Stockingfull, your house must have been built for electric heat. At one house I helped build, the electric company came by to give us a quote and estimate of yearly bills for electric heat.
The amount of insulation that electric heat required and better windows told the tale. With the same insulation and windows [expensive] natural gas still won the pricing war.
So if your house was designed for electric heat it is a tight, well insulated house with good windows. That is why you have such low coal usage. It is amazing to heat that much house for that little.
My ~4000 sqft farmhouse is the opposite, drafty and poorly insulated, I have improved the insulation and windows where I could. but my place still would cost $6-7000 per winter season to heat to 62* burning propane.
With coal, I burn 2-3tons per cold month, so lets say $600/month, the house is at 68-70*, and I have unlimited hot water too. So my coal bill for the year will be about $1800, not bad at all.
My propane company isn't happy=I'm happy