Gallonequivalent

Gallonequivalent is a unit of energy content used to compare fuels by expressing their energy in terms of the energy contained in one US gallon of gasoline. The concept is most commonly encountered as the gasoline gallon equivalent (GGE), which converts the energy of a fuel into an equivalent number of gallons of gasoline. This allows comparisons across fuels such as natural gas, ethanol, propane, hydrogen, and electricity in a common energy framework.

One gallon of gasoline contains roughly 120 to 125 megajoules of energy, about 33.3 to 34.7 kilowatt-hours. To obtain a gallonequivalent, the energy content of the fuel is divided by the energy content of one gallon of gasoline. The result expresses how many gallons of gasoline would deliver the same amount of energy as the given fuel.

For example, hydrogen has an energy content of about 141 to 142 megajoules per kilogram. Using 125 MJ per gallon of gasoline as a reference, 1 kilogram of hydrogen is approximately 1.1 to 1.2 gallonequivalents, depending on the precise energy values used. Such conversions are commonly employed in policy analyses, consumer information, and fuel-technology comparisons.

Limitations include the fact that gallonequivalents compare energy content but not vehicle efficiency or energy conversion losses. Different powertrains (internal combustion engines, electric motors, fuel cells) use energy with varying efficiency, so GGE/GGE-like measures should be interpreted alongside real-world performance data. They are primarily tools for budgeting, forecasting, and high-level comparisons rather than precise performance metrics.

See also: gasoline gallon equivalent, energy density, fuel economy, energy units.