Efficiency Comparison

The problem most users do not realize today is that if you have lower wattage units you cannot really have the latest technologies inside since it just doesn't make sense. Fancy components and features costs money -- it doesn't matter if they are in an 800W or 300W unit. If you make a small power supply with very high quality features, the user will need to pay for it. The unfortunate truth is that there would be nobody out there willing to pay $150 for a 300W power supply because there are tons of options with prices starting as low as $20. The important thing is to know why you want to have a better quality product, which for most people today is the higher efficiency these units can deliver. If you have a price difference of $50 from your product of choice to a higher efficiency power supply with similar specs, then it will most probably not make any sense since you will need to run the power supply for several years 24/7 to overcome the initial investment.

We discussed this in our article about power consumption and why it is so important to know more about your PC and its components. With today's products we see 82% as a mark every high-end product should be able to reach, which is why we start from 82% with a green graph. Everything below will be red just to show you the efficiency wasn't that good. Don't be worried about the first graph of each power supply since that represents 10% load and no power supply that went through our hands was ever able to come even close to 80% with such a low load. This is why 80 Plus certification for example starts at 20% load. The second graph represents 20% load, the third 50% and the last represents full load. Here again, the more green bars a power supply has the more efficient it is. All of the efficiency results shown are with 230VAC for ease of comparison; efficiency will be slightly lower on 120VAC.


Since the manufacturers are primarily focusing on higher wattage power supplies with new technologies that bring better efficiency, we didn't expect any miracles today. However, some units again stand out from the crowd. Many of the power supplies reach 85% efficiency, which is a very good development. Power supplies from Enermax, OCZ, PC Power & Cooling, Silverstone, and Thermaltake show very good results. The Silverstone Element tops out at incredible 89% efficiency, which puts it at the top of the group a second time.

The following graphic shows the efficiencies below 80% which wasn't possible to include before. Please note the efficiency at 10% load of the FSP OEM unit is with only 61% not visible.

Acoustic Noise Comparison Cable Length - ATX Connectors
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  • Origo - Monday, January 12, 2009 - link

    How can Silverstone Element ST40EF 400W get so good score on quietness and efficiency compared to Silverstone Element Plus ST50EF-Plus 500W?
    This (SPCR) review says Silverstone Element Plus ST50EF-Plus not that quiet or efficient:
    [url]http://www.silentpcreview.com/article670-page1.htm...[/url]
    Reply
  • 7Enigma - Wednesday, January 07, 2009 - link

    Could you comment on this PSU? I know you have a 500 and 550w article coming up but an incredible deal ($25 after rebate) came up on this PSU and I'll snatch it up for my build if it's good.

    Thanks.
    Reply
  • Markstar - Wednesday, January 07, 2009 - link

    As usual, thank you for your interesting review and the effort you surely put into it!

    Greetz from P3D!
    Reply
  • yehuda - Sunday, January 04, 2009 - link

    This is the kind of article I like to keep in my favorites and refer people to. Reply
  • Noya - Saturday, January 03, 2009 - link

    I skimmed through, but I didn't see what type of set-ups you'd recommend for this class of PSU.

    So, I'll post what I'm using with a Corsair vx450:
    Q8200 @ 3.3ghz (475x7)
    8gb Ballistix DDR2-800 cas4 @ 475mhz (4x2gb)
    Evga 9800gtx (stock clocked for now)
    Gigabyte P-45 UD3P
    3 x 7200rpm sata disks
    2 x DVD/RW
    3 x 120mm fans

    It's been running fine for almost a month now (thanks MS for the 30% eBay cashback lol). I previously used this vx450 in my first build (s939 Opteron/7600gt).
    Reply
  • OddJensen - Monday, January 05, 2009 - link

    The VX450 is a pretty good PSU and under optimal conditions you can probably draw more than the max. rated wattage (450W @ 50C ambient). Though personally I like to go with a bit more headroom taking future upgrades into consideration. Reply
  • kenyee - Friday, January 02, 2009 - link

    That's another way to group the power supplies.
    That's one reason I still use Enermax Liberty power supplies...they're a nice small size for HTPC's and the modular connectors are important when there isn't much space. Using this affects power efficiency which is probably why the highest efficiency ones don't use them...
    Reply
  • proci - Thursday, January 01, 2009 - link

    its a very nice test, i like it. i miss some words from the ripple side, they could be useful to those, who don't want to analyze so many graphs.

    i have an FSP 500 GLN60 (active pfc, smooth oemgrey color:D), i wanted a BS2, but the two seems to be identical to me (ok, it only has one 6pin connector). and i'm out of connectors (6molex, 4sata... with 7 HDDs/opticals, 2 fan controllers and only one video card). so having many connectors is a good thing, although you can buy molex duplicators (only downside is they cost money). and its still more than enough to power my system (q6600@3.0, hd3870, lots of vents, hdds...).

    and most of the computers are fine with just 200-300W. its a shame, that there aren't that many good PSUs on the low edge, because having a monster of PSU means you will have bad efficiency in idle with most of the computers. ofc you can build a computer, which eats up 1000W, but besides skulltrail its hard, and mostly needs enthusiast end water cooling/compressor for cooling purposes.

    and having a good PSU is like having good safety in your car: you only notice it when it fails, but then it is already too late. and buying a noname PSU means that you playing russian roulette all the time...
    Reply
  • Martin84a - Thursday, January 01, 2009 - link

    I find it weird people keep recommending Sea Sonic. I'm currently loojing for a new PSU in the 500-600watt range. I remember toms 24 hour PSU stress test, where Enermax, Zalman, Cooler Master and Silverstone where the last remaining, while Seasonic had failed with the rest.
    http://www.tomshardware.com/de/stresstest-netzteil...">http://www.tomshardware.com/de/stresste...etzteile...
    I just read Hardocps Seasonic S12II-500 watt psu review, and the transient load test showed awful results.
    http://hardocp.com/article.html?art=MTM2NCw3LCxoZW...">http://hardocp.com/article.html?art=MTM2NCw3LCxoZW...
    Think computer showed a lot of undervoltage ripple too, and on the 12v a lot of switching between overvoltage and undervoltage. That doesnt look good.
    http://www.thinkcomputers.org/index.php?x=reviews&...">http://www.thinkcomputers.org/index.php?x=reviews&...
    And i have read about the DOA Seasonics too, and the ones failing after some time...
    Seasonic also only provide 3 years of limited warrenty here like many other places, while a brand like Cooler master give 5 years, just like Corsair.

    Just makes you wonder.
    I think i'll go with an Enermax modu+ or pro+ this time..still not sure though.
    Reply
  • sprockkets - Sunday, January 04, 2009 - link

    Hmmm... your first link is to the german side of Tom's, and while we can make out perhaps the SeaSonic PS failed, searching the English side for the same article does not yield a proper counterpart, and the article that comes close to it, is not even finished and broken. What does that say about Tom's Hardware?

    Your second link does show some iffy parts, but overall, they recommend the power supply and dismiss the transient load results as not important. Btw, you think a computer motherboard is going to fry because the 12v line varies 0.2v? 4.92 volts is bad? Those voltages can vary 10% on the 12v line and 5% on the others and meet Intel's ATX spec. Welcome to the real world of imperfection.

    Three years vs 5 years, so what? My FSP power supply in the thrid computer I've built in 2001 still runs fine, and it came with only a 1 year distributor warranty. In fact, only 1 out of 10+ FSP power supplies died, and it probably died because the power strip blew.
    Reply

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