Five Highly Efficient Power Supplies: 1200 W and Up

Corsair AX1500i

‘Does it contain a PC?’ was our first question after unpacking the Corsair AX1500i – its depth is a whopping 8.9”, which is comparable to some bare-bone PCs. In other words, please consider the depth of this PSU when choosing a computer case. The power cord of this PSU is specified for 16 A – while most power cords are 10 A models, that wouldn’t be sufficient for plugging this PSU into a 115 V circuit. Assuming that its efficiency is 100%, which even a Titanium-grade PSU can’t achieve, it would draw more than 13 A from a 115 V circuit at design power. By the same measure, the 10 A power cords of the Antec, Cooler Master, and Seasonic PSUs are out of spec on 115 V circuits. While the Enermax Platimax 1500 also came with a 10 A cord, we obtained the European 230 V-only model and, needless to say, only tested it on a 230 V line. Twice the voltage implies half the amps, thus the 10 A power cord is fine for 230 V circuits.

Material quality and workmanship are excellent, but this is true for all high-end power supplies. However, this power supply can differentiate itself with its high efficiency: 80 Plus Titanium – a first in our lab. At the time of writing, the website only lists 7 Titanium-grade PSUs: Six models from a company called ‘Super Flower’ and the Corsair AX1500i. We are curious how much more efficient the latter PSU is than the four Platinum-grade PSUs in our test. But let’s discuss its specs first. Its single 12 V rail can supply up to 125 A, 25% more than a single-rail 1200 W supply can muster. Single-rail PSUs have the advantage that you don’t need to plan how to balance the load across the rails. Like Cooler Master, Corsair encloses flat modular cables. The cables are more than sufficiently long, up to 31”. The number of connectors is quite impressive, even though ten PCIe connectors are not the most we have seen in this test. But 20 SATA power plugs and twelve Molex jacks certainly set a new record!

Swipe to scroll horizontally
AC Input100-240V, 50-60 Hz
DC Output+3.3V+5V+12V (#1)+12V (#2)+12V (#3)+12V (#4)-12V+5Vsb
30 A30 A125 An/an/an/a0.8 A3.5 A
Individual OutputRow 2 - Cell 1 Row 2 - Cell 2 32 ARow 2 - Cell 4 Row 2 - Cell 5 9.6 W17.5 W
Rail UtilizationSysSysCPU & VGA
Combined Output180 W1500 W
Total Continuous Output1500 W
Peak Output1650 W

Efficiency According to the 80 PLUS Spec

Efficiency for Typical Use Cases

Squeezing more and more efficiency from PSU components gets tougher and more expensive as the theoretical limit of 100% is approached. Currently, 80 Plus Titanium is the most demanding efficiency standard – its efficiency requirements at various load percentages are as follows: 10% load – 90%, 20% load – 92%, 50% load – 94 %, and 100% load – 90%. It is obvious that these numbers are not easy to achieve, and the Corsair PSU clearly struggles at medium loads: We measured 93.9%, but we attribute the missing 0.1% to measurement tolerances and don’t accuse Corsair of cheating, especially taking into account that the PSU exceeds all other requirements by at least 1 percentage point. At 10% load, the PSU achieves 90.7% efficiency, and at 85 W still 86.1% - the best results in this round-up test. As the load is reduced further, the Corsair PSU finally falls behind PSUs with lower wattage, but it consistently beats the 1500 W Enermax Platimax. But then again, low-power measurements are almost pointless for high-power PSUs. The hold-up time is more interesting, and the Corsair PSU sports more than 30 ms – outstanding. All other test results are within specs and not very exciting. However, we noted the exceptionally low ripple voltages – a rare occurrence in our lab. Kudos to Corsair!

Like the Cooler Master PSU and the Seasonic PSU, the AX1500i features hybrid fan control, but it cannot be disabled, hybrid mode is always active. The fan slowly begins to turn at approximately 600 W power draw. The key word here is ‘slowly’: You can almost count its revolutions. And it is also very quiet – 29.4 dB(A) is all but inaudible.

A Closer Look at the PCB

Corsair tasked Flextronics with building the AX1500i – Flextronics is perhaps the premium CMS (contract manufacturing service). For a pricey top-end product this makes totally sense, and the outstanding soldering quality reflects this choice. However, the components come from a potpourri of manufacturers: While all primary-side capacitors are made by Nippon Chemi-Con, the secondary-side capacitors were manufactured by Nippon Chemi-Con, Nichicon and Rubycon, and the polymer capacitors by CapXon and G-Luxon - second tier manufacturers. Then again, we don’t worry about the polymer capacitors too much.

  • blackmagnum
    I respect mother earth and her well-being; I will never hurt her by accepting these gluttonous monstrosities in my gaming builds. Low budget/ low power/ high efficiency FTW!
  • Alex Kelly
    Where is the EVGA Supernova P2 series? Would have been nice to see it included. :)
  • kevith
    Schön, dass Ihr auch deutsche artikeln jetzt schreibt. Das hätte ich mich nie gedacht. Aber was mit alle die amerikanischen leser? Die kann bestimmt kein deutsch?
  • damric
    Much better PSU review than usual for THW.

    However, none of these PSUs are as interesting as the SF Leadex.
  • Alex Kelly
    13853559 said:
    Much better PSU review than usual for THW.

    However, none of these PSUs are as interesting as the SF Leadex.

    Agreed! That's why I wanted to see the P2 here.
  • nikolajj

    Well, you don't seem to understand fully.
    They don't really consume more power than the connected hardware demands. On the other hand, they have an amazing efficiency rating, meaning that they use a minimum of power, and are therefore better for the planet. ;)
  • mapesdhs
    Pity the Thermaltake Toughpower XT Gold 1475W wasn't included, I've obtained
    half a dozen of them recently, excellent PSUs.


  • TheMentalist
    Cooler Master really stepped up their quality in PSU's, can't ignore that.
  • lp231
    I still like the interior of my Antec TruePower Quattro 850w. Massive heatsinks!
    About that Antec 1300w PSU, according to their site, it says that has a "20+8-pin MBU socket for the needs of tomorrow."
    Do you guys have any info on this?
  • majormajormajormajor
    "At the time of writing, the website only lists 7 Titanium-grade PSUs: Six models from a company called ‘Super Flower’ and the Corsair AX1500i"

    Wow, way to discredit yourself completely. You're reviewing power supplies and you've never heard of Super Flower?