Efficiency Comparison and How to Choose Your PSU

We wanted to explain to you how much power your system should actually use so you can make the best use of your new power supply. Of course you can load these power supplies up to the limit and still have around 87% efficiency - a result that many cheaper power supplies cannot reach even at their ideal load. However, these graphs show you where these power supplies reach their best efficiency.

From 100 to around 400W you will get maximum efficiency if you're on a 115VAC grid. That will provide you with an 88-91-88-percent curve with the 500W unit, an 87-90-89-percent curve with the 600W unit, and an 83-90-89-percent curve with the 700W unit. If you want even better efficiency you would want to be in the darker red area of 100 to 300W output. We've combined all three PSUs on one chart, however, so you will want to consider the curves and adjust your PSU selection as appropriate, e.g. the 700W PSU performs best with a load of at least 150W.

With 230VAC our recommendations look quite different. Users on a 230VAC grid can use any of these three units with any kind of load and achieve very good efficiency. Even at 5% load all of the units are still well above 80%, which is something that was difficult to reach a few years back. If you really want to squeeze the best results out of your units you will want load of at least 100W up to the maximum rated output of the PSU. That is a very large area and it shows how versatile these PSUs are. If your system uses 200W to 600W you will be able to maintain a constant efficiency of over 90%! In short, hook up just about any system to these power supplies on a 230V grid and you can be sure you'll be truly energy efficient.

Just to put things in perspective, the 80 Plus certification was introduced a few years back to put public focus on more energy efficient products, mainly power supplies. In the beginning there was only one certification, but since the initial introduction the group behind the certification has felt it necessary to introduce additional levels of efficiency. Today, we have Bronze, Silver, and Gold, with Gold being the highest level of the 80 Plus and presenting a very difficult target for the PSU manufacturers. The race to Gold has now been won, but now there's a new target in sight: Platinum. The required efficiencies for the different levels are listed below.

80 Plus Certification Requirements
  20% Load (Light) 50% Load (Typical) 100% Load (Full)
80 Plus Standard 80% 80% 80%
80 Plus Bronze 82% 85% 82%
80 Plus Silver 85% 88% 85%
80 Plus Gold 87% 90% 87%
80 Plus Platinum (230VAC only) 90% 94% 91%
Efficiency and PFC Safety Functions and Maximum Wattage


View All Comments

  • 0roo0roo - Monday, February 15, 2010 - link

    simple, to the point, should be done more. Reply
  • JFrizzle - Friday, February 12, 2010 - link

    Where do you get the Enermax Modu 87+ 500W? I can only find the 700W on New Egg, and can barely find the 600W flavor. Have these items been released yet? If not, when is the expected release date? Reply
  • cupoftea - Sunday, January 24, 2010 - link

    I would be really interested to see how this compares to another PSU from Germany, the Nesteq ASM X-Zero 500 semi-passive. Reply
  • KoVaR - Thursday, January 21, 2010 - link

    Really nice PSUs, but a bit shame they come with three 12V rails instead of one "big one" Reply
  • ssj3gohan - Thursday, January 21, 2010 - link

    To be brutally honest here, I would be very surprised to find more than one person in the pool of hardware geeks that are my friends that has a computer that, even under load, consumes more than 300W. Even really powerful gaming machines (say, core i7 + HD5870) usually draws around about 100W idle, and with recent developments usually even less than 80W (yes, really). Under load, these machines barely top 200W. You would need to do some serious skulltrailing to build something that needs 400 or 500W.

    For the serious gamer, a 350W PSU should be the norm - why you ask me? At idle, a single-processor, single-gpu machine uses about 20% of the PSU's rating, and that is where the serious efficiency benefit is for forward converter topologies. Right now, gamers use ridiculous 500+ W power supplies which leaves the PSU uselessly wasting energy at idle, where the computer is most of the time anyway.

    This is by the way also one of the humongous errors made by various reviewers (not anandtech by the way) - they for instance try to test a C2D E5200 (extremely power-efficient) but decide to run it in their usual test bench which inevitably contains a power supply designed for overclocking. Then they're surprised that the E5200 seems to be no more efficient than a Q9600 or something, but in reality the E5200 system consumes so little that the PSU is hopelessly inefficient at that point. If you use this knowledge you can build machines that idle below 35W by just and only using a very low-wattage power supply (barring the truly high-end video cards of course)
  • 7Enigma - Thursday, January 21, 2010 - link

    I'll agree with you to an extent. The 700+ PSU's are more than overkill for most people. But keep in mind the longevity of the PSU. Most people do not like their PSU's running 80% of capacity when under load, and I constantly hear 60% as the sweet spot for long-life. We are now approaching a sort of saturation point for PSU efficiency so I don't see people buying a new PSU every single time they upgrade or rebuild. It was different when we were jumping from 50-60-70% efficiency. But going from 80-82-84-etc is not really that big (from both a utility cost and heat standpoint).

    These new PSU's are great in that they get very high efficiencies at anything pretty much above 20%. Other brands are also almost there (25-30%), so it's kind of moot. You're not going to see large price differences if they made 350 or 400w because the main cost is in design and manufacturing, not so much the difference between parts (some but not the bulk of the cost).
  • Christoph Katzer - Thursday, January 21, 2010 - link


    Check out the street prices, the MSRP of the Modu87+ was 150€ and it's now already at 116€...
  • yyrkoon - Wednesday, January 20, 2010 - link

    "Enermax posted this video on YouTube to show real life experiences and how they could be solved with CordGuard. We think it's dangerous to let kids play behind a PC in the first place, and let's just hope they don't notice the power switch…."

    Or do one of the more creative/inventive things kids have been known to do. Like perhaps try to stuff a peanut butter and jelly sandwich through the fan grill . . .

    But right, I do not think any responsible parent is going to let their young kids play around with the power supply of a computer in the first place. I would think Enermax needs to work on their marketing a bit more . . . The video stinks, and screams "skiddy". CordGuard is not a terrible idea, but come on. Are they really trying to market a $.05 gimmick ? When did the name Enermax sink so low ?

    Personally, I would like to see some aircraft quality (screw-on ) connectors for the removable power connections, and a plain black fan would be perfectly fine with me. Also, I agree that the name badge on the fan guard is not necessary. Yes, I *would* pay more ( fair price ) for the above mentioned connectors.
  • gwolfman - Wednesday, January 20, 2010 - link

    Why is 115VAC so inefficient in comparison to 230VAC? Reply
  • ClownPuncher - Wednesday, January 20, 2010 - link

    I can see the appeal, but for me a single 12v rail over 50a is ideal, rather than 3-4 rails. Reply

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