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Gasoline gallon equivalent (GGE) or gasoline-equivalent gallon (GEG) is the amount of alternative fuel it takes to equal the energy content of one liquid gallon of gasoline. GGE allows consumers to compare the energy content of competing fuels against a commonly known fuel—gasoline. GGE also compares gasoline to fuels sold as a gas (natural gas, propane, hydrogen) and electricity. In 1994, the US National Institute of Standards and Technology (NIST) defined "gasoline gallon equivalent (GGE) means 5.660 pounds of natural gas." Compressed natural gas (CNG), for example, is a gas rather than a liquid. It can be measured by its volume in standard cubic feet (ft³) (volume at atmospheric conditions), by its weight in pounds (lb) or by its energy content in joules (J) or British thermal units (BTU) or kilowatt-hours (kW·h). It is difficult to compare the cost of gasoline with other fuels if they are sold in different units. GGE solves this. One GGE of CNG and one GGE of electricity have exactly the same energy content as one gallon of gasoline. CNG sold at filling stations is priced in dollars per GGE. Using GGE to compare fuels for use in an internal combustion engine is only the first part of the equation whose bottom line is useful work. In the context of GGE, a real world kind of "useful work" is miles per gallon (MPG) as advertised by motor vehicle manufacturers. Substituting one fuel for another in a given engine may start and may do useful work. However getting optimum efficiency from each fuel–engine combination requires adjusting the mix of air and fuel. This can be a manual adjustment using tools and test instruments or done automatically in a multi-fuel vehicle. Fine tuning of the optimum fuel–air mix may be facilitated by using a supercharger or turbocharger. In battery or electric vehicles, calculating efficiency of useful work begins with the charge–discharge rate of the battery pack, generally 80% to 90%. Next is the conversion of potential energy (BTU) of the charge to distance traveled under power. See table below translating retail electricity costs for a GGE in BTU. Note that throughout this article, 'gallon' refers to the US gallon of approximately 3.8 Litres, as opposed to the imperial gallon of approximately 4.5 Litres ==Gasoline gallon equivalent tables== Rates per kWh for residential electricity in the USA range from $0.0728 (Idaho) to $0.166 (Alaska) and $0.2783 (Hawaii).〔(【引用サイトリンク】title=Electricity Prices by State: National Electric Rate Information )〕〔(【引用サイトリンク】title=Average Retail Price of Electricity )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gasoline gallon equivalent」の詳細全文を読む スポンサード リンク
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