I have a 20x40 IG - & installed 6 panels (4 x 20) on my roof (south facing) in west PA last year. I can get 8 degrees a day - best case I got 30 degrees in 3 days last year on opening - but easily kept it 86 or higher all year using solar cover at night.

This was well worth the effort - this year I'm selling the heat pump.

If you are interest in solar panel you must read the page tphaggerty recommended - powermat.com. It is the best source to educate yourself on how they work. His recommendation helped me out alot last year.

There was no local installers in my area - I purchased the panels online (not from powermat) and found a local Gen Contractor to attach to the roof.