I have been using an old PC as NAS and running docker containers (Immich, Nextcloud, paperless-ngx etc.). I got 5 3.5" HDD disks and a Nvme. Even on idle, I am consuming 50-60w. A friend of mine is selling a Qnap NAS which is a dedicated machine and probably consumes less power, although I don’t know if it’s worth it.
A big portion of that is caused by the drives, so you’d have to compare the empty QNAP vs your empty machine. Also, depending on which NAS appliance, check that the CPU is actually powerful enough to run all your services.