Gasoline Gallon Equivalents (GGE)

Fuel Energy Comparisons

Energy tank drawing on a blackboard
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In the simplest terms, Gasoline Gallon Equivalents are used to determine the amount of energy produced by alternative fuels as they compare to the energy produced by one gallon of gasoline (114,100 BTUs). Using fuel energy equivalents provides the user with a comparison tool for gauging various fuels against a known constant that has relative meaning.

The most common method for gauging fuel energy comparisons of measurement is the Gasoline Gallon Equivalents, illustrated in the chart below which compares the BTU generated per unit of alternative fuel to the output of gasoline, measuring it out in a gallon equivalent.

Gasoline Gallon Equivalents
Fuel TypeUnit of MeasureBTUs/UnitGallon Equivalent
Gasoline (regular)gallon114,1001.00 gallon
Diesel #2gallon129,5000.88 gallons
Biodiesel (B100)gallon118,3000.96 gallons
Biodiesel (B20)gallon127,2500.90 gallons
Compressed Natural Gas (CNG)cubic foot900126.67 cu. ft.
Liquid Natural Gas (LNG)gallon75,0001.52 gallons
Propane (LPG)gallon84,3001.35 gallons
Ethanol (E100)gallon76,1001.50 gallons
Ethanol (E85)gallon81,8001.39 gallons
Methanol (M100)gallon56,8002.01 gallons
Methanol (M85)gallon65,4001.74 gallons
Electricitykilowatt hour (Kwh)3,40033.56 Kwhs
 

What’s a BTU?

As a basis for determining the energy content of a fuel, it is helpful to understand exactly what a BTU (British Thermal Unit) is. Scientifically, the British Thermal Unit is a quantifier of the amount of heat (energy) required to raise the temperature of 1 pound of water by 1 degree Fahrenheit. It basically boils down to being a standard for measurement of power.

Just as PSI (pounds per square inch) is a standard for measuring pressure, so too is a BTU a standard for measuring energy content. Once you have the BTU as a standard, it becomes much easier to compare the effects different components have on energy production. As illustrated in the chart about, you can even compare the output of electricity and compressed gas to liquid gasoline in BTUs per unit.

Further Comparisons

In 2010 the United States Environmental Protection Agency introduced the Miles per Gallon of Gasoline-equivalent (MPGe) metric for measuring electric power outputs for electric vehicles like the Nissan Leaf. As illustrated in the chart above, the EPA determined each gallon of gasoline approximates to roughly 33.56-kilowatt hours of power. 

Using this metric the EPA has since been able to evaluate the fuel economy of all vehicles on the market. This label, which states the vehicle's estimated fuel efficiency, is required to be displayed on all light-duty vehicles currently in production. Each year the EPA releases a list of manufacturers and their efficiency rating. If domestic or foreign manufacturers do not meet EPA standards, though, they will incur a tariff upon import or a hefty fine for domestic sales. 

Due to Obama-era regulations introduced in 2014, even more, stringent requirements have been placed on manufacturers to equalize their annual carbon footprint — at least in terms of new cars on the market. These regulations require that the combined average of all of the manufacturers' vehicles must exceed 33 miles per gallon (or its equivalent in BTU). That means for every high-emissions vehicle that Chevrolet produces, it must offset it with a Partial Zero-Emissions Vehicle (PZEV).

This initiative has significantly reduced the emissions of domestic automobile manufacturing and usage since its implementation.