Comparing Fuel Costs

One would think comparing the costs of different heating fuels and electric heat sources would be pretty easy. That’s not the case. For starters, while we purchase some fuels by the energy content of the fuel, we purchase others by volume or weight—and we use different units for different fuels. Heating oil, propane, and kerosene are sold by the gallon, natural gas by the hundred cubic feet (ccf) or therm (100,000 Btus), firewood by the cord, wood pellets and coal by the ton, and electricity by the kilowatt-hour (kWh).

To further complicate matters, the amount of usable heat we get from a fuel also depends both on the efficiency of a given heating device and on how efficiently that heat is distributed to the conditioned space. The efficiency of combustion appliances varies widely, from a low of about 40% for older woodstoves to over 95% for condensing gas furnaces. Electric-resistance baseboard heaters are 100% efficient, while heat pumps, which use electricity to move heat from one place to another instead of converting the electricity directly into heat, range in efficiency from 200% to over 300%. (These numbers don’t account for the “upstream” energy costs of fuel production, nor do they begin to account for environmental costs—which are pretty significant with some forms of electricity generation.)


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