies. PFC goes up with lower input voltages, but most power supplies easily break .99 PFC at lower loads with 115VAC. That said, the difference between .98 and .99 PFC obviously isn't very great, so this isn't something that should seriously concern potential buyers. The result could have been better, but it's not something to lose sleep over.

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  • andlcs - Wednesday, July 30, 2008 - link

    Solid polymer capacitors are ELITE brand.
    http://www.chinsan.com/product/index.asp?id=22">http://www.chinsan.com/product/index.asp?id=22
    Reply
  • sheh - Tuesday, July 29, 2008 - link

    20% load efficiency at is lower than 85% regardless of input voltage.
    Reply
  • strikeback03 - Tuesday, July 29, 2008 - link

    IIRC they test by the ATX methodology, not the 80Plus loading, which might account for the difference. Reply
  • MrOblivious - Tuesday, July 29, 2008 - link

    Or it could be the unit to unit variation, the different temperature, or the different load pattern, etc. ;) Reply
  • JarredWalton - Tuesday, July 29, 2008 - link

    Definitely true. The 80Plus loading methodology differs from the standard ATX loading, and that can easily account for the 1-2% difference between what Christoph measured and what CM reports. Reply
  • MrOblivious - Tuesday, July 29, 2008 - link

    80Plus does list what the requirements for certification on each test report (115v 60hz) and the load steps used to accomplish them. You can see the UCP report here: http://www.80plus.org/manu/psu/psu_reports/SP215_C...">http://www.80plus.org/manu/psu/psu_repo..._MASTER_...

    They don't list the temperature there but IIRC it is 25c (will have to check when I get home). Also, 80 Plus Silver is 85-88-85% not 82-85-82% as it seems to be indicated.
    Reply
  • tomoyo - Tuesday, July 29, 2008 - link

    I was just about to mention this as there's some misinformation on 80plus scattered about in the article. Hopefully you'll clean that up soon. To me it's a pretty big achievement to get 85-88-85 at 25C on 115V on a huge 900w psu like this one. One thing I've noticed is that some of the new low power psu models are showing extremely high low wattage efficiency such as 90-92%. Some of these include the two dell 80plus silver models and some of the new actel ones. 80plus Bronze is much easier to achieve as most 80plus psu's are already near 85% in the middle range. Reply
  • JarredWalton - Tuesday, July 29, 2008 - link

    "80Plus Bronze requires at least 82% efficiency at 20% load, 85% efficiency at 50% load, and 82% efficiency at 100% load. 80Plus Silver bumps the requirements up to 85%/88%/85% for the same 20%/50%/100% loads. In short, the Cooler Master 900W UCP had better be able to reach 88% efficiency."

    I'm not sure how that's at all confusing. As to the UCP 900W actually achieving Silver in our tests, it does appear to fall just short at the 20% load mark, but only by ~1% (84% efficiency when it's supposed to be 85%). I'm not going to worry overly much on that point, as there's a certain margin of error in testing.
    Reply
  • MrOblivious - Tuesday, July 29, 2008 - link

    "Before you get too carried away with the high efficiency, however, we need to rain on your parade a bit. The 80Plus Silver badge means that most users will get at least 82% efficiency, but even 20% load represents a power output of 180W, which for an idle system represents a significant amount of high-end hardware."

    Since that is NOT what 80Plus Silver means it could be a bit misleading.
    Reply
  • JarredWalton - Tuesday, July 29, 2008 - link

    Ah... I see my typo. I put that paragraph in, and apparently hit a 2 instead of 5. Should be 85% there, you're right.... Reply

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