- Btu: British thermal units, or the unit of measure to show an amount of energy.
- Heating value: A measure of energy content in Btus, which represents the amount of heat released during combustion. Typically, we use the lower heating value when comparing fuels.
- Gasoline gallon equivalent (GGE): The amount of fuel that has the equivalent energy to a gallon of gasoline. Similarly, diesel gallon equivalent (DGE) is the amount of fuel that has the equivalent energy to a gallon of diesel. GGE is used for alternative fuels that typically replace gasoline (e.g., ethanol), whereas DGE is used to measure fuels that replace diesel (e.g., liquefied natural gas, or LNG).
- Alternative Fuels Data Center’s Laws and Incentives website (http://www.afdc.energy.gov/
- National Renewable Energy Laboratory’s A Primer on Motor Fuel Excise Taxes and the Role of Alternative Fuels and Energy Efficient Vehicles (http://www.nrel.gov/docs/