Test Equipment and Methodology

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700W, a Rigol DS5042M 40MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox, and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

Cold Test Results

At room temperature, the Seasonic S12G 650W unit easily honors its 80 Plus Gold certification, reaching up to 94.4% efficiency at 50% load. Inside the normal operating range of the power supply, which is between 20% and 100% load, the efficiency remains above 90% at all times. In fact, if the S12G was just a little more efficient while heavily stressed, it could hit 80 Plus Platinum status.

As expected, the efficiency drops sharply when the load is below 20% (130W in this case), dropping down to 76% with a 32W load, but it goes up to 84% when the load is increased to 65W. These are considered "out of range" conditions and do not affect the 80 Plus certification of the unit, but considering many modern PCs will idle at 40-60W, it's still worthwhile to look at performance at these loads. Of course, at 32W load the difference between 75% and 85% efficiency only amounts to around 5W at the outlet.

Both the air and the heatsink temperatures might appear a little high for a unit of this capacity and efficiency operating at room temperature, but that is because the fan of the Seasonic S12G 650W PSU is being "lazy" -- or "quiet" if you prefer. The fan is thermally controlled and it looks like Seasonic decided it didn't need to spin faster under such testing conditions. During our SPL testing, the fan reaches audible levels only after the unit hits ~80% of its rated output.

The Seasonic S12G 650W PSU Hot Test Results


View All Comments

  • Samus - Saturday, March 1, 2014 - link

    Just buy a PCP&C 750 Quad and take the fan out/unplug it. I've had mine like this for 5 years. It doesn't even get warm pulling 300 watts. JohnnyGuru found it to be the coolest running PSU he ever tested at full load, so running 1/2 load doesn't even require active cooling. They have no electronic noise.

    They're $50 used on eBay.
  • tosisgray - Saturday, March 1, 2014 - link

    Thanks! That's the kind of testing I want to see. Embarrassingly, I have not heard of JohnnyGuru before. I will look him up. Reply
  • geniekid - Monday, March 3, 2014 - link

    I've owned 4 Seasonic power supplies. One of them had coil whine, and it wasn't fanless. Reply
  • nagi603 - Thursday, April 3, 2014 - link

    I have an X-400. Best PSU I've ever bought. No buzz, no problem of any kind. Reply
  • MuteyM - Friday, February 28, 2014 - link

    Going forward, it would be nice if the graphs used Wattage instead of Load % on the X-axis. This would make it easier for people to compare differently-rated PSUs for their own particular needs. For example if I know my computer idles around 50W and maxes at 400W, I could compare all reviewed PSUs and see which are the most efficient at my particular use cases.

    With Load % as it is now I have to manually do a bunch of math for that comparison.
  • GiantPandaMan - Friday, February 28, 2014 - link

    Good idea. Or they could just dual axis it. Reply
  • E.Fyll - Friday, February 28, 2014 - link

    That actually is a very good idea. I will see if I can make a dual axis graph or simply replace the % axis with wattage. Thank you MuteyM. Reply
  • lever_age - Friday, February 28, 2014 - link

    It's only Seasonic's X and Platinum lines that use the San Ace fan. All others pretty much use an ADDA.

    Also, the B in AD1212MB-A70GL should indicate it's a 2BB fan, not hypro. This is the model used in most of their power supplies and often even the ones they build for other brands.
  • lever_age - Friday, February 28, 2014 - link

    ...that is, in the current lineup. Prior M12D or whatever previous high-end model may have also used San Ace. Reply
  • Flunk - Friday, February 28, 2014 - link

    Not to nitpick, but if you're putting together a "powerful cyptomining system" you generally don't use a case at all. Not only that, but you're going to need more powerful or multiple power supplies. Reply

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