This is the foundation of your computer. No other single component endures the stresses that your power supply is subjected to. It can make or break the best systems when it does what it is designed to do. I never take my PSU for granted. I typically perform the calculations of the total watts required for a system before I purchase one and double that value loosely. For example on my 3900x based build the calculations without overclock, were 105W nominal for the CPU, 250W for the Radeon 5700XT GPU, I added another 50W for all of the other components. I have 3 NVMe drives in that computer. So the rough out was 450W bare minimum without overclocking to allow a bit of margin. I used an 860W Platinum rated PSU. Some ask me why I go nearly double. I often overclock my CPU, and my GPU and I tend to put a lot of fans inside my cases to keep them nice and cool even during the summer months in 90 degree temps. I also feel very confident that if I upgrade that system to a more robust GPU such as an Nvidia RTX 3080ti or the Radeon equivalent (yes I know this is a dream yet to materialize) that my PSU will handle the upgrade without a need for replacing it with a higher wattage unit in the near term future. A power supply will drop its ability to supply power over time due to the capacitors aging and drying up. This occurs with all power supplies even the very expensive ones. At the 5 year mark it MIGHT be as low as 50% of the rated value if it ever really was what the rated value suggests. If you have a really old power supply in a system that has had odd unexplained errors sporadically spend the money to buy a new one. In the 1980s I used to perform Hi POT tests on PSUs. I put them into a 3″ thick steel box for the testing and ran them up to 400VAC and 1.4x the Rated wattage dc. Someone once said that was overkill until one exploded during my testing and threw bits of metal through that 3″ thick steel. Thankfully I was outside waiting for the test to complete. No one was injured. I had a nice 8″ thick box on my test bench the very next day. Thank you Sam. I still left the lab during the Hi POT testing process, with the lab door locked closed.
Some of the Power Supplies I currently have in service in my systems.