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.
Drives only consume power on reads and writes, if your NAS spins them down as it should (and apparently QNAP *doesn’t, which I didn’t know).
As per my other comment - 8 drives or 1 drive, same idle power for desktop hardware. My actual NAS uses about 1/8 the power at idle for 5 drives.