A:Answer Typically the standard is to calculate how much power your computer can consume if running full tilt and then double that and that is the PSU you need. I personally think that's a bit conservative. It has been my experience that when using a good PSU made by a good company, whatever your max current draw could be, multiply that by 1.5 and that should be suffice.
That said, a 455 watt system running on a 500 watt PSU is IMO not a good idea. Running your PSU that close to the limit will absolutely reduce your PSU life and increases the risk of catastrophic PSU failure that could cause damage to your system(MB, Peripherals) and could potentially fail to such an extent that it could cause a fire. So my advice to you would be to upgrade to at least a 650 watt or 750 watt.
All that said, my current system has a 500 watt PSU and I have a Ryzen 5 1600X and two RTX 2060 Supers and my total power draw from the wall outlet is about 400 watts when running both GPUs at 100% and the CPU 50-80%. I do need to upgrade my PSU and it's on my list. But until I do, I am limiting how long I run both GPUs at the same time.
I hope that helps.
