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.
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Yeah, 230VAC is the key if you want to do something more than just a few units.  I have a 100A main with a 60A feed to a subpanel.  On that subpanel I have all of my mining and networking equipment as well as the lighting and HVAC for the room housing it all.  Right now I'm running 6xL3+, 4xL3++, and 8xA4+ along with a Z9 Mini and about 5ksol worth of GPU's spread over two PCs.  All of that equipment is running at 230VAC with no issues.  However, before I finished the room, I was constantly doing a fine balancing act with everything on 120VAC!