Modern dell desktops (like 8th gen+) idle around 10W. Raspberry pi isn’t saving much
I had a Nuc 9 extreme with a 10gb SFP card in it.
It averaged 69w. The Mac Mini I replaced it with uses just under 5w.
A Mini is possible the worst bang for buck. Also, the horror that that is Desktop Docker can’t be over emphasised. I know there are better ways of using Docker on a Mac, but having got something working I can’t face rebuilding it.
I also have some Fujitsu office machine I picked up for $50 as my "I need to run some random task on a physical linux box" machine with an i5-7500 and it idles at 15W
OrbStack is my go-to when it comes to running docker on Mac. It also uses macOS native containerization APIs so containers will be a bit more performant than they would (at least use to) be on Docker Desktop.
Another good approach if you’re fine without a GUI or want to bring your own is just ‚brew install docker‘.
I’ve got it working, but compared to doing it in compose, it’s awful.
I've got an Optiplex with an i5 and two hard drives and that idles around 12W when idling.