I use a Pi 4B as a 24/7 home server in a country where domestic electricity is expensive (and worsening).

Each Pi release is more powerful, but uses more energy. I found the Pi 4B to be the sweet spot for me, because it is the earliest model to support USB booting, gigabit Ethernet, and offer > 1GB RAM.

Perhaps a used one would fit your purposes and budget?

I currently use it to run PiHole, serve media via SMB, host Postgres & Redis, and run some custom written Dockerized apps. Home Assistant to possibly follow, too. The current load seems reasonable in htop, but I haven’t looked into burst scenarios.