Comparing the cost of heating between different types of fuels such as propane, fuel oil, or even wood is a difficult task for consumers. One reason for the confusion is that each fuel is sold in a different unit of measure:
- Propane by the gallon
- Wood by the cord
- Electricity by the kilowatt-hour
- Kerosene by the gallon
- Coal by the pound
- Fuel oil by the gallon
- Natural gas by the cubic foot or by the therm (100,000 BTU)
So how do you convert each to a common unit that allows an “apples-to-apples” comparison of costs?
Begin the comparison by converting any type of heating source to its equivalent cost per million BTU. This may seem like a strange unit of measure at first, but once you learn how to make the simple calculations, its value as a comparison tool is easy to see. It allows any type of energy, including electricity, to be compared on its heat output vs. dollar cost.
Certainly the efficiency of the heating device must be taken into account in any comparison. But first, it’s important to understand how to determine the cost per million BTU calculation.
Each fuel contains a different amount of heat when burned, known as its “heat content.” Burning a gallon of fuel oil releases more BTUs of heat than burning a gallon of kerosene or a gallon of propane. Refer to the table below to see the difference.
Notice also our earlier point about the units in which fuels are sold (gallons, pounds, cu. feet and cords.) Using the heat content of each fuel, and converting to a common value of dollars per million BTU ($ per MM BTU) allows a clearer comparison between fuels.
|Fuel Type||Heating Value|
|#2 Fuel Oil||139,400 BTU/gal.|
|Natural Gas||1,000 BTU/cu. ft.|
|Biogas||600 BTU/cu. ft.|
|Wood Pellets (premium)||8,200 BTU/lb.|
|Coal (Bituminous)||13,000 BTU/lb.|
|Electricity (resistance)||3.412 BTU/kWh|
As a simple example, let’s compare the cost of using kerosene and propane, burned in unvented portable heaters to the cost of an electric heater. Unvented heaters deliver all their heat of combustion into the room. Venting combustion gasses is done by opening a window a ½ inch, which is always recommended. Therefore, with this heat loss, the efficiency of the kerosene and propane heaters will be considered 95% efficient.
In terms of $ per MM BTU, at a price of $3.00 per gallon, the kerosene heater delivered heat for the lowest cost of $13.72 per MM BTU. Propane priced at $1.76 per gallon delivered a million BTUs for $20.23. The portable electric heater (at 10¢ per kWh) delivered warmth for slightly more, at $27.84 per MM BTU.
Members may realize that beyond price, there are other considerations, such as fire safety with open flame devices, air quality with unvented heaters, and the need to manually refuel tanks, compared to electric heating which is automatic. Also, we have not considered heat pumps and their much higher efficiency. But this simplified portable heater example illustrates the concept of comparing heating fuels on their equivalent $ per MM BTU.