I have 5000 Sq Ft Home and they work at 75 feet away, but i have one huge breaker box in the 3 car garage. - - - Each Powerline unit has a light to indicate if one box will work with the other box you have at the other end of your house - - - Green is what you want, if its amber color you don't want it at that electrical outlet because you will get slower speeds and its not worth using it there.