[Griff]

It is difficult to quantify. Nothing too dramatic in terms of the whole house since the passive solar face already does a lot for us on sunny days but it does take the edge off the basement room it is plumbed to. On a bright sunny day it will lift that small insulated room maybe 20 degrees F. When the ceiling and finish work is done it'll be interesting to see how it holds heat. I guess an insulated house with poor solar gain or tightly insulated workshop in an unheated building would be good applications. Since it draws from the floor it is heating the coldest air in the space, so that is pretty helpful. I wouldn't over sell it but it is a great feeling when you hear the blower come on knowing the sun is the only input post manufacture.