I mean... my old PC burns through 50-100W, even at idle and even without a bunch of spinning hard drives. My actual NAS barely breaks that under load with all bays full.

I could scrounge up enough SATA inputs on it to make for a decent NAS if I didn't care about that, and I could still run a few other services with the spare cycles, but... maybe not the best use of power.

I am genuinely considering turning it into a backup box I turn on under automation to run a backup and then turn off after completion. That's feasible and would do quite well, as opposed to paying for a dedicated backup unit.