A friend of mine is a plumber and he said you should consider the age of your home with respect to the size/material of the water lines. He also mentioned that with a large family (he has 3 kids)he didn't recommend the tankless systems. My neighbour did a full reno (demo down to the studs) and installed new water lines with a tankless system. He is quite happy with it however there are only two adults in the home.