The size of you still will ultimatly decide the size of element needed, the larger the still, the more power it will require to run it efficiently. Your element sizes are generally set at 2400W and 3600W. Each 3600W element will require its own dedicated circut with a 15A power point. 2400W elements can be run off a normal power circut but each element should be supplied by a separate circut .
I would think at a minimum you would want 3 x 2400W elements, that would bring 120L of wash to boiling in a bit over an 1hr. I used the calculator on
This Page. I set the start temp at 25C, end temp at 90C and boiler efficency at 75 for uninsulated and 90 for an insulated boiler.