For sale? Probably. For use? It's the same hashrate/power consumption per chip, the mini will continue to be profitable at the same ratio as the bigger guys, just less on a day to day level.
Also Z9 mini is realistically the only ASIC miner for mining at home without any special investment in electrical installation (even if you a have a few of them). The noise level is border line tolerable and it is using not much more power than GTX1080Ti (with the price of second batch with coupon, comparable as well)
Not at all, pretty much all Bitmain miners are usable at home without any electrical mods (provided your house doesn't have pre-60s wiring still); any 20amp circuit will easily suffice, and most of them run fine on a 15amp line. That said, ALL miners are more efficient on a 220v line, and the A3 and S9 both require their own dedicated lines (I assume the Z9 biggie does as well)...
Make sure to use a psu that will function on a 110v line at the wattage you need.
You misunderstood me or I should have said that these Z9 mini miners are in addition to the existing GPU mining rigs (2.5kW). Do not forget that a house has lots of appliances and some of them also take up to 1.8 KW in peak. Temperatures this Summer are high and I had to add a portable AC (in addition to central air). I could not add a S9 without adding 220V installation.
A 20amp 110v line provides 220W. by the 80% rule, that means a constant draw of 1.76kW is perfectly acceptable, you just need it to be a dedicated line. (this is an example; most of the single phase lines in my house tend towards 120v, so their ceiling is higher).
I'm not saying 220-250v isn't preferable, it is, for numerous reasons (more efficient as well), just saying I ran all my miners, including my A3, on 110v lines until I set up my subpanel. You just have to make sure you're not putting high draw gear on busy circuits and not hitting the max for the house as a whole. But again, if you're going to add lines anyway, you might as well put in 220v ones.