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Green Power Equivalency Calculator Methodologies
- Kilowatt-hour conversion
- Passenger vehicles per year
- Gallons of gasoline consumed
- Barrels of oil consumed
- Propane cylinders used for home barbeques
- Railcars of coal burned
- Coal fired power plant for one year
- Home electricity use
UPDATED December 15, 2009. The equivalency calculations for passenger vehicles each year, gallons of gasoline consumed, propane cylinders used for home barbeques, coal fired power plants, and electricity use of average American homes for one year were updated in the calculator.
Kilowatt-hour conversion
The Green Power Equivalency Calculator uses eGRID (Emissions & Generation Resource Integrated Information Database) non-baseload carbon dioxide (CO2) output emission rates when converting kilowatt-hours (kWh) into avoided units of CO2 emissions. Depending on user data input, the calculator uses either the eGRID subregion non-baseload emission rates the U.S. non-baseload emission rate for this calculation.
Calculation
Note: Please refer to the eGRID Web site for individual nonbaseload subregion emissions rates.
7.18 x 10-4 metric tons CO2 / kWh (eGRID2007 Version 1.1, U.S. annual non-baseload CO2 output emission rate, year 2005 data)
Sources
- (EPA 2009) eGRID2007 Version 1.1, U.S. annual non-baseload CO2 output emission rate, year 2005 data, U.S. Environmental Protection Agency, Washington, DC.
Passenger vehicles per year
Passenger vehicles are defined as 2-axle 4-tire vehicles, including passenger cars, vans, pickup trucks, and sport/utility vehicles.
In 2007, the weighted average combined fuel economy of cars and light trucks combined was 20.4 miles per gallon (FHWA 2008). The average vehicle miles traveled in 2007 was 11,720 miles per year.
In 2007, the ratio of carbon dioxide emissions to total emissions (including carbon dioxide, methane, and nitrous oxide, all expressed as carbon dioxide equivalents) for passenger vehicles was 0.977 (EPA 2009).
The amount of carbon dioxide emitted per gallon of motor gasoline burned is 8.89*10-3 metric tons, as calculated in the "Gallons of gasoline consumed" section.
To determine annual greenhouse gas emissions per passenger vehicle, the following methodology was used: vehicle miles traveled (VMT) was divided by average gas mileage to determine gallons of gasoline consumed per vehicle per year. Gallons of gasoline consumed was multiplied by carbon dioxide per gallon of gasoline to determine carbon dioxide emitted per vehicle per year. Carbon dioxide emissions were then divided by the ratio of carbon dioxide emissions to total vehicle greenhouse gas emissions to account for vehicle methane and nitrous oxide emissions.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
8.89*10-3 metric tons CO2/gallon gasoline * 11,720 VMT car/truck average * 1/20.4 miles per gallon car/truck average * 1 CO2, CH4, and N2O/0.977 CO2 = 5.23 metric tons CO2E /vehicle/year
Sources
- EPA (2009). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007. Chapter 3 (Energy), Tables 3-12, 3-13, and 3-14. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-09-004 (PDF) (66 pp, 737K, About PDF)
- FHWA (2008). Highway Statistics 2007. Office of Highway Policy Information, Federal Highway Administration. Table VM-1.
Gallons of gasoline consumed
To obtain the number of grams of CO2 emitted per gallon of gasoline combusted, the carbon content of the fuel per gallon is multiplied by the oxidation factor and the ratio of CO2’s molecular weight to that of carbon. The average carbon content of gasoline is 2,425 grams of carbon per gallon (EPA, 2005) Fraction oxidized to CO2 is 100 percent (IPCC 2006). The ratio of the molecular weight of CO2 to carbon is 44/12.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
2,425 grams C/gallon * 100% oxidation factor * 44 g CO2/12 g C * 1 metric ton/1,000,000 g = 8.89*10-3 metric tons CO2/gallon of gasoline
Sources
- EPA (2005). Emission Facts: Average Carbon Dioxide Emissions Resulting from Gasoline and Diesel Fuel. EPA420-F-05-001. Available at http://www.epa.gov/oms/climate/420f05001.htm.
- IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.
Barrels of oil consumed
Average heat content of crude oil is 5.80 million btu per barrel (EPA 2007). Average carbon coefficient of crude oil is 20.33 kg carbon per million btu (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).
Carbon dioxide emissions per barrel of crude oil were determined by multiplying heat content times the carbon coefficient times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12).
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
5.80 mmbtu/barrel * 20.33 kg C/mmbtu * 44 g CO2/12 g C * 1 metric ton/1000 kg = 0.43 metric tons CO2/barrel
Sources
- EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: Fast Facts 1990-2005. Conversion Factors to Energy Units (Heat Equivalents) Heat Contents and Carbon Content Coefficients of Various Fuel Types. U.S. Environmental Protection Agency, Washington, DC. USEPA #430-R-07-002 (PDF) (2 pp, 216K, About PDF).
- IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.
Propane cylinders used for home barbeques
Propane is 81.8 percent carbon (EPA 2009). Fraction oxidized is 100 percent (IPCC 2006).
Carbon dioxide emissions per pound of propane were determined by multiplying the weight of propane in a cylinder times the carbon content percentage times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12). Propane cylinders vary with respect to size - for the purpose of this equivalency calculation, a typical cylinder for home use was assumed to contain 18 pounds of propane.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
18 pounds/1 cylinder * 0.818 pound C/pound propane* 44 g CO2/12 g C * 1 metric ton/1000 kg = 0.054 metric tons CO2/cylinder
Sources
- EPA (2009). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007. Annex 2, Table A-41. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-09-004 (PDF) (80 pp, 743K, About PDF).
- IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.
Railcars of coal burned
Average heat content of coal in 2005 was 22.68 million btu per metric ton (EPA 2007). Average carbon coefficient of coal in 2005 was 25.34 kilograms carbon per million btu (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).
Carbon dioxide emissions per ton of coal were determined by multiplying heat content times the carbon coefficient times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12). The amount of coal in an average railcar was assumed to be 100.19 short tons, or 90.89 metric tons (Hancock 2001).
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
22.68 mmbtu/metric ton coal * 25.34 kg C/mmbtu * 44g CO2/12g C * 90.89 metric tons coal/railcar * 1 metric ton/1000 kg = 191.5 metric tons CO2/railcar
Sources
- EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: Fast Facts 1990-2005. Conversion Factors to Energy Units (Heat Equivalents) Heat Contents and Carbon Content Coefficients of Various Fuel Types. U.S. Environmental Protection Agency, Washington, DC. USEPA #430-R-07-002 (PDF) (2 pp, 216K, About PDF).
- Hancock (2001). Hancock, Kathleen and Sreekanth, Ande. Conversion of Weight of Freight to Number of Railcars. Transportation Research Board, Paper 01-2056, 2001.
- IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.
Coal fired power plant for one year
In 2005 there were 1,973,625,358 tons of CO2 emitted from power plants whose primary source of fuel was coal (EPA, 2009).
In 2005 a total of 465 power plants that used coal to generate at least 95% of their electricity (EPA, 2009).
Carbon dioxide emissions per power plant were calculated by dividing the number of power plants by the total emissions from power plants whose primary source of fuel was coal. The quotient was then converted from tons to metric tons.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
1,973,625,358 tons of CO2 * 1/465 power plants * 0.9072 metric tons / 1 short ton = 3,850,479 metric tons CO2/power plant
Sources
- EPA (2009). eGRID2007 Version 1.1, year 2005 data. Available at http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html.
Home electricity use
In 2005, there were 111.1 million homes in the United States; of those, 72.1 million were single-family detached homes and 7.6 million were single-family attached homes for a total 79.7 million single-family homes* nationally (EIA 2008). On average, each single-family home consumed 12,773 kWh of delivered electricity (EIA 2008). The national average carbon dioxide output rate for electricity in 2005 was 1,329 lbs CO2 per megawatt-hour (EPA 2009).
Annual single-family home electricity consumption was multiplied by the carbon dioxide emission rate (per unit of electricity delivered) to determine annual carbon dioxide emissions per home.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
12,773 kWh per home * 1,329.35 lbs CO2 per megawatt-hour delivered * 1 mWh/1000 kWh * 1 metric ton/2204.6 lb = 7.70 metric tons CO2/home.
*A single-family home is defined in the U.S. Department of Energy’s Residential Energy Consumption Survey as follows: A housing unit, detached or attached, that provides living space for one home or family. Attached houses are considered single-family houses as long as they are not divided into more than one housing unit and they have independent outside entrance. A single-family house is contained within walls extending from the basement (or the ground floor, if there is no basement) to the roof. A mobile home with one or more rooms added is classified as a single-family home. Townhouses, rowhouses, and duplexes are considered single-family attached housing units, as long as there is no home living above another one within the walls extending from the basement to the roof to separate the units.
Sources
- EIA (2008). 2005 Residential Energy Consumption Survey. Table US-3, Total Consumption by Fuels Used, 2005, Physical Units (PDF) (4 pp, 50K, About PDF).
- EPA (2009). eGRID2007 Version 1.1. U.S. Environmental Protection Agency, Washington, DC.