I have a 25 yr old split entry home. It is 2400 sq ft, 1200 over 1200. There is 2000sq ft living space, 400sq ft workshop and boiler room with R-19 walls, R-38 ceiling, a well ventilated attic, but the Anderson windows are getting a little old.
Calculated heat loss: 60KBTU/hour, living space; 25KBTU/hour, workshop and boiler room (It has 2 uninsulated garage doors with vents!).
I heated the home to 72degF and the boiler coil supplied DHW for 9 months for a family of 4 (2 adults and 2 teenage girls). The balance of the year (June-July-August) the house is unheated and electricity is used to heat the DHW.
I used about 5 tons of coal each year for the last 7 years in my Axeman Anderson Anthratube 130-M. This year, even though it's been colder, I am still on track to burn the same 5 tons, maybe a half ton more than normal. I have been using buckwheat which I think has been more efficient in my situation. I have a bin that can hold ten tons easily and I keep it full with an annual July or early August purchase, who knows what can happen. Coal is cheap, stable, and safe in storage. In this age when fuel prices are rising and the banks pay nothing in interest for savings accounts, extra coal in the bin is like money in the bank!