Sidebar: Comparing Costs

You also may compare LP gas cost to diesel fuel cost based on these BTU/gallon numbers.

  • LP gas contains roughly 90,000 BTUs per gallon.
  • Diesel fuel is approximately 140,000 BTU per gallon.
  • For every million BTU of heat, you will need 11.11 gallons of LP gas.

For the same amount of heat, you will need 7.14 gal of diesel. Therefore, one gal of LP gas equals 0.64 gal of diesel in heat content.

Remember, when purchasing diesel fuel for a boiler or heater, the highway taxes do not apply. To see how this works out mathematically, here is an example: At $2.50 per gallon, one million BTU of diesel fuel will cost $17.85. In order to provide the same amount of heat at the same cost, the cost of the LP gas will be $1.60 per gallon.

To compare the cost of electric power to provide the heat, let us use $0.10 per kilowatt-hour for the average cost of electricity. (It is more in some areas and less in others. Check your local supplier for accurate electric, natural gas and LP gas cost.)

For ease of calculations, I will use some rounded off numbers for the ratio of one kilowatt-hour (kWh) equals 3,350 BTU/hr, or 10 kW equals 33,500 BTU/hr, or one boiler horsepower. Therefore, for the amount of electrical energy needed to produce one boiler horsepower in a boiler or thermal oil heater will cost $1.00. The cost of one million BTU will then be $29.85 for 298.5 kilowatt-hours of electric power.

Natural gas contains an average of 1,000 BTU per cubic foot. Gas companies typically bill customers by the therm, which is 100 ft3 of gas. Larger users will be billed by the dekatherm or 1,000 ft3 ft of gas, which equals one million BTU. For comparison, I will use $0.60 per therm for the average cost of natural gas (from a pipeline) in the year 2015.

Given that, for 1,000 ft3 of natural gas, or one million BTU of heat, that amounts to $6 per million BTU. Compared to $17.85 for diesel and $29.85 for electric, it is clear that natural gas is the best choice in this example. As noted, natural gas is often the fuel of choice when available due to cost.