Cold Test Results (Room Temperature)

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.

The new Corsair HX850 falls a little short regarding its 80Plus Platinum certification, failing to achieve >94% efficiency at 50% load with an input voltage of 230 VAC. This result however does not mean that the unit’s certifications are false, just that it received its efficiency rating with an input voltage of 110 VAC, under which the 80Plus directive is slightly more lenient. Also note that our ambient temperature is a little higher than the 25 °C recommended by the directive. Despite that, the HX850 has a very high average efficiency of 92.7% within its nominal load range (20% to 100% of the unit's capacity) and gave us fairly good efficiency readings under low loads.

The high efficiency of the Corsair HX850 allows the thermally controlled fan to stay inactive for a very large portion of the load range when the unit is operating in room temperature. Our test sample reached an output of nearly 400 Watts before the fan started to spin. The fan was relatively quiet thorough the entirety of our room temperature testing, reaching high noise figures only when very heavily loaded.

External Inspection, Package and Contents Hot Box Test Results
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  • DanNeely - Tuesday, October 24, 2017 - link

    I think I found an error. The table lists only 1 4+4 pin CPU power cable. Corsair lists 2 (as does newegg). In addition there're 5 12v connector ports on the PSU, 2 CPU and 3 GPU cables would fill this out nicely. And with the proliferation of new high end boards expecting 8+4 or 8+8 CPU power connections only 1 would be a poor fit for the enthusiast market.
  • DanNeely - Tuesday, October 24, 2017 - link

    I also have a question. Do the PCIe cables split into a Y with 2 independent wire bundles at the PSU or are the two connectors daisy chained on a single wire bundle.

    I'm asking because with the proliferation of single 8 pin power connection GPUs the daisy chain topology makes cable management a lot easier since you don't have to hide an entire 18 or 24" wire bundle. Having to do so sorta defeats the purpose of modular design IMO.
  • jonnyGURU - Monday, October 30, 2017 - link

    All of the Corsair PSUs that use Type 3 or Type 4 cables use "pig tail" cables that put two PCIe connectors on one cable.
  • TEAMSWITCHER - Tuesday, October 24, 2017 - link

    That 10 year warranty is a nice feature.
  • Golgatha777 - Tuesday, October 24, 2017 - link

    Hopefully you'll never need it. My HX850 has been going strong through multi-gpu and overclocked CPU setups since Sept 2011. Currently it's got a light load of an overclocked i7-5820k and GTX 1080 ti.
  • DanNeely - Tuesday, October 24, 2017 - link

    Good PSUs tend to be rather reliable so probably not. Over the last 15 years I've gotten about 35-40 years or so of run time over 7 or 8 different PSUs in my personal computers. 0 failures with anything electrical. 1 mechanical fault from a modular connector plug that somehow got smashed back into the body of the PSU and no longer made good electrical contact with the cable plugged into it.

    Attrition in models over the years has been mostly due to changing standards. 3.3/5v vs 12v focused models. Sata plugs instead of molex. The CPU connector going from 4 pins to 8 pins (and to twin connectors whenever I build a new high end box). PCIe power plugs being added, increasing in number and getting 8 pin versions. At the bottom end I think I retired a basic 80+ model after working out that over the boxes lifespan a more efficient one would pay for itself.
  • just4U - Wednesday, October 25, 2017 - link


    Your's was made by Seasonic, CWT has never been quite as good. The warranty is nice though.
  • jonnyGURU - Monday, October 30, 2017 - link

    They leap frog each other. Seasonic stalled for a while, allowing CWT to put out better products for a number of partners. But with the Prime line, Seasonic has jumped back ahead. Still... I'd take a newer CWT over an older Seasonic.
  • StevoLincolnite - Wednesday, October 25, 2017 - link

    Got an almost 12 year old HX620 humming along fine in a Core 2 Quad QX9770 @ 3.8ghz + 8GB DDR2 + Radeon 7970 rig. Still plays the latest games at 1080P every day.

    Only PSU's I will buy are Corsair... Another company would need to prove they have the reliability+features+warranty and beat Corsair on price for me to even remotely consider them.
  • BurntMyBacon - Wednesday, October 25, 2017 - link


    Corsair (HX or AX series only) is one of only three PSU manufacturers I consider for builds as well. I have seen good reliability out of them with their HX and AX series supplies. Judging by your criteria, I propose considering Seasonic for your short list as well. I've installed several of their old X-Series power supplies that are about the same age as your H620 and still going strong. Two of them are 24-7 operators (Folding@home or gaming) with multiple GPUs. The irony is Corsair used Seasonic's platform for a lot of their earlier HX and AX series PSUs so your HX620 may in fact be a Seasonic platform. Their prime series has some of the best performance in the industry (Similar to Corsairs Flextronics based AX1200/AX1500) and they come with a 12 year warranty. About the only thing missing (for those who can use it) is a Corsair Link equivalent. Pricing is competitive with Corsairs HX and AX series supplies and the better deal usually comes down to which one is on sale.

    Warranty Upgrade:

    Article to check it out:

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