m Ransley errs again:

Nick you are an idiot, there is to little sunshine in winter to give a
net gain, the days are to short, the suns angle to low at Chicago
latitudes. I replaced a 6ftx9ft single pane S facing window with Tri
pane and insulating curtains, That alone cut my utilities in winter 10
%. You also Assume its always sunny in chicago.

You are wrong on all counts. Try numbers :-)

Nick