I recently Upgraded my GPU from a 3070 to a 3080 and I already had a 750w PSU which is the recommended minimum by Nvidia. My PC would start crashing once or twice a day or my monitor would shut down once or twice a day and say it was not receiving a signal. So I replaced the EVGA gold 750w with a EVGA Gold 850w and after a week I have not had any problems. So judging from my own experience I would say that a 850w PSU is the minimum and I wish I had bought the 1000w for more head room or future upgrades. I always thought for the most part that if you PSU did not have the power, your PC woudn't boot.