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A gasoline gallon equivalent, or GGE, is the amount of an alternative fuel that holds the same energy as one gallon of gasoline. It lets a buyer compare prices across fuels on a fair, common measure.
Many alternative fuels are not sold by the gallon at all. Natural gas sold as vehicle fuel is measured by weight, and hydrogen is sold by the kilogram. That makes a head-to-head price hard to read, because a gallon of one and a kilogram of another are not the same amount of usable energy.
The gasoline gallon equivalent solves it by anchoring everything to a familiar unit. You figure out how much of a given fuel carries the same energy as one gallon of gasoline, and you compare it per GGE. Now a driver can stand at the pump and compare a dollar figure that means the same thing across every fuel.
For a fuel seller, the GGE is a common way to post a price on compressed natural gas. It keeps the comparison square with the gasoline a customer already understands, so no one is fooled by a low number that buys less energy than it looks like it should. State weights and measures rules set the unit each fuel is sold in, and the national model rules call for the kilogram for hydrogen.
In useThe station prices its compressed natural gas per gasoline gallon equivalent, so a driver can compare it straight against the gasoline price on the next island.
See also Energy economy ratio (EER), British thermal unit (BTU), Electric vehicle (EV)