Corsair HX750i 80 PLUS Platinum PSU Review

Technically, the efficiency of a PSU is unrelated to its wattage. Some of the most powerful PSUs sport the best efficiency, though. Then again, few people truly need 1000W or more, and even fewer are willing to pay a premium for output levels they have no use for.

Also consider the fact that when you under-utilize a high-output PSU, you operate it at a power level where its efficiency is less than the advertised number. Thus, what you really need is a lower-wattage PSU - and there's a good chance that power supply is going to be adorned by an 80 PLUS Gold rating or lower. Even in the mid-range of the wattage spectrum, Platinum-class products are scarce.

The entry-level model's look and feel are excellent. It's a well-built PSU with nicely chamfered edges. All of the cables are modular and flat, which can improve routing and airflow. You get access to two CPU cables, six 6+2 auxiliary connectors, 12 SATA plugs, eight Molex connectors and two floppy drive plugs. All of the cable lengths are generous except, perhaps, the SATA cables, which we prefer to be longer than the 33.5” we measured. At least you have 12 of them, qualifying the HX750i for use in a storage server.

Corsair's spec sheet mentions a single +12V rail able to deliver up to 62.5A. But for system builders who prefer multi-rail supplies, you can configure the PSU to operate that way via Corsair's software (for our testing, we stuck with a single-rail arrangement). Since 62.5A * 12V equals 750W, 100% of the PSU’s nominal power can be drawn from the 12V rail.

A seven-year warranty exceeds the industry average and may be the deciding factor for enthusiasts on the fence, faced with many compelling options.

Corsair HX750i
AC Input100-240V, 50-60Hz
DC Output+3.3V+5V+12V (#1)+12V (#2)+12V (#3)+12V (#4)-12V+5Vsb
25A25A62.5AN/AN/AN/A0.8A3A
Individual Output     9.6W15W
Rail UtilizationSysSysCPU & VGA
Combined Output150W750W
Total Continuous Output750W
Peak OutputN/A

Efficiency According To The 80 PLUS Spec

Efficiency In Typical Use Cases

So far, the Corsair PSU looks promising. But it still has to pass a series of stringent tests in our lab. Let’s recap the requirements of the 80 PLUS organization. A Platinum-grade PSU is required to achieve the following efficiency percentages at 110V: 90% efficiency at 20% load, 92% at 50% load and 89% at full load.

At low and high loads, the HX750i easily satisfies those efficiency requirements. However, at medium load, it runs into a minor issue. We calculated an efficiency of 91.96%, which is 0.04% less than the requirement. Then again, that's very close to 92%, and we're going to give it the benefit of the doubt. A second sample could show up on the other side of the cut-off. At very low loads, the HX750i’s efficiency gets worse, which is no big surprise in and of itself. But the other two PSUs we're working on do sport better numbers.

Corsair's ripple and noise values are exemplary. Further indications of this PSU’s quality are its low inrush current and long hold-up time.

Documentation claims that the HX750i PSU features "virtually silent" operation, meaning automatic, hybrid fan control. In other words, the fan only starts once a certain load or temperature is exceeded. Corsair says that under 300W, the PSU doesn't need its fan. And we found this claim to be true. When we ran at 40 and 200W loads, the HX750i was completely silent. When the fan does spin up, its sound level is quite subdued; 29.5 dB(A) is barely audible, even in quiet environments.

A Closer Look at the PCB

As we've come to expect Corsair has the HX750i built at CWT (Channel Well Technology), a contract manufacturer renowned for high quality. The input filter is split into two stages and sports a total of six Y capacitors, two X capacitors, two coils and a bridge. Like the electrolytic capacitors on the secondary side, the primary capacitor is made by Nippon Chemi-Con. The secondary-side polymer capacitors are manufactured by Apaq and Enesol. The soldering quality of the main PCB is top notch, while the soldering quality of the auxiliary PCBs is good (though not perfect).

Conclusion

In the days to come, you'll see Corsair’s HX750i challenge two somewhat dated models from FSP and SeaSonic. Is the fight fair? We think so. After all, the three candidates are 80 PLUS Platinum-rated according to their spec sheets, and they offer comparable outputs.

The inspiration for our test, Corsair's HX750i, does manage to impress right out of the gate. Its manufacturing quality is among the best we've seen, inside and out, and its feature set is richest amongst the trio of ultra-efficient PSUs in our line-up. The two other models simply don’t offer as many connectors, nor do they include software-based monitoring and configuration. Our lab tests doesn't uncover any obvious flaws aside from a less-than-perfect efficiency measurement at 50% load. This is a fairly minor issue exhibited by all three contenders. Corsair's HX750i also does its business quietly, and in many cases even silently. As such, it earns a first-place finish, though it shares the honor with another PSU. You'll have to keep coming back to learn which other one excels.

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  • Amdlova
    I think i will pass the corsair products...
  • MasterMace
    I appreciate the article, but I'm a little lost on a few things.

    What temperatures were used in these testings? Were they hot tests? Cold Tests?
    The device's operating temperature claims up to 50C. Why wasn't this tested?
    What devices were used to test them?
    Efficiency was tested. What levels were the rails loaded to test this?
    Why weren't crossloads tested?
    You claim good hold-up time on this unit, but didn't put the results in your review, what is the hold-up time?
    You claim good inrush current, same thing as above, what is the inrush current amperage?
    If you're testing hold-up time, you're likely testing transient responses, why aren't those listed, or (if not) why aren't they tested?


    Just a few questions I came away with.
  • wabba
    my questions are at witch watt or temp does the fan turn on?
    claim is 300w and you test at 200w and 375w, i still dont have a answer from your test if the 300w claim is any good, and how about electrical noise? is there any at any load? my corsair ax 850 got coil whine like hiss noise at very low wattage, when i load a youtube video or read from the ssd.
  • thundervore
    As someone who own a few Corsair products that is integrated with Corsair Link I only have one question.

    Did you install the Corsair Link software on a Windows 8.X computer and get it to work without calling tech support or vising their forums? Bet you didn't, you failed to realize most customers buy the "I" products form Corsair because they want the Corsair Link integration with other Corsair Link products like a H100i.
  • Nintendork
    I still don't get why manufacturers can't realease PSU with plat/titanium rating aimed to low/medium power PC's. 250-300-350-400w would be awesome

    Many people buy high end cpu/gpus and run them @stock without overclock. A 4690+GTX970 PC should be taking less then 250w at full power. A 65w i5 + GTX760 less than 170w. AMD APU systems with the 7850 around 90-120w.
  • jshcastle
    Nintendork, I'm not sure where you are getting your figures, but all of the combinations you listed seemed to account only for the CPU/GPU at full load. You also need to calculate in the power needs of the motherboards, HDDs, fans, etc. that would be in each system. In actual use scenarios all of the components that you listed there combined with the remaining parts will pull quite a bit more that what you said. Regardless of that, it is generally ill-advised to build a system with a power supply that meets or exceeds the systems power requirements by only a small margin. What you end up with is a system that puts an overly excessive strain on the power supply, which will most of the time result in shortened lifespan and reduced reliability.
  • jshcastle
    Nintendork, I'm not sure where you are getting your figures, but all of the combinations you listed seemed to account only for the CPU/GPU at full load. You also need to calculate in the power needs of the motherboards, HDDs, fans, etc. that would be in each system. In actual use scenarios all of the components that you listed there combined with the remaining parts will pull quite a bit more that what you said. Regardless of that, it is generally ill-advised to build a system with a power supply that meets or exceeds the systems power requirements by only a small margin. What you end up with is a system that puts an overly excessive strain on the power supply, which will most of the time result in shortened lifespan and reduced reliability.
  • mamasan2000
    "But for system builders who prefer multi-rail supplies, you can configure the PSU to operate that way via Corsair's software (for our testing, we stuck with a single-rail arrangement)."

    Did you test the software? Would be interesting to know, especially since Corsair Link is VERY hit and miss. Not the best software company in other words.
    I just skimmed the article so sorry if it was mentioned.
  • MasterMace
    205977 said:
    I still don't get why manufacturers can't realease PSU with plat/titanium rating aimed to low/medium power PC's. 250-300-350-400w would be awesome Many people buy high end cpu/gpus and run them @stock without overclock. A 4690+GTX970 PC should be taking less then 250w at full power. A 65w i5 + GTX760 less than 170w. AMD APU systems with the 7850 around 90-120w.


    I don't know where you get your numbers, but they are wrong. According to XBitLabs, the i5-4690 pulls 172W in Linpack, according to Toms the GTX 970 peaks at 250W on the 12V oced, the i5 4690 at stock. I imagine at reference it would be less than 250, but you'll be hard pressed to find a stock review with peak power consumptions recorded. That's 422W on the 12v rail by themselves, not including the aforementioned rest of the computer. Considering you don't want to blow up your Power Supply, you do not want 422W to be the maximum output on your 12v rail. You'd need 44A on the 12v rail, and thus be looking at a 550W PSU.

    That being said, if your rig is using an i5 4690 and a GTX 970, you're overspending if you are looking at a Platinum PSU. $170 on a PSU when you spent $550 on your CPU+Graphics, and are looking at a $900-$1100 build is a bit out of whack.
  • Gundam x
    can it run sly gtx 970
  • raheel136
    ^Total system power consumption with a single 970 is 300watt and 970 sli will consume around 500watts... so this 750w psu is enough
  • MxMatrix
    About half a year ago I had issues with the HX750, predecessor of the i version. Sadly no i model was available then so I went for the EVGA equivalent. The LINK software that uses the i options and displays them, makes the devices tune able and regulates operation is a boon to me. I like quiet operations, but when power usage comes in I want the machine to respond properly and not from about 50 to 100 in one step (in sound production). The i option makes it possible to gradually increase fan speeds. And react pro-actively on sudden heat increases.

    Only drawbacK; you'll have to circumvent windows 8.1 to get is working, that's a bit too much for a lot of people.
  • sportfreak23
    Low-Power Efficiency??? This review just became a joke. So many features about the PSU weren't even mention and tested. When does the fan turn on? at what load? Even Johnny Guru gave it a perfect score beside value as its an expensive PSU but you get what you pay for. I still prefer the Ax lineup that is keeping 4 of my PC's running silent. Also not sure why people are suggesting 400w wouldn't be enough for a system running at stock. I'm running a seasonic plat 520w 4930k+780 overclocked and no troubles so far. Only reason you should consider more power on a PSU is to increase the threshold where the fan would remain silent under use.
  • InvalidError
    Unless your test equipment and methodology have better than 0.01% overall accuracy, 0.04% is too close to tolerances to call a pass or fail. You could probably cause results to change by more than that by wiggling connectors and cables.
  • beetlejuicegr
    there was a nice article about power consumption in tomshardware and it was pretty recent. What i personally learnt is that it is completely naive to count watts to decide for a PSU.
  • Jay Liu
    Too much gimmicks. I can get a Seasonic Platinum 1250W for less than the HX750i. What the hell do you need to control on a PSU anyway?

    These useless features are like their rainbow color LED lighting on mech keyboards, useless fluff. My friend's HX750 failed on day 1. I think getting PSUs to do what they're supposed to do is more important than upselling useless crap.
  • dovah-chan
    So many people confusing TDP with actual power consumption.