What device can you recommend? I am not quite sure were the journey will go, but good recommendations are worthy.

Well the maximum size of an M-Disc Blu-ray is 100GB so I would have to write 10-30 of them… that would be pretty annoying 😅

Its around 30 cent currently cause I have a good contract.

During summer everything is fine cause my photovoltaic system produces almost all of the energy needed.

Have to go more detailed into planning there. Maybe a good Gold+ is the key here.

The cost will be at about 400 euros with a Celeron CPU, if the PSU is not 200 Euros alone :D

I aim for maximum efficiency as electricity is pretty expensive in Europe and a replacement for my Zimaboard, which will be used for testing then, because I want to switch from my old Synology to TrueNAS Scale.

The goal is to get an idle power draw of 10-20W (HDDs excluded)