I think you simply can't predict any number without really measuring it.

Ryzen + GPU + 1h of gaming, but 3 screens attached.

still a "desktop computer" - stuff in the browser can spike GPU wattage, but I don't think it will be meaningfully different over several hours of true idle..

My problem is more like: I could measure that, but I'd have to recable everything to have the power meter behind the power strip with just PC + screens... which I will probably do at some point, but it involves redoing 50% of the cables in this room.

During training it’s running at around 410. But yeah idling at 450 would be pretty crazy.