850W minimum, but honestly I'd go 1000W if your budget allows. These new GPUs can have pretty aggressive boost behavior and transient spikes. I'm running a similar setup with a Corsair HX1000 and it's been rock solid. Plus if you ever want to upgrade to a 5090 down the line, you're already covered. Don't cheap out on the PSU - it's the one component that can take everything else with it if it fails.

1000W PSU is recommended.

Get the Corsair RM1000e 2025.

For a Ryzen 7 9800X3D and RTX 5080, an 850W PSU is a good starting point. However, if you plan on overclocking, especially the GPU, a 1000W PSU offers more headroom and future-proofing. Ensure the PSU includes the new 12VHPWR cable for the 5080 to avoid adapter issues.