Energy Calculator  Common Units and Conversions
Calculators for Energy Used in the United States: Petroleum (42 gallons in a barrel)  

Scientific notation is a shorthand way of writing a number that has a lot of digits. For example, the number 525,000,000 could be written as 5.25E+08. The "+08" tells you to move the decimal eight places to the right. A negative number after the "E" would tell you to move the decimal a certain number of places to the left. For instance, 5.25E03 is the same as 0.00525.
Physical units reflect measures of distances, areas, volumes, heights, weights,
mass, force, impulse and energy. Different types of energy are measured by different
physical units: barrels or gallons for petroleum; cubic feet for natural gas;
tons for coal; kilowatthours for electricity. To compare different fuels, we
need to convert the measurements to the same units.
Some popular units for comparing energy include: British Thermal Units (Btu), barrels of oil equivalents, metric tons of oil equivalents, metric tons of coal equivalents, and terajoules.
In the United States, the British Thermal
Unit (Btu), a measure of heat energy, is the
most commonly used unit for comparing fuels. Because energy used in different countries comes from different places, the Btu content of fuels varies slightly from country to country. The Btu content provided below and used in the energy calculator reflect the average energy contents for fuels consumed in the United States.
BTU Content of Common Energy Units
1 barrel(42 gallons) of crude oil = 5,800,000 Btu
1 gallon of gasoline = 124,000 Btu (based on U.S. consumption, 2007)
1 gallon of diesel fuel = 139,000 Btu
1 gallon of heating oil = 139,000 Btu
1 barrel of residual fuel oil = 6,287,000 Btu
1 cubic foot of natural gas = 1,028 Btu (based on U.S. consumption, 2007)
1 gallon of propane = 91,000 Btu
1 short ton of coal = 20,169,000 Btu (based on U.S. consumption, 2007)
1 kilowatthour of electricity = 3,412 Btu
Some simple examples of converting physical units to Btu, in order to compare energy content and costs, are provided below.
Example 1:
You have a natural gas furnace in your home that used 81,300 cubic feet of
natural gas for heating last winter. Your neighbor has an oil furnace that used
584 gallons of heating oil last winter. To determine which home used more energy
for heating, you can convert the natural gas and heating oil consumption figures
into Btu, as follows:
Natural Gas: 81,300 cubic feet (your house) 
x  1,028 Btu cubic foot 
= 83,576,400 Btu 
Heating Oil: 584 gallons (neighbor's house) 
x  139,000 Btu gallon  = 81,176,000 Btu 
Answer: You used more energy to heat your house!
Example 2:
You work for an electric power company. Your company’s power generators can run on one of two fuels: natural gas or residual fuel oil. Your job is to switch fuels when the cost of the fuel you are currently using becomes more expensive than the other fuel. This will keep costs down for you and your electricity customers. Your company’s generators are currently using residual fuel oil but fuel oil prices have been going up much faster than natural gas prices. Based on the fuel costs below, you need to decide if it is time to switch to natural gas:
Natural Gas: 
$7.30 thousand cubic feet 
x  1,000 cubic feet 1.028 million Btu 
=  $7.10 million Btu 
Residual fuel oil: 
$57.75 Barrel 
x  1 barrel 6.287 million Btu = 
$9.19 million Btu 
Answer: When you convert the fuels into the same units, you see that residual fuel oil now
costs more than natural gas. You decide to switch to natural gas
to save money.
Last Revised: December 2008
Sources: Energy Information Administration, Annual Energy Review 2007, June 2008.
Barrels/gallons to metric ton conversions: Energy Information Administration, International Energy Annual 2008, June 2008.
Energy Information Administration, Natural Gas Navigator data, August 2008.
Energy Information Administration, Petroleum Navigator data, August 2008.
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