How much money did I save using my woodstove this year?

We burn about a cord of firewood in our Jotul F-100 Wood stove every year.   Our primary source of heat is the oil fired boiler in the basement,  the wood stove is a supplemental or backup source.  On those really cold nights, of which we have had a few this winter, it is nice to sit around the warm fire.

I thought it would be interesting to see how much money we saved every year with the wood stove.  There are several factors involved in this, namely, the heat value of the wood we are burning, the efficiency of the wood stove, the heat value of the oil we are burning,  the efficiency of the boiler and the cost for the fuel.

fire wood

According to Woodheating.org, (linked to by the DOE wood heating web site), black cherry contains 23,500,000 BTU/cord (assumes >20% moisture).  A cord measures 4 x 4 x 8 feet.  Of course, these numbers are approximations, but for my purposes, they will work.

My wood stove is 74% efficient, according the the manufacture’s data sheet.  Therefore, I get 23,500,000 BTU  x .74  = 17,390,000 BTU heat per cord of cherry firewood.

My Furnace is 84.5% efficient, according to the last time it was serviced.  A gallon of heating oil contains 139,000 BTU.  Therefore, I get 139,000 BTU x .845 = 117,455 BTU heat per gallon of oil.

If I burned a whole cord of wood this year, I generated 17,390,000  BTUs of heat for my house.  I therefore avoided using 17,390,000 BTU ÷ 117,455 BTU/Gallon oil = 148 Gallons oil.

I get my fire wood for free.  Heating oil costs about $2.76/gallon, so I saved 148 gallons x $2.76/per gallon = $408.63 which is a little too precise.  I’d say $408 ±5% to account for imprecise qualities of cord wood and wood moisture content.

We are almost out of fire wood for this year, on account of it being cold.  Next year when the solar heaters are attached to the side of the house, it will be interesting to see how much oil is saved.