For many rural homestead-dwellers, keeping warm in the winter can pose a bit of a problem. Living away from the hubbub of the city means you are closer to nature, but likely too far away from natural gas pipelines to be able to heat with natural gas. Thus, the heat fuel options are either having heating oil delivered to a tank, or heating with wood in a wood stove or wood furnace. Wood fuel is often said to be cheaper than oil, on top of its other benefits. But is heating with wood cheaper than oil?
To make the comparison for yourself, calculate the number of BTUs (British Thermal Units) you get per dollar with each fuel. Then, you can compare the cost of each for a season’s worth of heat. Here’s how to make the calculation:
- Look at the type of wood you burn (hopefully a nice hardwood) and the number of BTUs that a cord of it produces: Say it’s 11.5 million BTUs per cord (a conservative estimate).
- Find the efficiency rating of your wood furnace or wood stove — most are between 60% and 75%: Say it’s 70%.
- Calculate how many BTUs you get per cord: 11.5 million X 0.70 = 8.05 million BTUs per cord.
- Find the cost of that cord of wood (including delivery) and the number of BTUs you get per dollar: Say it’s $200 per cord. 8.05 million divided by 200 = 40,250 BTUs per dollar.
- Now compare that to your gas or oil costs: Say the cost is $4.00 per gallon. There are approximately 138,000 BTUs in a gallon of heating oil.
- Gas furnaces are given an AFUE (annual fuel utilization efficiency) rating to measure their efficiency. The lowest allowable is 78% and the highest available is 97%, so yours should be in that range: Say it’s 80%.
- Find how many BTUs you get per gallon of oil: 138,000 X 0.80 = 110,400 BTUs per gallon.
- Find the number of BTUs you get per dollar: 110,400 divided by 4.00 = 27,600 BTUs per dollar.
- Consider how much heat you usually need each winter, depending on your house size and just how toasty you like to keep it: Say you usually burn 5 cords of wood per winter, which produce about 40.25 million BTUs (with your 70% efficiency stove) and cost $1,000 altogether.
- Calculate what your cost would be for the same number of BTUs using the other fuel: 40.25 million BTUs divided by 27,600 BTUs per dollar = $1,458.33
In this example, heating with wood produced 31% more BTUs per dollar over heating with oil, making it 31% cheaper for producing the same amount of heat. That means a huge savings over oil over the course of a whole winter. You can also do the calculation to compare wood heat to natural gas.