A cold front is in and I just sold my propane tank to a young couple.
My main heat source is now the sun.
I have been opening and closing curtains to take advantage of direct sun and that heat gain. Closing them to slow heat loss.
Last month I made an active solar heater that works like a solar oven.
In this case the glass “top” is a west window. Two “oven” sides are 1x4s attached to the sides of the window frame. The third side is the window sill whic allows about 1×32 for cold air uptake. The forth side is at the top and is open. It leaves 4×32″ for warm air to escape.
I attached foil bubble insulation to the sides and it stretches across the back.
On sunny afternoons it generates a warmed air current just over 100º. A south window would generate heat most of the day.
My back up heat became two oil filled radiators. My electric bill for first month operation was $35. Only $10 more than last year. Much better than the average propane bill of $125 last year.