Cant you just stick your PC in low power usage mode and turn off the monitor and download straight to it?
I have my fans on low (locked 42%) GPU idles at 210mhz, monitor turns off after 20 mins, SSDs use minimal power. My 5800X3d idles at 3600Mhz but im sure you can enalbe a low power mode something like C1 state.
Probably left something on CPU wise when I was changing settings years ago
Seems much easier to sort your main problem of higher power use on your PC when idle/just downloading than use another device and copy from one to another