Selecting the fuel and heating system best suited for your needs depends on many factors. These include: the cost and availability of the fuel or energy source; the type of appliance used to convert that fuel to heat and how the heat is distributed in your house; the cost to purchase, install, and maintain the heating appliance; the heating appliance's and heat delivery system's efficiency; and the environmental impacts associated with the heating fuel.

One somewhat simple way to evaluate heating options is to compare the cost of the fuel. To do that, you have to know the energy content of the fuel and the efficiency by which it is converted to useful heat.

Fuels are measured in physical units, such as gallons of oil or propane, cubic feet of natural gas, or kilowatt?hours or electricity (kWh). They are also measured by heat content. In the United States, the most commonly used value for expressing the energy value or heat content of a fuel is the British thermal unit (Btu). One Btu is the amount of energy needed to raise the temperature of one pound of water one degree Fahrenheit (F), when water is at about 39 degrees F. One "therm" is 100,000 Btu. For a more detailed explanation of heating values, see the discussion at the end of this fact sheet.

Btu Content of Fuels

Since the actual heat content of different types of fuels varies, the approximate average values are often used. The table below provides a list of typical heating fuels and the Btu content in the units that they are typically sold in the United States. The figures below are general references for residential heating applications only. Commercial and industrial users should obtain more precise values from their fuel vendors.

These standards of measurement make comparisons of fuel types possible. For example:

• The heat content of one gallon of fuel oil roughly equals that of 41 kWh of electricity, 137 cubic feet of natural gas, 1.5 gallons of propane, 17.5 pounds of air-dried wood, 17 pounds of pellets, a gallon of kerosene, or 10 pounds of coal.
  
  
• One million Btu is the heat equivalent of approximately 7 gallons of No. 2 heating oil or kerosene, 293 kWh of electricity, 976 cubic feet of natural gas, 11 gallons of propane, 125 pounds of air-dried wood, 121 pounds of pellets, or 71 pounds of coal.
  
  
• The efficiency of the heating appliance is an important factor when determining the cost of a given amount of heat. In general, the efficiency is determined by measuring how well an appliance turns fuel into useful heat. (The condition of the heat distribution or delivery system also affects the overall system efficiency.) Many types of space heating appliances must meet minimum standards for efficiency developed by the U.S. Department of Energy. Table 2 provides average efficiencies for common heating appliances.

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