Well. Running your machine to do inference will utilize more than 50W sustained load, I'd say more than double that. Plus electricity is more expensive here (but granted, I do have solar panels). Plus don't forget to factor in that your hardware will age faster.

I'd say it's not worth it. But the idea is cool.

Their estimate is based on significantly lower consumption when under load. E.g. 25W for an M4 Pro mac mini. I have no idea if that’s realistic - but the m4s are supposedly pretty efficient (https://www.jeffgeerling.com/blog/2024/m4-mac-minis-efficien...)