Seasonic is one of the oldest PSU manufacturers and they are a very experienced company. There is no randomness about the products they design; each and every one of them serves an exact and specific purpose. This is also true for their two latest additions to the Platinum series that we have tested here today. With the power requirements of typical computers in constant decline, it is known that such powerful units have a very limited target audience.

Both of the units that we tested here today share the same external and internal design, with the only difference being the ratings of some components. Externally, the understated appearance and fully modular design will be appreciated by users. The design of the sides is a little tricky, as whether the user will be seeing a sticker with electrical specifications or decorative engravings depends on whether the PSU will be installed with the fan facing downwards or upwards.

Internally, we found an advanced full-bridge topology platform, components of the highest quality and an immaculate soldering job. The assembly job confounded us somewhat, as it is rather messy and we were surprised to see such a thing in a Seasonic product, but it should not really affect the performance or reliability of the PSUs. Besides, Seasonic covers these units with a seven year warranty, removing any concerns that we could express about the longevity of these units.

What both of the new Seasonic Platinum units really excel at is electrical performance. Both units displayed excellent energy conversion efficiency and outstanding power output quality, with the Platinum SS-1200XP3 slightly outpacing the Platinum SS-1050XP3. It appears that the more powerful components of the 1200W version give it a slight performance edge as well, despite the identical platform. They also maintain very low operating temperatures, even when heavily loaded and in adverse environments, yet at the expense of acoustic comfort. However, we do believe that very few users actually require their system to remain silent while it is heavily loaded.

The majority of the users that actually have to buy a >1kW PSU are either hardcore gamers or cryptocurrency miners. What hardcore gamers want is ample and clean power for their multi-GPU gaming system, ensuring its stability. Gamers also often seek good aesthetics, as their systems frequently include cases with windowed side panels. A gaming system requires very high power when loaded but just a small portion of it while performing simple everyday tasks. With the cooling profile that Seasonic's Platinum series has, the units will be quiet while the system is idling, discernable only when it is heavily loaded (i.e. while the gamer is actually gaming), and thus it is unlikely that any environmental noise will overcome the sound from the speakers or headphones.

Cryptocurrency miners on the other hand simply require highly efficient units that can sustain a continuous heavy load. Energy conversion efficiency is required for obvious reasons; when such a system is working 24/7, energy losses are important both financially and practically, as they cost the user money and heat up the unit, reducing its lifetime and performance. Seasonic's Platinum series units however have aggressive cooling profiles that will keep their operating temperature very low, even while the PSU is heavily loaded. Their efficiency at high loads is excellent as well, surpassing 92%. The seven year manufacturer warranty is the cherry on top for users that plan on running cryptocurrency mining rigs with these units, and likely the other components of the system will fail long before the PSU gives out. The high speed of the fan will definitely make these units loud under such conditions, but that is of little importance for cryptocurrency mining rigs.

The Seasonic Platinum SS-1050XP3 currently retails for $230 and the 1200W Platinum SS-1200XP3 can be purchased for just $20 more at the time of this review. Considering the small price difference and the slightly better performance, the 1200W version potentially offers a better value, though if the pricing gap widens, the 1050W version may become more appealing. As far as competition goes, Seasonic's new units are considerably cheaper than most of the competitive products. The Platinum SS-1200XP3 is $50 cheaper than Corsair's AXi series (e.g. $300 after rebate for the 1200W version), but it's simpler and without Corsair's Link interface. It's also cheaper than Cooler Master's V1200 Platinum ($300 as well, though it's only $252 on Amazon), with the only actual competition coming from the Leadex-based EVGA Supernova P2 1200W ($232 at the time of this review).

Ultimately, the number of use cases for 1kW and higher PSUs is rather limited. For cryptocurrency mining rigs, the good price and specific performance profile of the Seasonic Platinum units makes them an excellent choice. Of course, GPU mining has become generally unprofitable at this stage, so buying a new $200+ PSU could take the better part of a year to break even. Gamers on the other hand will have to consider other factors as they decide whether the Seasonic Platinum units can fully cover their needs or if they require the features and/or different performance profile of another model. Seasonic delivers high quality PSUs with their XP3 series, and does so at reasonable prices, so if you're in the market for such a power supply they're worth a look.

Seasonic Platinum SS-1200XP3 Hot Test Results
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  • SodaAnt - Wednesday, September 3, 2014 - link

    I still tend to be slightly annoyed at the low efficiencies with high power PSUs at around 5% load or 50-75W. I noticed the article even said "Obviously using a 1200W PSU to drive a 60W load on a regular basis would be rather odd, so in most use cases the efficiency will be much higher." However, I don't really think that's true. Maybe that would have been the case 5 years ago, but now even monster rigs will easily use less than 100W when they are just idle at the desktop, which is a surprising amount of time. Further, there's quite a large subset of users that get a 1200W power supply, yet use it in a build with a single GPU and CPU, merely because they think they might upgrade later.

    In short, efficiencies at the low end should be higher.
  • LtGoonRush - Wednesday, September 3, 2014 - link

    76% efficiency at 5% load is EXTREMELY efficient, especially for a high-current power supply. There's a certain minimal overhead to power the electrical conversion hardware, and while it doesn't affect semi-passive models, the fan alone can account for 5% or more of efficiency losses at 50W draw. This overhead is also affected by the capacity of the power supply, as larger or parallel components increase overhead. The fact that a 1050W power supply is only wasting 12W of power at low load is quite respectable, and means that any improvements would have very minimal benefit.
  • SodaAnt - Wednesday, September 3, 2014 - link

    I think that wasting 12W of power at low load is actually quite a lot, mainly because the time scale is different. I'd say at least for my use case, 70% of the time is spent basically idling (internet browsing, writing a word doc, email, etc) or just not even using the computer at all. Especially for users who don't bother to turn off their computer, the 12W loss starts to add up pretty quick. I know its not easy to do, but I feel that because its not part of the spec for 80 plus, not very much effort is going into making improvements.
  • RaistlinZ - Wednesday, September 3, 2014 - link

    I think you expect too much. Anyone buying this is likely building a high-power overclocked rig, and wouldn't be spending much time at 5% power draw anyway. I also doubt the time, money, and effort into making PSU's 90%> efficient at 0-5% power draw is worth it from a manufacturing standpoint anyway.
  • fokka - Thursday, September 4, 2014 - link

    just because people are overclocking and gaming for a couple hours every day doesn't mean the close-to-idle times are negligable. people will still browse the web, write an email or watch a video or two.

    i'm not saying the inefficiencies at idle have to amount to a big loss compared to running a 1kw-pc at full load, but taken for itself it's still enough to power a complete low powered computer.

    i don't know about the engineering/physics side of things, but i'd say idle efficiency is still something manufacturers should look to improve.
  • Kutark - Sunday, September 14, 2014 - link

    The point is primarily that there is a minimum overhead that is needed to operate a power supply, and reducing that overhead is extremely difficult and in the end is not worth it. For example, if it takes say 12w of overhead, reducing that by 25% would basically put you at 9w. The return for the effort is simply not worth it (increased component costs, engineering/design costs, etc). Not many people would pay say a 10% price premium just to have the 5% load efficiency be 10% better so they can save basically save $6 a year in electricity costs.

    I've honestly never understood why people can't seem to pick their battles with these things. I always love when i would see people get into arguments here over a HDD that uses 8.2w instead of another one thats say 9.6w because its a 15% difference and thats massive! Well the reality is, its 1.4w. Now, in a corporate SAN environment where you might have say 500 of these drives in an array, yeah, 15% is a big deal. But to a home user who might have at most 2 of these drives in their computer, you're talking about $4/yr in electricity costs.

    Pick your battles.
  • dealcorn - Wednesday, September 3, 2014 - link

    If you use your over-clocking rig to browse the Internet you are wasting lots more than 12W. Get a petite, passively cooled Bay Trail desktop for browsing. Save the big rig for when you need the horsepower.
  • rarson - Sunday, September 21, 2014 - link

    Spend several hundred extra dollars to save a few bucks a year? That doesn't make any sense at all.
  • surt - Wednesday, September 3, 2014 - link

    Why does any power supply need to run a fan at 50w draw. Even if you're only 50% efficient at that load, you shouldn't need to actively cool 25w. If that's your overhead, just start the fan later.
  • Samus - Thursday, September 4, 2014 - link

    I want to chime in and agree with the OP here. Any PSU over 600W is going to be inherently inefficient at idle in many PC's.

    Below are my overclocked i5-4790 PC's individual power draw specifications taken with my Fluke multimeter, GW INSTEK GDS-122 oscilloscope using additive\deductive component elimination to calculate these measurements at idle within a reasonable margin of error using a PC Power & Cooling 750-QUAD 80-Plus PSU (which is really irrelevant since I am measuring current draw and using ohms law to convert into watts - the PSU has no bearing on the components individual power consumption.) However there is no reliable way to measure below 1 watt so the individual minimum component draw is such.

    Core i5 4690K @ 4500MHz 1.210v draws 12.8w at idle (FIVR reported via CoreTemp)
    2x8GB Crucial LPDDR3 @ 1600MHz 9-9-9 1.35v memory draws 3.2w at idle
    Samsung 840 Pro 256GB SSD 1.0w at idle
    Seagate 4TB 5900RPM 2.8w at idle
    WD 2TB 5200RPM (2.5") 1.7w at idle
    ASRock H87M-ITX measured via ATX connection 3.3+5.0+12.0 deduction 17.5w at idle
    EVGA nVidia Geforce 780Ti 3GB clocked 1025/7400 1.189v 22.8w at idle

    Total system draw before PSU efficiency loss is 62 watts. Since my PSU is only 75% efficient at 5-10% load, like most PSU's, my total system idle measured at the wall (with a somewhat accurate kill-a-watt) is 85 watts.

    However, I need a 750-watt PSU as my load power consumption can surprisingly eclipse 600-watts at full CPU + GPU load and I want to remain below the 80% load barrier where the PSU lifespan is shortened, temperatures and noise escalate and efficiency can REALLY take a dive.

    I think more attention needs to be taken with PSU efficiency at low idle state. There are various ways to do this, the most practical implementation being a dual stage power delivery circuit for different loads. Basically it would be a switching PSU inside a switching PSU, and it wouldn't be very expensive to produce because the first stage (lets say 0-100w) would be a very basic CLASS V, then there would be a voltage regulator and relay system that switches to the next stage with a supercap to isolate any voltage drop while switching.

    I'm surprised nobody has done this yet. Should I patent it?

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