Comparing Heating Fuels
Selecting the fuel and heating system best suited for your needs depends on many factors: the cost and availability of the fuel and heating appliance, the heating appliance's and heat delivery system's efficiency, the heat content of the fuel, maintenance costs, comfort, and combustion emissions. Fuels are measured in physical units, such as gallons of oil, tons of coal, and cubic feet of natural gas. They are also measured by heat content: Btu (British thermal units), Therms (about 100,000 Btu), or Calories. One Btu is the amount of energy needed to raise the temperature of one pound of water 1°F. One Btu equals 252 Calories. One calorie is the amount of energy needed to raise the temperature of one gram of water by 1°C. Electricity is commonly measured in kilowatt-hours (kilo means one thousand); one kilowatt-hour (kWh) equals to 3,413 Btu (860,076 calories).
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 the average heat content of different fuels. The figures below are general references for residential heating applications only. Commercial and industrial users should obtain more precise values from their fuel vendors.
Table 1: Average Heat Content of Fuels Fuel Type No. of Btu/Unit (Kilocalories/Unit) Kerosene (No. 1 Fuel Oil) 135,000/gallon (8,988/liter) No. 2 Fuel Oil 140,000/gallon (9,320/liter) Electricity 3,412/kWh (859/kWh) Natural Gas 1,028,000/thousand cubic feet (7,336/cubic meter) Propane 91,333/gallon (6,081/liter) Bituminous Coal 23,000,000/ton (6,400,000/tonne) Anthracite Coal 24,800,000/ton (5,670,000/tonne) Hardwood (20% moisture)* 24,000,000/cord (1,687,500/cubic meter) Pine (20% moisture)* 18,000,000/cord (1,265,625/cubic meter) Pellets (for pellet stoves; premium) 16,500,000/ton (4,584,200/tonne)* Note: The moisture content of wood can greatly affect its heating value.
These standards of measurement make comparisons of fuel types possible. For example:
- The heat content of 2,000 pounds (907.18 kilograms) of bituminous coal roughly equals that of 22,337 cubic feet (626 cubic meters) of natural gas.
- The heat content of 1,000 cubic feet (28 cubic meters) of natural gas equals about 90 pounds (41 kilograms) of bituminous coal.
- One million Btu (252,000 kilocalories) is the heat equivalent of approximately 80 pounds (36 kilograms) of anthracite coal, 250 pounds (113.4 kilograms) of air-dried hardwood, 11 gallons (41.6 liters) of propane, 293 kilowatt hours of electricity, or seven gallons (26.5 liters) of No. 2 heating oil.
The efficiency of the heating appliance is an important factor when determining the production 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 distribution or delivery system also affects the overall system efficiency.) Many heating appliances must meet U.S. Department of Energy standards; and manufacturers are required by Federal law to place energy efficiency labels on the appliances. Table 2 provides average efficiencies for common heating appliances.
Table 2: Estimated Average Fuel Combustion Efficiency of Common Heating Appliances Fuel Type - Heating Equipment Efficiency (%) Coal (bituminous) Central heating, hand-fired 45.0 Central heating, stoker-fired 60.0 Water heating, pot stove (50 gal.[227.3 liter]) 14.5 Oil High efficiency central heating 89.0 Typical central heating 78.0 Water heater (50 gal.[2227.3 liter]) 59.5 Gas High efficiency central heating 92.0 Typical central heating 82.0 Room heater, unvented 91.0 Room heater, vented 78.0 Water heater (50 gal.[227.3 liter]) 62.0 Electricity Central heating, resistance 97.0 Central heating, heat pump 200+ Ground source heat pump 300+ Water heaters (50 gal.[227.3 liter]) 97.0 Wood & Pellets Franklin stoves 30.0 - 40.0 Stoves with circulating fans 40.0 - 70.0 Catalytic stoves 65.0 - 75.0 Pellet stoves 85.0 - 95.0
Comparing Fuel Costs
You can use the following method to estimate the costs of producing one million Btu (252,000 kilocalories) of heat using different heating appliances and fuels. To do this, you need to know the efficiency of the appliance and the unit price of the fuel. Contact your utility or fuel supplier for the unit price of the fuel in question. Remember, the fuel price should not be the sole measure for selecting a heating appliance.
To use the formula below, remember to use a decimal for the appliance heating efficiency you are assuming (see Table 2). You must also first convert the Btu content of the fuel per unit to millions of Btu by dividing the fuel's Btu content per unit by 1,000,000. For example: 3,413 Btu/kWh (electricity) divided by 1,000,000 = 0.003413.
Energy cost ($ per million Btu)
Cost per unit of fuel Divided By
the Fuel Energy Content (in millions Btu per fuel unit) Times the Heating System Efficiency (decimal equivalent)
Note: the fuel costs used below are the national annual average residential fuel costs in 1999according to the Energy Information Administration (EIA). Prices will vary by location and season. Also, it is difficult to predict future costs for fuels. The system efficiencies used below are for these examples only.
- Electric resistance heat cost =
$0.082 (price per kWh) / [ 0.003413 x 0.97 (efficiency)] = $24.77 per million Btu.
- Natural gas (in central heating system) cost =
$6.60 (per thousand cubic feet) / [ 1.0 x 0.80 (efficiency)] = $8.25 per million Btu.
- Oil (in central heating system) cost =
$0.88 (price per gallon) / [ 0.14 x 0.80 (efficiency)] = $7.86 per million Btu.
- Propane (in central heating system) cost =.
$0.778 (price per gallon) / [ 0.0913 x 0.80 (efficiency)] = $10.65 per million Btu
This brief was reviewed for accuracy in February 2002.
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