I have similar issue since ue5 (rtx 3060), im still trying to figure out. Now in 5.2.
I tried everything, people say lumen is costly, but like even after disabling all lumen, setting dx11, forward renderer, all scalability to low, tsr to 1080p, cookin in shipping mode apparently makes little difference, still u get 60 fps (not talking about fps cap here) on EMPTY black scene but the gpu wattage is like +110 watts. thats ridiculous high. Its around the same wattage i get for a small scene with lumen.
It makes no sense honestly and it feels like a bug. I already tried everything u can possible imagine. Even looked at unreals rendering thread code. I still think theres some sort of hidden issue nobody rly noticed.
For instance, when trace profiling with ue insights if u set maxfps to 30 it shows the rendering thread fps goes nuts +120fps, the game thread keeps at 30, which is rly weird, since all internal stats show rendering at 30.