Here's the first mining rig I bought. It's an antminer 7-ln. The thing draws 740 watts at my wall. It has a hashrate of 2.7TH/s, which pays be somewhere around .0032-0.0036 btc/day. It's about $2.50 a day right now. I live in New England and my electricity is pretty expensive at $0.19/KWh. So, running it costs me .74x24x.19= $3.37/day.
Now a sane person would look at that and say "Hey dipshit. You're losing money!" That's true, but as it turns out I blog from my office in my attic, which is unheated. I need to run a space heater. The space heater uses about 640 watts. If I can replace my spaceheater with this antminer, which I did, and keep the place warm enough to not feel like a water protector getting hosed down in sub zero temperature by the amazing violent and truly unamerican North Dakota state police acting as militarized oil contractors then it's a good deal. Effectively, it's costs me 100 watts to make bitcoin and I would have used the other 600 watts anyways, but it would have just cost me money rather than make me some too.
So, while overall I'm down on money for this thing because I need the heat I think of it like a thing that costs 100 watts or something that costs me $0.45 to make $2.50. So, at least for the winter it's a good deal. I don't think I would use more than one, but I'm glad I have this thing chugging away.
I have the proceeds going going to steem right now. So, I can also put that investment in the entertainment category.