I heated my home office building and Amateur Radio operating building with an alternate fuel source during the Winter of 2001. It was instructional to compare different fuel sources, and record fuel usage data on how I was actually using BTUs. This page is a quick reading page of the results with actual numerical comparison. Please credit this web page as the source for any information you relay to others, or link directly to it if you're building a web page.From the end of September 2000 to mid-April 2001, I heated my 640 ft2 of office space for about 12 hours on each of 55 days (26% of the days). I used 2400 lb wood, which occupied approximately 170 cubic feet (about 1.3 cord). The Oregon Department of Agriculture puts out a wood fact sheet saying the energy equivalent is about 7000 BTU per pound of wood similar to type and condition of what I burn. The "seasoned" wood tables show about 2500 lb weight per cord. I'm showing about 1800 lb per cord, which checks because mine wasn't all hardwood, and within the precision I measured weight and volume of the wood used.
So, I'm burning about 305,000 BTU of wood per heating day,
60% efficiency in my stove, delivering about 183,000 BTU.
electricity is 100% efficient, this corresponds to 54 KWH per day (3413
BTU/hr per KW). Using my local winter post-tax rate of 7.8 cents per
that's about $4.19 per day I'm not spending on heating my office. Total
savings this winter of $230 compared to electricity - more if
heated more days or longer hours.
My numbers say my wood office stove gives 14,000 BTU/hr. In order to give this numer some meaning, it can be compared to other common heat sources. My small propane heater gives 8,000-14,000 BTU/hr, and my portable electric heaters are 1000-1500 Watt (or 3400-5000 BTU/hr). Corn burners are available in the 30,000 to 200,000 BTU/hr range. My propane barbecue grill is about 40,000BTU/hr.
Comparison Summary of my options:
Corn @ $2.05/bushel, 80% efficient, gives 200,000 BTU per dollar.I've seen others use a wag of 100 million BTU per year to heat an average older farm house. Tracking my home propane use rate through the calendar year of 2000 came up with 107 million BTU. I'm a pretty agressive about turning down the thermostat, so actual usage for others may be higher, but the wag is not far off. To compare annual costs, the cost for 100 million BTU are shown below. If you use more, savings will be more. Although not currently an option for me, I included natural gas data from the Department of Energy in the table below for others to use as a comparison:
Electricity @ $0.08/kWh, 100% efficient, gives 42,700 BTU per dollar.
Propane (bulk) @1.25/gal, 92% efficient, gives 66,600 BTU per dollar.
Propane @$11.60/20lb, 92% efficient, gives 34,100 BTU per dollar.
Wood @$125/cord (local costs), 60% efficient, gives 60,480 BTU per dollar.
|Shelled, dry corn @ $2.05/bushel||
|Natural Gas @ $0.93/therm||
|Propane, bulk @ $1.25/gal||
|Wood, @ $125/cord||
|Electricity, @ $0.08/KWH||
|Propane, 20lb tanks @$11.60/ea||
Propane has to go up to $1.41/gal before wood is cheaper.
Propane has to go up to $2.00/gal before elec is cheaper.
Propane has to go down to $0.44/gal to beat corn.
Using a local electric heater is cheaper than a local propane heater.
Mitigating this somewhat (making the payback period longer) is the consideration that I could have have used the $2100 as additional mortgage payment, saving me 7.5% a year. That's about $330 over 2 years, so add another 4 months on the payback period.
A corn burning stove has an auger motor, a combustion motor, and a convection motor. For the unit I'm looking at, it's a steady 285 Watts while running full bore. My propane house furnace uses about 440 Watts, but according to recorded Home Heating Data Graphs, it only comes on for 16% of the time during a 38 degree day, or an average of 70 Watts.
The corn burner heat output is adjusted by slowing down the blower and auger, as compared to the furnaces digital on/off behavior. Absolute worst case would be if you kept the corn burner on full bore 24 hours per day. In this case, over the course of a 30-day month, the corn burner would use 155 KWH more, or $12 in my case.
Sounds bad, eh? Actually, if you add up the electricity and fuel costs for each hour of operation, you get $1.12 for propane, and $0.22 for corn. The propane furnace kicks out 74,000 BTU and the corn stove kicks out 40,000 BTU. Making this correction to fairly compare them, leaves propane costing me $0.60/hr and corn costing me $0.22/hr. This shows corn is 36% of the cost instead of 30% from the table above. And remember, temperatures colder than 38 degrees make the numbers shift to favor the corn (furnace duty cycle increases and uses more electricity per hour).
Even if you intend to move sooner, consider that many corn burning stoves are zero-clearance UL Approved devices. In other words, you can stand them on your carpet floor, right next to the wall, with bookshelves on both sides. The only modification to your house is a single 5 or 6" hole through an outside wall ..not much more than a dryer vent. Think of this as a wash machine. Even if you sell your house, you can take it with you.