THE COST OF COMMON FUELS:

To compare costs of different fuels, we have to put them all on a common base.   In the US, where the old foot-pound system is still in use, that common base is "BTUs per dollar".  The British Thermal Unit (BTU) is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. If you light a paper match, it will put out about one BTU of heat energy before it burns your fingers.

No.2 Oil: One gallon of heating oil has a potential energy content of 140,000 BTUs. Today's oil-fired space heaters operate at about 80% efficiency.

If a gallon of home-heating oil costs $2.25, and is burned in a boiler or furnace at 80% efficiency, the homeowner will pay about $1.00 for every 50,000 BTUs of heat energy that actually go into the building.

140,000 times .8 divided by $2.25 =  50,000 BTUs per $.

Street Gas: The gas piped into your home is metered in "CCF", meaning "100 cubic feet".   There are about 102,000 BTUs in one CCF of street gas. However, you are probably billed in "Therms". One therm equals 100,000 BTUs. Although older central gas heaters may have efficiencies as low as 60%, today’s gas heaters range in efficiency from 90% to as high as 96%. From the product literature, or from your gas supplier, you can find out which efficiency figure applies to your unit.

If the bill says $2.15 per therm, and the hot-air furnace is rated at 91% efficiency, it costs  $1.00 for every 40,400 BTUs of heat energy going into the heating system.

100,000 X .91 divided by $2.15 =  40,400 BTUs per $.

Oil usually comes out ahead under that kind of comparison.   However, there are other considerations. To read about things like first-cost and adaptability, go to Space Heat.

Bottled Gas: As for Propane, bottled gas, there are about 92,000 BTUs in a gallon. If Propane costs $2.35 per gallon, with a boiler rated at 91% efficiency, that homeowner is only getting 35,600 BTUs for every $1.00 spent on fuel.

92,000 X .91 divided by $2.35  = 35,600  BTUs per $ .

Electric Heat: One kilowatt of electricity going through a resistance heater, puts out 3,713 BTUs of heat energy per hour.  It doesn’t matter whether that resistance is in a baseboard convector, or an electric stove, or one of the highly-advertised liquid-filled units, one KWH of electricity through that heating element will result in a heat output of the same 3,713 BTUs.

In this case, efficiency is rated at 100%, because there is no stack loss, no heat radiated into a basement, etc. If the utility is billing at $.15 per KWH, the building owner will pay $1.00 for a mere 24,700 BTUs of heat energy going into the space.

3713 x 1.00 divided by $.15  =  24,700 BTUs per $

Alternative Fuels: The Renewable Energy sources that we explore later, and to which we devote most of our attention in the upcoming periodical, don’t have to deal with “BTUs per $”. Instead, resources like sunlight and wind and tide will be evaluated, in these pages at least, on the basis of Return on Investment.