I'm heating my 1800 sq ft home with 4 s7's and it's wonderful. I live in central Canada and it's been a warm winter thus far but I have not had to use my other heat sources yet this year even when temps go down to -29 with windchill. Very simple to get the heat into house.. i run s7's in vertical position and have a 16' flexible tube that moves the heat to upper level where i can store it or use it by simply turning on a fan on.
  The noise of the psu's is a work in progress but have got it down where it is "wife approved" lol

These 4 s7's not only pay for power bill and I get 100% heat recovery.. they pay for my mortgage and bills as well