Is it possible to use the PC Power Supply at 100% (Question to Overlockers, GURU)?

Question

Power Supply

There is a PC with 300W. Motherboard with built-in Intel vidyuhi of yesteryear.
Wanted to update a bit. Looked at NIX.ru, the desired vidyuha has 180W. Yes, and in the same range they also have 180W.
I summed up the power of all components and found out that:
CPU - 75W.
MB - 20W.
3x HDD - 3*6W= 18
WiFi PCIe- ~10W.
-------- = 120 W
I buy a 180 W video camera.
Total = ~ 300W.
---------
Actually, this is not my PC. And distant relatives. They categorically do not want to buy another case.
Is it possible to use the PSU at 100%?
-On the other hand, a 180W video card will not always consume, but only in highly loaded games.
-And it is also worth understanding that the power on the PSU is indicated with the load rating. But in fact, the manufacturer must give a guarantee and be responsible for his words.
The opinions of everyone who wants to troll on the topic: "If I were in your place, then I would buy a new PSU with a margin of 800W." PLEASE DO NOT WRITE. I ask you to write specifically on the figures and on the facts and personal experience.

Answer 1

In addition to the total power, you need to check the consumption of the individual lines. For example, a card with a processor on the 12V line consumes 255W, and the PSU gives only 240W on it - then it definitely won't be enough.
PSUs from little-known manufacturers, as a rule, do not pull 100% power - a transistor or diode can overheat and burn out, and a branded supply of 20-30 percent will not hurt.
Look at a video card with lower consumption or change the PSU, it is not necessary to change the entire case.

Answer 2

It will work somehow, but there is a possibility of unstable operation in a loaded state. What prevents you from buying a more powerful PSU and not changing the case?

Answer 3

Platinum or titanium - yes.
Below the PSU class - it may not draw out the stability of supplying a stable voltage.

Answer 4

It’s possible, but not for long, we didn’t get accustomed to keep the stemnik in the refrigerator and clean the dust every six months inside.