Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz 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.

Seasonic PRIME Titanium Efficiency
(~25ºC Ambient Temperature Testing)
% Titanium
650TD 750TD 850TD
10 90% 93.1% 93.2% 92.9%
20 94% 94.2% 94.2% 94.1%
50 96% 96.3% 96.2% 96.1%
100 91% 94.8% 94.8% 94.8%

We usually expect to see an 80Plus Titanium certified unit to borderline pass or even fail the certification requirements during our testing. This is because we are supplying 230V AC to the unit and most models have been optimized for an 110V AC input, as the certification requirements are significantly lower and makes it slightly easier for the designer to meet them. Seasonic positively surprised us because all three of the new PRIME Titanium units are extremely efficient, easily meeting the stricter 80Plus Titanium performance requirements with an input voltage of 230V AC. The top efficiency of all three units is ~96.2% when operating at 50% capacity, with a nominal load range (20%-100%) efficiency average of 95.1% (650W model) to 95.3% (750W/850W models). The low load efficiency with the PRIME Titanium PSUs operating at 10% capacity is above 84.5%, which is much higher than the peak efficiency many low-cost PSUs can hope to achieve. Still, the efficiency of the units once they reach 20% capacity is so high that the thermal losses actually seem to drop instead of increasing.

Please note that we had the hybrid fan mode disabled during our testing in order to showcase the low load noise levels with the fan turned on. With the hybrid mode turned on, the fan starts when the load reaches about 20-25% of the unit’s rated capacity.

The internal operating temperatures of the Seasonic PRIME Titanium are very low, which is to be expected with such an efficient design. The cooling fan initially appears to have a “ladder” behavior, increasing its speed in steps in relation to the load, but the thermal control circuit is actually linear. When the units are operating in an ambient temperature environment, the speed increases are just very small in relation to the fan’s operating range, which appears as a step-like behavior on a chart. The fan of any of the three units did not even reach 50% of its rated speed at maximum load under these operating conditions, operating way below its optimal range and barely reaching audible sound pressure level figures.

The hybrid fan mode is the only thing that does not make much sense with these three units. If the setting is set to off, the fan will start as soon as the PSU is powered on regardless of the load, but will still retain its minimum possible rotational speed until the thermal control circuit decides that it needs to spin faster. The fans of the PRIME Titanium units are inaudible when running at such low speeds. If the setting is turned on, the fans will start before the point they become audible with the setting turned off, meaning that there is no practical difference at low loads whether the fan is spinning or not. Considering that the fans of the units are inaudible when spinning at their minimum speed, it might be wise to keep the hybrid mode turned off. Lower operating temperatures can only increase the longevity of a PSU, even one as good as this one.

External and Internal Design Hot Test Results: Hot Box at 45-50ºC
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  • emn13 - Saturday, April 8, 2017 - link

    Higher rated PSUs necessarily have reduced low-load efficiency, even PSU's as good as these. So it's highly unlikely the 600W fanless is a 1000W model minus the fan; that would significantly reduce the efficiency at low loads, which, given their aim with these models, I seriously doubt is a tradeoff seasonic would have been willing to make.
  • SkipPerk - Wednesday, May 3, 2017 - link

    Seasonic makes a 500W fanless unit, but it is simply a 1350W unit without the fan and some big heat sinks. Enermax also makes robust fanless units up to 500W, but they are basically the same high-wattage unit with the fan removed and larger heat sinks. You might as well buy a 1200W or 1350W PSU that does not spin up until it hits a certain wattage (usually 300W to 400W).
  • Lolimaster - Friday, April 7, 2017 - link

    Considering they're titanium, most people just use 1 gpu and don't OC their cpu. They should launch more models, like 450-550w with fan.
  • blahsaysblah - Saturday, April 8, 2017 - link

    Not that i wouldnt have minded getting one, but read the wiki on 80 Plus. Gold is plenty fine. Im very happy with my SFX Corsair SF450 PS that has never turned on its fan(GPU is GTX 1060 6GB). Never seemed hot to touch. A good GOLD PS seems to not generate enough waste as heat to matter. Its almost one year since using it in new PC.

    Of course its positioned nicely, big vent up, for convection, per fine print, and its right under a vent, SilverStone SG13B case. One 140mm fan upfront is only system fan. Its does not get noisy level RPMs either. (just get silverstone atx to sfx adapter that is vented, centers PS, dont get corsair one. last i checked a year ago...)
  • blahsaysblah - Saturday, April 8, 2017 - link

    dang, no edit. i want to add, i made my own set of power cables(all) to de-clutter build. so my experience may be slightly different than yours.
  • djscrew - Friday, April 7, 2017 - link

    Oh wow, the reviews are in and our product is exceptional. Now let's see if we can improve these margins! How would we go about that? Let's see... maybe we can find a manufacturer who can do it for less.
  • surt - Sunday, April 9, 2017 - link

    Online reviews are absolutely merciless when manufacturers do this, it has killed the sales of more than one vendor over the years. Remember OCZ?
  • Solidstate89 - Friday, April 7, 2017 - link

    Interesting. Has Seasonic moved away from Sanyo Denki fans? I thought they used them exclusively?
  • FriendlyUser - Friday, April 7, 2017 - link

    Great review as always. Having a good PSU is essential for the longevity of the components. I mean, what's the point of the 16-phase VRM design of your MB if you are feeding it crap power? And how far can you overclock your GPU if your 12V line is full of ripple and noise? The efficiency is the cherry on top.

    Being a very satisfied owner of a Seasonic Platinum 850W, the only reason I'm not buying the Prime is because the Platinum is already extremely good and it's powering my home server 24/7 for years now.
  • Lolimaster - Friday, April 7, 2017 - link

    You should probably change for the 10-20% efficiency, which your server will run at most of the time.

    That's why lower than 600w Titanium PSU's are more important than useless 750-850w where low load efficiency is not as good.

    Looking at the numbers you're getting 90% efficiency at near 35w load on the 650w vs 90% efficiency at 55w on the 850w model.

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