Heating with Wood

Comparing Fuel Costs

In the winter of 2007/2008 the costs of home heating rose dramatically in the U.S., particularly for those homeowners who used fuel oil or propane for heating.  According to the Energy Information Administration (part of the U.S. Dept. of Energy) the average cost of residential home heating oil in the U.S. in February of 2008 was $3.40 per gallon.  This represents a 94% increase in price from just one year before. Homeowners who used propane did not fare a lot better.  The cost of propane was $2.55 per gallon which represents a 52% increase in the cost of propane in one year.
Given these dramatic rises in the cost of home heating many homeowners are considering switching to wood as a way of heating their homes.  The key question is does this make economic sense?  In order to answer that question there are a number of factors to consider:

1. How efficient is your stove or fireplace?  Probably the most critical factor is the efficiency of your wood stove or wood furnace.  If you just have a standard open fireplace it is almost certainly not efficient enough to use economically for home heating.  On the other hand most modern wood stoves are between 60% - 80% efficient.  One option you might want to consider if you have a standard fireplace is a fireplace insert.  Inserts are relatively easy to add to an existing fireplace and are nearly as efficient as wood stoves.
2. Do you have the ability to harvest wood locally?  In rural parts of the country there are often free sources of wood either on your own property or in publicly accessible national forests.  If your wood is free then the economics are always better.  However, be honest with yourself.  Consider the time it is going to take you to harvest the wood, cut it and stack it.  In some cases you will be better off buying it given the labor costs even when it is free.
3. What is the cost of a cord of wood or other bio fuels in your area? such as sawdust pellets or corn kernels?  The average cost of firewood in the U.S. in 2008 is about $190 a cord.  However, prices varied considerably by region.  There is also a lot of misleading terminology when it comes to buying firewood.  Make sure the vendor is using a standard cord which is 4x4x8 feet and includes a significant amount of hard wood, not just lightweight pulp wood.  If you are using a pellet stove then you need to see what the price of the pellet fuel is for your area, though this tends not to vary as much as the price of firewood.
4. How much space do you have to heat and how much of it would be heated by a wood stove? Generally, the larger your home the better the economics of heating with wood start to be.  However, in many homes the floor plan is such that there a single stove cannot heat all of the rooms.  In these situations you need to look at using a woodstove with a fan to get better heat distribution or possibly consider a wood furnace which can be hooked up to your forced air heating system. 

Comparing Wood with Other Fuel Sources
In order to compare the cost efficiencies of different kinds of heating approaches you need to translate the fuel metrics into a common measurement of heat.  The best metric to use is the BTU (British Thermal Unit).  Then what you need to understand is the equivalents between the different fuels in terms of the number of BTU's in a cord of fire wood  We have already done this analysis for you in the table below:

Type of Fuel	Compare Energy in BTU's for 1 Cord of Wood
#2 Fuel Oil (in gallons)	Divide by 175
Coal (in pounds)	Divide by 1600
Natural Gas (thousands of cubic ft.)	Divide by 28
Propane Gas (in gallons)	Divide by 220
Electricity (in kilowatts)	Divide by 6,500

Lets work through an example.  Assume that you used 1000 gallons of fuel oil this winter. To determine how many cords of wood you would need to get the same amount of heat simply divide the 1000 gallons by 175 as per the chart and you will see that it would take the equivalent of 5.7 cords of wood to provide the same heat energy.  Now you can make an initial comparison.  At $3.40 per gallon a 1000 gallons of fuel oil would cost you $3,400.  On the other hand at $190 per cord the 5.7 cords of wood would cost you $950.  That's a pretty dramatic difference!  Unfortunately it is not quite that easy.
In order to get an accurate comparison you have to account for the fact that wood stoves vary greatly in their efficiency as compared to an oil furnace. In order to make your comparison more accurate first divide the estimate of the number of cords (5.7 cords in this example) by the efficiency rating of your wood stove.  In this example, if the wood stove is 70% efficient then 5.7 divided by 0.70 = 8.14 cords.  In other words it is actually going to take 8.14 cords of wood to provide the heat you need given that the wood stove is not completely efficient.  Now you can re-run your estimate.  8.14 cords of wood at $190 per cord equals a total wood cost of $1,546 as compared to $3,400 for fuel oil.  This means that at current prices heating with wood is less than half the cost of heating with fuel oil! Quite a difference!
You can use this approach with any of the fuels listed in the above table and quickly calculate how cost efficient wood would be as a heating source compared to what you are using now.  To be completely accurate you should include the cost of a new wood stove if you don't have one. However, that cost should be very low when annualized given that most good wood stoves can last a lifetime.  Also, keep in mind that the above example was calculated on prices as of February 2008.  It is highly likely that fuel oil costs will probably continue to rise significantly in the future.  It is also probable that wood prices will go up with demand, though it is unlikely that they will go up as dramatically as oil and natural gas since wood is a renewable resource.