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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 April 2011. Several of the conversion factors in this calculator have been updated or revised. See the revision history page for more details.
Electricity use (kilowatt-hours)
The Greenhouse Gas Equivalencies Calculator uses the Emissions & Generation Resource Integrated Database (eGRID) U.S. annual non-baseload CO2 output emission rate to convert reductions of kilowatt-hours into avoided units of carbon dioxide emissions. Most users of the Equivalencies Calculator who seek equivalencies for electricity-related emissions want to know equivalencies for emissions reductions from energy efficiency or renewable energy programs. These programs are not generally assumed to affect baseload emissions (the emissions from power plants that run all the time), but rather non-baseload generation (power plants that are brought online as necessary to meet demand).
Emission Factor
6.8956 x 10-4 metric tons CO2 / kWh
(eGRID2010 Version 1.1, U.S. annual non-baseload CO2 output emission rate, year 2007 data)
Notes:
- This calculation does not include any greenhouse gases other than CO2.
- This calculation does not include line losses.
- Individual subregion non-baseload emissions rates are also available on the eGRID Web site.
- To estimate indirect greenhouse gas emissions from electricity use, please use Power Profiler or use eGRID subregion annual output emission rates as a default emission factor (see eGRID2010 Version 1.1 Year 2007 GHG Annual Output Emission Rates (PDF) (1 p, 278K, About PDF).
Sources
- (EPA 2011) eGRID2010 Version 1.1, U.S. annual non-baseload CO2 output emission rate, year 2007 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 8.92*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.
8.92*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 = 5.1 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) (410 pp, 35MB, 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 heat content of the fuel per gallon is multiplied by the kg CO2 per heat content of the fuel. The average heat content per gallon of gasoline is 0.125 mmbtu/gallon and the average emissions per heat content of gasoline is 71.35 kg CO2/mmbtu. (EPA 2010)
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
0.125 mmbtu/gallon * 71.35 kg CO2/mmbtu * 1 metric ton/1,000 kg = 8.92*10-3 metric tons CO2/gallon of gasoline
Sources
- EPA (2010). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. Annex 2 (Methodology for estimating CO2 emissions from fossil fuel combustion), Table A-33 and P. A-61. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-10-006 (PDF) (407 pp, 19MB, About PDF)
- 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 5.81 mmbtu per barrel (EPA 2010). Average carbon coefficient of crude oil is 20.17 kg carbon per mmbtu (EPA 2010). 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.
5.81 mmbtu/barrel * 20.17 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, 190K, About PDF).
- EPA (2010). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. Annex 2 (Methodology for estimating CO2 emissions from fossil fuel combustion), P. A-58. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-10-006 (PDF) (407 pp, 19MB, 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 81.7 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 propane/1 cylinder * 0.817 pound C/pound propane * 0.4536 kilograms/pound * 44 kg CO2/12 kg C * 1 metric ton/1000 kg = 0.024 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) (410 pp, 35MB, About PDF).
- EPA (2010).Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. Annex 2 (Methodology for estimating CO2 emissions from fossil fuel combustion), P. A-65. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-10-006 (PDF) (407 pp, 19MB, 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 2008 was 21.92 mmbtu per metric ton (EIA 2010b). Average carbon coefficient of coal in 2008 was 25.14 kilograms carbon per mmbtu (EPA 2010a). 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.
21.92 mmbtu/metric ton coal * 25.14 kg C/mmbtu * 44g CO2/12g C * 90.89 metric tons coal/railcar * 1 metric ton/1000 kg = 183.65 metric tons CO2/railcar
Sources
- EPA (2008).Inventory of U.S. Greenhouse Gas Emissions and Sinks: Fast Facts 1990-2006. 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-F-08-005 (PDF) (2 pp, 430K, About PDF).
- EPA (2010a).Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. Annex 2 (Methodology for estimating CO2 emissions from fossil fuel combustion), P. A-23-A-24. U.S. Environmental Protection Agency, Washington, DC. U.S. EPA #430-R-10-006 (PDF) (407 pp, 19MB, About PDF).
- EIA (2010b). Receipts, average costs, and quality of fuels.
- 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 2007, a total of 464 power plants used coal to generate at least 95% of their electricity (EPA 2011). These plants emitted 1,866,813,072.1 metric tons of CO2 in 2007.
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.
Calculation
Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.
1,866,813,072.1 metric tons of CO2 * 1/464 power plants = 4,023,304 metric tons CO2/power plant
Sources
- EPA (2011). eGRID2010 Version 1.1, year 2007 data.
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 generated in 2005 was 1,329 lbs CO2 per megawatt-hour (EPA 2011), which translates to 1,422 lbs CO2 per megawatt-hour for delivered electricity (assuming 7 percent in transmission and distribution losses).
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 * 1,383.56 lbs CO2 per megawatt-hour delivered * 1 mWh/1000 kWh * 1 metric ton/2204.6 lb = 8.02 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 (2011). eGRID2010 Version 1.1. U.S. Environmental Protection Agency, Washington, DC.