from http://www.eia.doe.gov/neic/infosheets/apples.html
Btu Conversion Factors
| Energy Source | Physical Units and Btu (Weighted Averages, 2008) |
|---|---|
| Electricity | 1 kilowatthour = 3,412 Btu (but 7,000 to 10,000 Btu of primary to generate the electricity) |
| Natural Gas | 1 cubic foot = 1,028 Btu 1 cubic foot = 0.01 therms |
| Motor Gasoline | 1 gallon = 124,000 Btu |
| Diesel Fuel | 1 gallon = 139,000 Btu |
| Heating Oil | 1 gallon = 139,000 Btu |
| Propane | 1 gallon = 91,333 Btu |
| Wood | 1 cord = 20,000,000 Btu |
The Btu conversion factors above are good approximations. EIA also provides specific conversion factors for analysts to compare across:
1Weighted averages across different contexts of each fuel such as imports, exports, production, and consumption.
What Is a Btu?
A "British thermal unit" (Btu) is a 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°F at the temperature that water has its greatest density (approximately 39°F).
Why Do We Use Btu?
One practical way to compare different fuels is to convert physical units of measure (such as weight or volume) into a common unit of measurement based on the energy content of each fuel.The British thermal unit (Btu) is a widely used measure of energy content.
Using Btu for Comparing Home Heating Fuels
How can you compare home heating fuel prices? You must compare the cost per heating value (Btu) of each fuel. See How do I compare heating fuels? for a fuel conversion calculator.
Using Btu for Comparing Electricity Generation Fuels
Suppose you have been assigned the responsibility of purchasing fuel for a large electric utility company. You need to keep costs down for you and your electricity customers. Which fuel would you choose to generate electricity — coal, oil, or natural gas? In 2007, average prices of fuel delivered to electric power plants were:
- $35.48 per short ton of coal
- $43.50 per 42-gallon barrel of oil
- $7.31 per thousand cubic feet of natural gas
The prices of each fuel look quite different, but you can compare the prices of their energy content by first converting to Btu.
A short ton of coal contains about 21 million Btu, a barrel of oil contains about 6 million Btu, and a thousand cubic feet (Tcf) of natural gas contains about 1 million Btu. After dividing price by energy content, you can see which fuel is least expensive:
| Price | Btu (Energy Content) | $/Million Btu | |
| Coal | $35.48 per ton | 21 million per short ton | $1.69 |
| Oil | $43.50 per barrel | 6 million per barrel | $7.25 |
| Natural Gas | $7.31 per Tcf | 1 million per Tcf | $7.31 |
So coal is actually the least expensive fuel on a price-per-energy content basis.
Of course, 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 2008, the United States used over 99 quadrillion (written out, 1 quadrillion is a 1 followed by 15 zeros) Btu of energy.
One Btu is approximately equal to the energy released by burning one of these matches.
Source: Stock photography (copyrighted)
One quadrillion Btu is a very large amount of 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.
- One quadrillion Btu is equal to 172 million barrels of crude oil.