Wood and Coal Stove Advisory

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The True Economics of Wood Heat

In Wood Heat's infancy, we ingenuously equated the heating value of one cord of wood to a 200 gallon tank of #2 fuel oil or a ton of coal. With stove coal costing about $80/ton and oil going from a 25¢ to $l/gal and still rising, we figured we were heating dollars ahead if a cord cost less than $100. A $50 cord of wood looked a bargain compared with any commercial fuel.

But after Jay Shelton and other wood-fuel researchers put their calculators to work, we learned that wood-heat economics was complicated and had to be worked out in BTUs (British Thermal Units).

One BTU is the energy needed to heat one pound of water one degree Fahrenheit. A gallon of #2 oil contains 139,000 BTUs of which 15 percent are lost in a modern, 85 percent efficient oil-burner for 120,000 useable BTUs; 200 gallons provides about 24 million BTUs. A ton of good-quality coal burned in a typical 60 percent-efficient stove gives off some 14 million BTUs. An air-dried cord of hardwood contains about 25 million BTUs, which, if burned in a top-flight, 80 percent-efficient wood-stove, delivers 20M BTUs—the heating equivalent of 167 gallons of fuel oil or a ton and a half of coal. At an oil price of 90¢/gal, you'd break even if you paid as much as $150 per cord of wood. Older, pre-EPA stoves are lucky to manage 55 percent efficiency. Their break-even remains about $100/cord; a traditional woodburner paying more is losing money.

But, fuel cost is just one part of the total—the portion that stove suppliers prefer to quote in claiming savings. The purchase, installation, and maintenance costs of a stove/pipe/flue combination amortized over its lifetime effect the true total cost of wood heat. Push some numbers before you accept any stove-merchandiser's claims of cost savings.

An EPA-approved stove large enough for serious house heat will set you back from $350 to $2,000. The building code code prohibits exhausting fossil-fuel and wood stove heaters into the same flue, and a wood-only, fire-safe ceramic-lined ceramic chimney or insulated stainless steel flue will cost $500 to several times that. Stovepipe, stoveboards, and heat-shielding can add another several hundred dollars. Expect to invest perhaps $3,000. Prorate the cost over eight years (the average time a typical American family spends in one house), then add in the annual cost of fuel and plant upkeep.

Here is a cost analysis for an average home in the northern tier, with fossil-fuel backup used in coldest weather or, in inversion-ceiling areas, on no-burn days when air is too polluted for wood fires:

This is about the same amount that most homeowners pay for a year's supply of fuel oil. Coal in a central furnace or a pair of stoves would cost about the same. It's a wash. And, remember, the fossil-fuel backup system is constantly depreciating, wood stove or no.

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