What is a GGE?
A gasoline gallon equivalent (GGE) is the volume of natural gas it takes to equal the energy content of one liquid gallon of gasoline. Since natural gas is not a liquid, its volume is measured in cubic feet (CF), rather than gallons. Therefore, the GGE is a way of comparing equivalent volumes of fuel based on their energy content in British Thermal Units (Btu). The GGE of CNG is 123 CF and this volume of CNG has the same energy content as one gallon of gasoline (based on 929 BTU/CF of CNG and 114,264 Btu/gallon of gasoline). Since the other alternative fuels are liquids at room temperature, their Btu is based on the energy in one liquid gallon and there is no need for a conversion or GGE.
