What Is a Btu?

British thermal unit (Btu): The Btu is a precise measure of the heat content of fuels. It is the quantity of heat required to raise the temperature of 1 pound of liquid water by 1^o Fahrenheit at the temperature that water has its greatest density (approximately 39^o Fahrenheit).

Why Do We Use Btu?   

To make meaningful comparisons of different energy sources, you must convert physical units of measure (such as weight or volume) into a common unit of measurement based on the energy content of each fuel. One practical way to compare different fuels is to convert them into British thermal units (Btu).

Examples of Btu Conversion Factors

Btu conversion factors: Some Btu conversion factors for delivered energy are as follows:

Putting Btu In Perspective

How can you compare home heating fuel prices? You must compare the cost per heating value (Btu) of each fuel. EIA has a calculator that makes that comparison easier to compare the cost per heating value of home heating fuels. See the answer to that frequently-asked question and a link to a useful calculator at: How do I compare heating fuels?

Another example is for industrial use. Pretend that you have been assigned the responsibility of purchasing fuel for a large electric utility company. Which fuel would you choose to generate electricity—coal, oil, or natural gas? In 2006, average prices of fuel delivered to electric power plants were $34.09 per short ton of coal, $37.66 per 42-gallon barrel of oil, and $7.11 per thousand cubic feet of natural gas. Tons of coal, barrels of oil, cubic feet of natural gas -- how do you compare apples and oranges?

• In 2006, a ton of coal used to generate electricity cost about 9 percent less than a barrel of oil and about five times more than a thousand cubic feet of natural gas. When these fuels are converted into Btu a short ton of coal contained about 21 million Btu, a barrel of oil contained about 6 million Btu, and a thousand cubic feet of natural gas contained about 1 million Btu.  Therefore, on a Btu basis, coal would be a cheaper fuel to consume, accounting for three times as much energy as oil and 20 times as much energy as natural gas. (Of course in this example cost is not the only factor to consider  when selecting a fuel. Environmental restrictions and equipment costs are some of the other factors that should  be taken into account).

Btu Quick Facts
A single Btu is insignificant in terms of the energy use in a single household or in the Nation's energy consumption. In 2006, the United States used nearly 102 quadrillion (written out, 1 quadrillion is a 1 followed by 15 zeros) Btu of energy: 40 quadrillion Btu of petroleum, 24 quadrillion Btu of natural gas, 23 quadrillion Btu of coal, 8 quadrillion Btu of nuclear energy and 7 quadrillion Btu of renewable energy.

• One Btu is approximately equal to the energy released in the burning of a wood match.
• One million Btu equals about 8 gallons of motor gasoline.
• One billion Btu equals all the electricity that 300 households consume in one month.
• One trillion Btu is equal to 500 100-ton railroad cars of coal intended for electric power plants.
• One quadrillion Btu is equal to 172 million barrels of crude oil.