I found  on LinusTechTips forum:

The EVGA G2 lineup is considered by many to be very high quality, the P2 considered fantastic, but the latest testing by professional reviewers shows that some or perhaps all of these units have a serious flaw that won't harm the PSU but could harm your other hardware. It's important to explain the concepts before anything. Very few reviewers test for this stuff - Aris, who does power supply reviews on Tomshardware and Techpowerup, very recently started a new test. This new test shows that many units have newly revealed flaws, and this problem exists with the EVGA G2 and P2 lineup. The EVGA G2 series is a direct copy of the Superflower Leadex Gold series. The EVGA P2 series is a direct copy of the Superflower Leadex Platinum series.
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Old Hold-Up Time Tests

In the past, most power supply reviewers would test "hold-up time" as the amount of time from when there is AC loss (i.e. power outage) to when the unit shuts off, while under full load. For example, if a power supply is under 100% load and there is a power outage, if it takes 20ms for the power supply to shut off, it would be defined as having a hold-up time of 20ms. However, this is not an actual test with what hold-up time really is, and new tests reveal new realities. The old hold-up time tests are not in exact accordance with the definition of hold-up time.

Hold-Up Time

Hold-up time is defined as the time period from when there is AC loss to when a voltage goes below ATX specification. The ATX specification for the 12V rail is from 11.4V to 12.6V. So if there is AC loss and it takes a power supply 20ms until its 12V voltage gets down to 11.4V, then 20ms is the hold-up time. Some people incorrectly define hold-up time as the time between AC loss and when the power supply shuts off. This is incorrect; a power supply may actually shut itself off after hold-up time. Hold-up time is strictly the amount of time from AC loss until a voltage goes out of specification.

AC_LOSS to PWR_OK_OFF

When there is AC loss, the voltage outputs of the power supply begin to drop to lower numbers. It is the job of the circuitry of the power supply to detect this and shut off the unit before the voltages go below the ATX specification. Basically, under-voltage protection. Before any of those voltages go out of specification, the power supply is supposed to cut the PWR_OK signal. The PWR_OK signal is a cable in the main 24-pin ATX cable used to communicate with the motherboard. When on, it's telling the motherboard that its voltages are all safe. When the PWR_OK signal is cut, circuitry is supposed to shut off the power supply as fast as possible so the voltages don't go out of specification.

The latest testing methods in renowned power supply reviews are AC_LOSS to PWR_OK tests. This tests the duration of time it takes from there being AC loss to the computer dropping the PWR_OK signal. So, for example, if there is a power outage, your computer is under full load, and your power supply has an AC_LOSS to PWR_OK time of 18ms, then in 18ms your power supply will tell your motherboard, "Hey! Voltages are about to get low. Better shut me off now." And then the unit will be shut down quite rapidly once the PWR_OK signal is dropped.

There is a catch though: some power supply units drop the PWR_OK signal after the voltages go out of specification. This means when there is AC_LOSS, the power supply will continue providing the computer with energy as those voltages go deeper and deeper below the ATX specification. Once it gets to a certain low point, then it'll cut the PWR_OK signal, after harm has already been done. In a way, this is a cheating method used by power supply manufacturers to do well on old hold-up time tests that check the duration of AC_LOSS to PSU shutdown time. This cheating method is also dangerous.

EVGA G2 550 Flaw

The EVGA 550 G2 has this exact flaw. It drops the PWR_OK signal at 10.8V. This information can be found at the Tomshardware Superflower Leadex Gold 550 review here: 

"The hold-up time tests don't go well. Not only is the measured hold-up less than 16ms (the ATX spec's minimum), but the Power_OK signal drops after, and not before, the PSU's rails go out of spec. This means that your motherboard gets a false power-good signal from the PSU. Indeed, we measured the +12V rail floating at around 10.8V when Power_OK dropped to zero. This is a very low voltage level that applies lots of stress to the voltage regulators of components fed by +12V.

In a high-end PSU like this one, we didn't expect such nasty behavior. We have to admit that we're very disappointed by Super Flower's decision to drop the power-good signal so late, which is probably done to give the false impression that the hold-up time lasts longer. By the end of our review, this is going to cost to this PSU a lot of performance points. Whereas it might have received an award for performance, there's no way it will now."

Some of you may be thinking, "Oh, it's just 10.8V, no big deal." No, this is a big deal. Power supply experts like Aris (who did the above review) say it is a serious matter, as well as the experts on the Jonnyguru forums. It is a serious issue, and the EVGA 550 G2 should not be purchased because of it, especially in areas where there are frequent power outages.

It is important to note that Aris did do a review on the EVGA 550 G2 here, but that was before these new tests came about.

EVGA P2 Series Assumed Flaw

Most likely, the entire EVGA P2 lineup has the same issue, but right now it is merely speculation (but a pretty good one). The Superflower Leadex Platinum 550 review here: 

This review was before the PWR_OK to AC_LOSS tests. Hold-up time was tested to be 13.8ms. That is below the ATX specification. There is no doubt in my mind that it probably drops the PWR_OK signal at 10.8V just like the EVGA 550 G2, in order to "cheat" and get good hold-up times on the old hold-up time tests.

EVGA T2 is Safe

The EVGA Titanium lineup has been tested and does not have this issue.

EVGA G2: Rest of Lineup

As of now, the non-550W versions of the EVGA G2 lineup may have these issues, but we cannot know for sure. Power supply experts are pretty confident the rest of the G2 lineup does have this problem, which is very important.

What to do Now?

Realize that sometimes units we think are incredible really are not. Everybody likes to go around forums talking about how fantastic the EVGA G2 lineup is, but with this problem, how can it be? It shouldn't make any high tier on any list, because Superflower cheats to get good hold-up time on old tests, and sets far too low under-voltage protection values. It is a serious matter, because the VRMs of all your hardware can be seriously affected by such a low voltage, 10.8V. There is a reason the ATX specification exists. 10.8V is two times out of the specification.



Small problem should only have people who will use PSU at 100% load like bitcoin miners?

In future if I buy Ryzen 7 - Zen2 + RX Vega 56 I should be around 50% of my PSU load. If during heavy gaming with that spec I have power outage there won`t be any problems, any fried components?

Is this "problem" only in these premium PSU level - it has bad reponse time in that level, comparing to middle range PSU level EVGA has better response time than most middle range PSU?
 
Mostly before I buy something I always look amazon and newegg reviews and Evga has really great users reviews, havent`t found anything of fried - destroyed components.
 
I bought Evga G2 850W last year. Because it is overkill for my setup (more futureproof) and it has 10 year warranty I will have it minimum for the next 10 years. Should I be worried because of this problem? I don`t want that this to cause any damage to my components....
 

Why can't mfg just make a quality product instead of cheat to get good hold-up times.
 
What are the chances of damage happening from power loss?
 

It's nice to see Tomshardware raising the bar for hardware testing. I hope they do more tests on retail sourced hardware in the future. 
 
 

I would like to see them test this by causing power outages, see how many outages it takes to cause any damage. See if they can tell any symptoms due to the damage.
 
 

G2 is on market about 4 years. 
And for now we couldn't notice unusually higher number of people who complain.
I have P2 and about 10-15 times my building and buildings arround stayed without power.
I have no UPS and for now everything is fine. But my PSU is far stronger than I need and she work 24/7.
Next time I will buy 1000W T2 because I have Sleeve Cables for that profile.

the_Scarlet_one
It does specify under full load, so if the system isn’t under full load, which many people don’t run their system at 100% all the time, then it is unlikely to become an issue as they were stating.

I have a feeling the internet keyboard warriors are getting ready to slam reddit demanding EVGA give them each a brand new x299 5980xe and Titan Xp system to replace their z67 board that died from this exact reason they have no proof of.

This is not just some what random internet troll wrote just to hurt EVGA, it is written in reviews on Tom`s hardware. I quote Superflower Leadex Gold 550 review, G2 is based upon it:
 
"The hold-up time tests don't go well. Not only is the measured hold-up less than 16ms (the ATX spec's minimum), but the Power_OK signal drops after, and not before, the PSU's rails go out of spec. This means that your motherboard gets a false power-good signal from the PSU. Indeed, we measured the +12V rail floating at around 10.8V when Power_OK dropped to zero. This is a very low voltage level that applies lots of stress to the voltage regulators of components fed by +12V.
 
In a high-end PSU like this one, we didn't expect such nasty behavior. We have to admit that we're very disappointed by Super Flower's decision to drop the power-good signal so late, which is probably done to give the false impression that the hold-up time lasts longer. By the end of our review, this is going to cost to this PSU a lot of performance points. Whereas it might have received an award for performance, there's no way it will now."
 
I am not PSU expert, I just wanted to be sure that my G2 850W doesn`t have this problem. Even if some models of G2 series have this problem I think that motherboards are not too sensitive that will affect them. To bad that Tom`s hardware reviewed only one G2 model with this new type of  hold up time test.
 
But regarding positive Amazon and Newegg reviews (nobody mention this problem as far as I seen) I think that this shouldn`t be a big problem unless you have very often power brownouts 

the_Scarlet_one
I have multiple G2 power supplies and frequently had sudden power loss in Japan, Korea, and Ocassionally where I am now, but never had an issue. I feel this issue would have very little affects on the average user, since the average user isn’t running thier system at 100%.

If the power supply were overvolting and causing issues, I could see it as a major concern, but this sounds like less of a problem than one article and one tested psu.

Also, super flower would be the target, as evga does not, in any way, make power supplies. They purchase and rebrand as mentioned in the article, so it would only be evga going after superflower to back their own customers.

Also, evga offers amazing warranty service, and if users can prove the evga labeled hardware caused the problem, they will help the customer, so I have no concern.

My jab at the internet warriors still stands, as people that have no idea what could actually happen will be screaming bloody murder more than likely. That is how reddit works. Take a small issue and turn it into something it never was.

EVGA would be the target, it's evga name on the product. The OEM designs the unit to evga specifications don't they?
 
I don't know how easy it would be for consumers to tell 100% that the power supply was the cause for mobo, cpu or gpu messing up. When you send a product in for warranty service, they never tell you what caused the hardware to fail, unless it has physical damage.
 
If a review website has all the expensive machines to test for stuff like that, i wouldn't consider them to be internet warriors. I wish they would do some testing to see if they can cause any damage to happen.  Does it take 10 or more power issues within a short period of time or what.
 
 

MSim
EVGA would be the target, it's evga name on the product. The OEM designs the unit to evga specifications don't they?
 
I don't know how easy it would be for consumers to tell 100% that the power supply was the cause for mobo, cpu or gpu messing up. When you send a product in for warranty service, they never tell you what caused the hardware to fail, unless it has physical damage.
 
If a review website has all the expensive machines to test for stuff like that, i wouldn't consider them to be internet warriors. I wish they would do some testing to see if they can cause any damage to happen.  Does it take 10 or more power issues within a short period of time or what.
 

I totally agree with you. Even if this problem can cause some damage PSU will survive but users will blame MBO, HDD or something other, they will not presumme that this is PSU fault.
 
From some other forum I found this:
 
"There are two things to watch out for:

 
- how long can the capacitors keep the PSU running in safe voltages, voltage vs time
 
- when does the PSU send power off signals so that the electronics can safely stop, AC_LOSS to PWR_OK, does it do it soon enough before the voltages drop too low

In the end you need both to be alright but some reviewers test only the signal, ignoring voltages, LOL, yeah, that bad review testing. Maybe some actually check for the voltages but not many. Most just skip testing this altogether because laziness, lack of knowledge or equipment.

Ideally you would have a plot of all voltages coming from the PSU, +AC, +signals.

The linked JG post goes into speculating the various G2 versions, 850 G2 doesn't have the signal so huge as 750 and 650. So the signal should drop soon enough before the voltages go too low.

I have had no problem with my 850 G2, but I also don't run it anywhere near it's capacity. Outages happen during extreme weather, especially on a first day. Too hot, too cold, too windy, stupid power company cuts off remote areas when ever they need unfortunately, sometimes hell it's just a typical sunny day or they schedule some maintenance. 10 outages a year, I guess, it's possible, sometimes several at once when they flip it on and off.

mmonnin: because a decent UPS costs 25% price of the whole PC even. And they don't last either, the batteries need to be replaced every 2 years unless all you really want is just a 5min protection. And a cheap UPS might just do more harm than good. All UPS can protect against is some small level of under and over voltage, that's all. Most PSUs are fine with that on their own, your PC just shutsdown.

Sure we would all like to have solar panels on roof and a huge battery pack for the whole house, but not all of us live in a rich California with endless sun."
 
I am glad to find more expert opinions who thinks that G2 850 shouldn`t have this problem. I don`t say that this is a big deal but I will sleep more peacefully during stormy nights.