How loud are these things? Also looks like if you have 20amp circuits you can only have 3 units per circuit assuming you don't have a ton of other stuff already plugged in! Then maybe just 2. So much power use...
Avalon unit use 620W @ 120V so it draw 5.17amp/unit. It's not recommended to load a circuit over 80% capacity. So 80% of 20amp = 16amp. 3 units @ 5.17amp = 15.51amp. No problem with 3 units.
At 220V and 600W (I don't have the exact spec but the unit should be a little more efficient) it draw 2.73amp/unit so it's possible to connect 5-6 units (13.9-16.38amp) using the same wire gauge.
It might be a good idea for some user to hire an electrician to install a custom circuit.
Disclaimer : I'm not an electrician so double check these numbers with a professional.