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Green Power Partnership

Green Power Equivalency Calculator Methodologies

UPDATED February 2014. 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 Green Power Equivalency 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). For that reason, the Equivalencies Calculator uses a non-baseload emission rate.

Emission Factor

6.8927 × 10-4 metric tons CO2 / kWh
(eGRID, U.S. annual non-baseload CO2 output emission rate, year 2010 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 eGRID Year 2010 GHG Annual Output Emission Rates (PDF) (1 pg, 312K, About PDF)).
Sources
  • (EPA 2014). eGRID, U.S. annual non-baseload CO2 output emission rate, year 2010 data. U.S. Environmental Protection Agency, Washington, DC.

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Passenger vehicles per year

In 2011, the weighted average combined fuel economy of cars and light trucks combined was 21.4 miles per gallon (FHWA 2013). The average vehicle miles traveled in 2011 was 11,318 miles per year.

In 2011, the ratio of carbon dioxide emissions to total greenhouse gas emissions (including carbon dioxide, methane, and nitrous oxide, all expressed as carbon dioxide equivalents) for passenger vehicles was 0.988 (EPA 2013a, EPA 2013b).

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 × 11,318 VMT car/truck average × 1/21.4 miles per gallon car/truck average × 1 CO2, CH4, and N2O/0.988 CO2 = 4.75 metric tons CO2E /vehicle/year

Sources

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Miles driven by the average passenger vehicle

Passenger vehicles are defined as 2-axle 4-tire vehicles, including passenger cars, vans, pickup trucks, and sport/utility vehicles.

In 2011, the weighted average combined fuel economy of cars and light trucks combined was 21.4 miles per gallon (FHWA 2013). In 2011, the ratio of carbon dioxide emissions to total greenhouse gas emissions (including carbon dioxide, methane, and nitrous oxide, all expressed as carbon dioxide equivalents) for passenger vehicles was 0.988 (EPA 2013a, EPA 2013b).

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 above.

To determine annual greenhouse gas emissions per mile, the following methodology was used: carbon dioxide emissions per gallon of gasoline were divided by the average fuel economy of vehicles to determine carbon dioxide emitted per mile traveled by a typical passenger 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 × 1/21.4 miles per gallon car/truck average × 1 CO2, CH4, and N2O/0.988 CO2 = 4.20 × 10-4 metric tons CO2E /mile

Sources

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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. In the preamble to the joint EPA/Department of Transportation rulemaking on May 7, 2010 that established the initial National Program fuel economy standards for model years 2012-2016, the agencies stated that they had agreed to use a common conversion factor of 8,887 grams of CO2 emissions per gallon of gasoline consumed (Federal Register 2010).

This value assumes that all the carbon in the gasoline is converted to CO2 (IPCC 2006).

Calculation

8,887 grams of CO2/gallon of gasoline =8.887 × 10-3 metric tons CO2/gallon of gasoline

Sources

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Barrels of oil consumed

Carbon dioxide emissions per barrel of crude oil are 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 average heat content of crude oil is 5.80 mmbtu per barrel (EPA 2013). The average carbon coefficient of crude oil is 20.31 kg carbon per mmbtu (EPA 2013). The fraction oxidized is 100 percent (IPCC 2006).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

5.80 mmbtu/barrel × 20.31 kg C/mmbtu × 44 g CO2/12 g C × 1 metric ton/1,000 kg = 0.43 metric tons CO2/barrel

Sources

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Propane cylinders used for home barbeques

Propane is 81.7 percent carbon (EPA 2013). The 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/1,000 kg = 0.024 metric tons CO2/cylinder

Sources

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Pounds of coal burned

The average heat content of coal consumed in the U.S. in 2013 was 21.48 mmbtu per metric ton (EIA 2014). The average carbon coefficient of coal combusted for electricity generation in 2012 was 26.05 kilograms carbon per mmbtu (EPA 2013). The fraction oxidized is 100 percent (IPCC 2006).

Carbon dioxide emissions per pound 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).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

21.48 mmbtu/metric ton coal × 26.05 kg C/mmbtu × 44 kg CO2/12 kg C × 1 metric ton coal / 2,204.6 pound of coal × 1 metric ton/1,000 kg = 9.31 × 10-4 metric tons CO2/pound of coal

Sources

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Railcars of coal burned

The average heat content of coal consumed in the U.S. in 2013 was 21.48 mmbtu per metric ton (EPA 2014). The average carbon coefficient of coal combusted for electricity generation in 2012 was 26.05 kilograms carbon per mmbtu (EPA 2013). The 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.

21.48 mmbtu/metric ton coal × 26.05 kg C/mmbtu × 44 kg CO2/12 kg C × 90.89 metric tons coal/railcar × 1 metric ton/1,000 kg = 186.50 metric tons CO2/railcar

Sources

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Coal-fired power plant emissions for one year

In 2010, a total of 454 power plants used coal to generate at least 95% of their electricity (EPA 2014). These plants emitted 1,729,127,770.8 metric tons of CO2 in 2010.

Carbon dioxide emissions per power plant were calculated by dividing the total emissions from power plants whose primary source of fuel was coal by the number of power plants.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

1,729,127,770.8 metric tons of CO2 × 1/454 power plants = 3,808,651 metric tons CO2/power plant

Sources
  • EPA (2014). eGRID 2010 data. U.S. Environmental Protection Agency, Washington, DC.

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Home electricity use

In 2012, 113.93 million homes in the United States consumed 1,375 billion kilowatt-hours of electricity (EIA 2013a). On average, each home consumed 12,069 kWh of delivered electricity (EIA 2013a). The national average carbon dioxide output rate for electricity generated in 2010 was 1,232.4 lbs CO2 per megawatt-hour (EPA 2014), which translates to about 1,328.0 lbs CO2 per megawatt-hour for delivered electricity, assuming transmission and distribution losses at 7.2% (EIA 2013b).

Annual 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.

12,069 kWh per home × 1,232.4 lbs CO2 per megawatt-hour generated × 1/(1-0.072) MWh delivered/MWh generated × 1 MWh/1,000 kWh × 1 metric ton/2,204.6 lb = 7.270 metric tons CO2/home.

Sources

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Number of wind turbines installed

In 2012, the average nameplatecapacity of wind turbines installed in the U.S. was 1.94 MW (DOE 2013). The average wind capacity factor in the U.S. in 2012 was 31 percent (DOE 2013).

Electricity generation from an average wind turbine was determined by multiplying the average nameplate capacity of a wind turbine in the U.S. (1.94 MW) by the average U.S. wind capacity factor (0.31) and by the number of hours per year. It was assumed that the electricity generated from an installed wind turbine would replace marginal sources of grid electricity.

The U.S. annual non-baseload CO2 output emission rate to convert reductions of kilowatt-hours into avoided units of carbon dioxide emissions is 6.8927 × 10-4, as calculated in the "Electricity reductions" section above.

Carbon dioxide emissions avoided per wind turbine installed were determined by multiplying the average electricity generated per wind turbine in a year by the national average non-baseload grid electricity CO2 output rate (EPA 2012).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

1.94 MW average capacity × 0.31 × 8,760 hours / year × 1,000 kWh/MWh × 6.8927 × 10-4 metric tons CO2/ kWh reduced = 3,631 metric tons CO2/ wind turbine installed

Sources

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Number of garbage trucks of waste recycled instead of landfilled

The carbon dioxide equivalent emissions avoided from recycling instead of landfilling 1 ton of waste are 2.67 metric tons CO2 equivalent per ton, as calculated in the "Tons of waste recycled instead of landfilled" section above.

Carbon dioxide emissions reduced per garbage truck full of waste were determined by multiplying emissions avoided from recycling instead of landfilling 1 ton of waste by the amount of waste in an average garbage truck. The amount of waste in an average garbage truck was assumed to be 7 tons (EPA 2002).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

2.79 metric tons CO2 equivalent /ton of waste recycled instead of landfilled × 7 tons / garbage truck = 19.51 metric tons CO2E /garbage truck of waste recycled instead of landfilled

Sources

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