Actually not true. It is easier if 1 of them is the companion then all you need are simple patch cords. However there are several kits available that allow you to hook up 2 or even 3 of the eu2000i together. I boought 2 of the eu2000i many years ago before the companion model was available and i have a parallel kit that works great. Great little units, build yourself and extended run tank and you can run all week and never fill up.