Gasoline Gallon Equivalent (GGE)

A gasoline gallon equivalent is the quantity of any fuel that holds the energy of one gallon of gasoline, about 112,000 to 116,000 Btu. A diesel gallon equivalent does the same job against diesel, at 128,488 Btu. For compressed natural gas, 5.66 pounds or 123.57 cubic feet is one GGE and 6.37 pounds is one DGE. A gallon of propane carries about 73% of a GGE. Electricity is compared by energy in the same way, which is why a kilowatt-hour can be priced against a gallon.

The unit exists because price per gallon lies across fuels. Propane quoted below gasoline per gallon is not cheaper if it takes more of it to go the same distance, and a fleet that compares a fuel contract or an alternative-fuel pilot on the pump price is comparing containers of different sizes. CNG is sold by the GGE at many stations for exactly this reason.

In a public fleet the GGE is what lets an alternative-fuel case survive a finance review. A cheaper-per-gallon fuel that burns faster reads as a saving on the fuel line and a loss on cost per mile, and the second number is the one a replacement or conversion decision rests on. The same trap sits under E85, which is priced below gasoline and carries less energy.

The practical habits are small. Ask a vendor to quote per GGE or DGE alongside per gallon, and track consumption in energy units across a mixed fleet so cost per mile is comparable between a CNG refuse truck and a diesel one. Emissions reporting uses the same energy basis, so a fleet that already keeps it has half of that work done.