Well Its a month later than the post but I do use solar as a helper. I have one homemade passive collector it's' 2X8' It dosent work every day but a lot of times this winter it was 6 -10 degrees and the sun was out the collector was running an internal temp of 157 to 160 Degrees.
I use a small 30 cfm fan (like Computers use) that is turned on by a differental thermostat at 90 degrees
Those days as long as the sun was out my gas furnace was quiet that saves some on the energy bill
Here is the link to the place I got the blueprints the collector will cost 100 to 150. dollars to build I feel I got that back last winter. I'm adding another this year.
Mobile Home Repair- Building an inexpensive solar heating panel