Calculations

Here's where we let you peek behind the curtain and see how we came up with all our numbers for our emissions calculator and product emissions pages. Emissions calculations are still not an exact science. Figuring out the emissions profile of just one type of jet engine could be a lifetime of research, so we know watering things down to "airplane trips" is going to have plenty of inaccuracies. But, if you totally disagree with our numbers or have a resource to suggest let us know!

Household Size

Average Household Size = US Population 19988 /US Households 19989

Electricity

• Electricity emissions for one month = ((($ spent on electricity / national average residential revenue per kilowatt hour of electricity10) * emissions per kilowatt hour for CO2, NOx, SO2, CO, VOC, PM2.5, Pb) / number of people in household) * % of non-renewable electricity
• National average cost per kilowatt hour of electricity
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, NOx, SO2, CO, VOC, PM2.5, Pb11 / 1998 total US electricity generation12
• % non renewable energy = 1 - % renewable energy

Natural Gas

• Natural gas emissions for one month =((($ spent on natural gas / national average natural gas price per therm13) * national average emissions pounds per therm for CO2, NOx, SO2, CO, VOC, PM2.5, Pb14) / number of people in household)

Autos

• Your auto emissions for one month = your miles driven * emissions per mile for CO2, NOx, SO2, CO, VOC, PM2.5, Pb
• Emissions per mile for NOx, SO2, CO, VOC, PM2.5 = (1997 light duty gas vehicle emissions15 + 1997 light duty diesel vehicle emissions16) / 1997 passenger car vehicle miles17
• Emissions per mile for Pb = 1997 light duty gas vehicle and motorcycle emissions18/ (1997 passenger car vehicle miles19 + 1997 motorcycle vehicle miles20)
• Auto emissions per mile for CO221

Light Trucks

• Your light truck emissions for one month = your miles driven * emissions per mile for CO2, NOx, SO2, CO, VOC, PM2.5, Pb
• Emissions per mile for NOx, SO2, CO, VOC, PM2.5, Pb = (1997 light duty gas truck emissions22 + 1997 light duty diesel truck emissions23) / 1997 other 2 axle 4 tire vehicle miles24
• Light duty truck emissions per mile for CO225

Airplanes

• Your airplane emissions for one month = your roundtrips * emissions per passenger per round trip for CO2, NOx, SO2, CO, VOC, PM2.5, Pb
• Emissions per passenger per round trip = Average miles per domestic round trip * emissions per person per mile
• Average miles per domestic round trip = 1st quarter 2000 revenue passenger miles26 / (1st quarter 2000 enplanements27 / 2 enplanements per round trip)
• Emissions per person per mile for all emissions except CO2 = (lbs aircraft emissions28 * % of air ton miles non-freight) / passenger miles29
• % of air ton miles non-freight = 1 . (1998 revenue ton miles freight30 / 1998 revenue ton miles31)
• Emissions per person per mile for CO2 = 1998 Commercial air carrier CO2 emissions32 / 1998 revenue passenger miles33

Walking and Biking

All emissions = miles walked or biked * 0!

There are no direct emissions from walking or biking. (Now, the manufacture of your walking shoes, the paving of the bike path, the electricity to power the walk signal at the intersection& that's a different story.)

Products Search & Emissions Calcs

Clothes Washers, Refrigerators, Freezers, Wine Chillers, & Dishwashers

• kWh used per year34 * emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb35 / 1998 total US electricity generation36

Furnaces & Water Heaters(Gas, Oil, LPG)

• Natural Gas

  (kBtu used per year37 * 1000 Btu/kBtu) / (1020 Btu/scf)38 * national average emissions pounds per scf for CO2, NOx, SO2, CO, VOC, PM2.5, Pb.39

• Oil

  (kBtu used per year40 * 1000 Btu/kBtu) / (138,690Btu/gallon)41 * emissions per gallon of oil combustion for CO2, NOx, SO2, CO, VOC, PM2.5, Pb.42

• LPG

  (kBtu used per year43 * 1000 Btu/kBtu) / (90,500Btu/gallon)44 * emissions per gallon of LPG combustion for CO2, NOx, SO2, CO, VOC, PM2.5, Pb.45

Electric Water Heaters

• (kBtu used per year46 * 1000 Btu/kBtu) / (10,500Btu/kWh47) *emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb48 / 1998 total US electricity generation49

Boilers

• Natural Gas

  Btu used per hour50 / 1020 Btu/scf51 * 500 annual hours of use52 * national average emissions pounds per scf for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.53

• Oil

  Btu used per hour54 / 138,690Btu/gallon55 * 500 annual hours of use56 * emissions per gallon of oil combustion for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.57

• LPG

  Btu used per hour58 / 90,500Btu/gallon59 * 500 annual hours of use60 * emissions per gallon of LPG combustion for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.61

Space Heaters & Pool Heaters

• Natural Gas

  Btu used per hour62 / 1020 Btu/scf63 * 500 annual hours of use64 * national average emissions pounds per scf for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.65

• LPG

  Btu used per year66 / 90,500Btu/gallon67 * 500 annual hours of use68 * emissions per gallon of LPG combustion for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.69

Air Conditioners-Room

• Watts used per hour70 / (1000w/kW) * 5040 hours of use per year71 * emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb72 / 1998 total US electricity generation73

Air Conditioners-Central

• Watts used per hour74 / (1000w/kW) * 6600 hours of use per year75 * emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb76 / 1998 total US electricity generation77

Computers, Monitors, Printers, Faxes, Copiers, TV's, VCR's, & DVD Players

• Watts used per hour in sleep mode78 * (1000w/kW) * 8760 hours per year79 * emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb80 / 1998 total US electricity generation81

Lighting-Ballasts

• Watts used per hour82 * (1000w/kW) * 803 hours per year83 * emissions per kilowatt hour for CO2, Nox, SO2, CO, VOC, PM2.5, Pb.
• Emissions per kilowatt hour = 1998 emissions from fossil fuel plants for CO2, Nox, SO2, CO, VOC, PM2.5, Pb84 / 1998 total US electricity generation85

8. US Department of Transportation, Bureau of Transportation Statistics. "Pocket Guide to Transportation." December 1999. http://www.bts.gov/pg.pdf p. 1. (December 5, 2000).
9. Ibid. p. 1.
10. US Department of Energy, Energy Information Administration. "Electric Power Monthly, Table 53: Estimated U.S. Electric Utility Average Revenue per Kilowatthour to Ultimate Consumers by Sector, Census Division, and State, July 2000 and 1999 (Cents)." http://www.eia.doe.gov/cneaf/electricity/epm/html/epmt53p1.html (December 5, 2000).
11. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating Units at U.S. Electric Utilities by Census Division and State, 1998 and 1999 (Thousand Short Tons)." http://www.eia.doe.gov/cneaf/electricity/epav2/html_tables/epav2t24p1.html (December 5, 2000) and US Environmental Protection Agency. "National Air Pollutant Emission Trends 1900-1998." March 2000. http://www.epa.gov/ttn/chief/trends/trends98/trends98.pdf Tables A-1 to A-7. (December 5, 2000).
12. US DOE, EIA. "Electric Power Annual Volume 1, Table A1. Net Generation from U.S. Electric Utilities by Selected Prime Mover, Census Division, and State, 1997 and 1998 (Million Kilowatthours)." http://www.eia.doe.gov/cneaf/electricity/epav1/epav1ta1.html (December 5, 2000).
13. US DOE, EIA. "Historical Natural Gas Annual, Table 4. Average Price of Natural Gas Delivered to U. S. Consumers, 1967-1999 (Dollars per Thousand Cubic Feet)." http://www.eia.doe.gov/pub/oil_gas/natural_gas/data_publications/historical_natural_gas_annual/current/pdf/table_04.pdf (December 5, 2000).
14. US EPA. "Emissions Factors for Criteria Pollutants and Greenhouse Gases from Natural Gas Combustion" Air CHIEF Version 7.0. November 1999. Table 1.4-2.
15. US EPA. Trends 98. Tables A-1 to A-7.
16. Ibid.
17. US DOT, BTS. "Pocket Guide to Transportation." p. 12.
18. US EPA. Trends 98. Tables A-1 to A-7.
19. US DOT, BTS. "Pocket Guide to Transportation." p. 12.
20. Ibid. p. 12.
21. US EPA, National Vehicle and Fuel Emissions Laboratory. "Annual Emissions and Fuel Consumption for an "Average" Passenger Car." April 1997. http://www.epa.gov/otaq/ann-emit.htm (December 5, 2000).
22. US EPA. Trends 98. Tables A-1 to A-7.
23. US EPA. Trends 98. Tables A-1 to A-7.
24. US DOT, BTS. "Pocket Guide to Transportation." p. 12.
25. US EPA, National Vehicle and Fuel Emissions Laboratory "Annual Emissions and Fuel Consumption for an "Average" Light Truck." April 1997. http://www.epa.gov/otaq/ann-emit.htm (December 5, 2000).
26. US Federal Aviation Administration, Office of Airline Information. "Air Traffic Statistics and Airline Financial Statistics, Traffic Domestic Details." August 3, 2000. http://www.bts.gov/oai/indicators/DomMovAgv.html. (December 5, 2000).
27. Ibid.
28. US EPA. Trends 98. Tables A-1 to A-7.
29. US DOT, BTS. "National Transportation Statistics 1999, Table 1-30 U.S. Passenger-Miles (Millions)." http://www.bts.gov/ntda/nts/NTS99/data/Chapter1/1-30.html (December 1, 2000). and US DOT, BTS. "NTS99, Air Carrier Profile." http://www.bts.gov/ntda/nts/NTS99/data/profiles/AIR99.html (December 4, 2000).
30. US DOT, BTS. "NTS99, Air Carrier Profile." (December 4, 2000).
31. Ibid.
32. US EPA. "Inventory Of U.S. Greenhouse Gas Emissions And Sinks: 1990 - 1998, Table 2-8: CO2 Emissions from Fossil Fuel Combustion in Transportation End-Use Sector (MMTCE)." April 2000. http://www.epa.gov/globalwarming/publications/emissions/us2000/energy.pdf (December 4, 2000).
33. US DOT, BTS. "NTS99, Air Carrier Profile." (December 4, 2000).
34. Appliance energy use compiled from Sears http://www.sears.com, Whirlpool http://www.whirlpool.com, Amana http://www.amana.com, Frigidaire http://www.frigidaire.com, General Electric Appliances http://www.ge.com, Maytag Corporation http://www.maytag.com, KitchenAid http://www.kitchenaid.com, California Energy Commission ftp://energy.ca.gov/pub/efftech/appliance/descriptor_files/ , US DOE, EPA Energy Star Products List" http://www.energystar.gov (October 30th, 2000).
35. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating Units at U.S. Electric Utilities by Census Division and State, 1998 and 1999 (Thousand Short Tons). " http://www.eia.doe.gov/cneaf/electricity/epav2/trends98.pdf (December 5, 2000) and US Environmental Protection Agency, "National Air Pollutant Emission Trends 1900-1998." March 2000. http://www.epa.gov/ttn/chief/trends/trends98/trends98.pdf Tables A-1 to A-7 (December 5, 2000)
36. US DOE, EIA. "Electric Power Annual Volume 1, Table A1. Net Generation from U.S. Electric Utilities by Selected Prime Mover, Census Division, and State, 1997 and 1998 (Million Kilowatthours)." http://www.eia.doe.gov/cneaf/electricity/epav1/epav1ta1.html (December 5, 2000).
37. California Energy Commission.
38. US EPA. "Natural Gas Combustion, 1.4.1 General" Air CHIEF Version 7.0. November 1999.
39. US EPA. "Emissions Factors for Criteria Pollutants and Greenhouse Gases from Natural Gas Combustion: Air CHIEF Version 7.0. November 1999. Table 1.4-2.
40. California Energy Commission.
41. ERC. Petroleum Marketing Monthly, DOE/EIA-0380 (00/03).
42. US EPA. "Criteria Pollutant Emission Factors For Fuel Oil Combustion." Air CHIEF Version 7.0. November 1999. Table 1.3-1 and "Emission Factors For Metals From Uncontrolled No. 6 Fuel Oil Combustion." Table 1.3-11.
43. California Energy Commission.
44. US EPA. "Liquified Petroleum Gas Combustion, 1.5.1 General" Air CHIEF Version 7.0. November 1999. (For the sake of simplicity, this is the conversion for 100% propane combustion.)
45. US EPA. "Emission Factors For LPG Combustion." Air CHIEF Version 7.0. November 1999. Table 1.5-1. (Propane emission factors were used for simplification purposes).
46. California Energy Commission.
47. US DOE, EPA. "Energy Star Purchasing Initiative, Simple Savings Calculator Default Assumptions." http://www.epa.gov/appdstar/purchasing/calculators/defvalue.html (Dec 10th, 2000).
48. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating" and "National Air Pollutant Emission Trends 1900-1998."
49. US DOE, EIA. "Net Generation from U.S. Electric Utilities".
50. California Energy Commision.
51. US EPA. "Natural Gas Combustion, 1.4.1 General."
52. This is Airhead's estimated average yearly hours of use (500 hrs/yr).
53. US EPA. Emissions Factors. Table 1.4-2.
54. California Energy Commission.
55. ERC. Petroleum Marketing Monthly.
56. This is Airhead's estimated average yearly hours of use (500 hrs/yr).
57. US EPA. "Criteria Pollutant Emission Factors For Fuel Oil Combustion."
58. California Energy Commision.
59. US EPA. "Liquified Petroleum Gas Combustion, 1.5.1 General."
60. This is Airhead's estimated average yearly hours of use (500 hrs/yr).
61. US EPA. "Emission Factors For LPG Combustion."
62. California Energy Commission.
63. US EPA. "Natural Gas Combustion, 1.4.1 General."
64. This is Airhead's estimated average yearly hours of use (500 hrs/yr).
65. US EPA. Emissions Factors. Table 1.4-2.
66. California Energy Commission.
67. US EPA. "Liquified Petroleum Gas Combustion, 1.5.1 General."
68. This is Airhead's estimated average yearly hours of use (500 hrs/yr).
69. US EPA. "Emission Factors For LPG Combustion."
70. US EPA "Energy Star Products List" http://www.energystar.gov and California Energy Commission.
71. Sudbury Hydro. "Appliance Usage Chart." Averaged monthly hours of use for room air conditioner ((120 + 720 hrs/mo) / (2) * 12 = 5040 hrs/yr). http://shec.com/docs/appl.htm (Dec 10th 2000).
72. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating" and "National Air Pollutant Emission Trends 1900-1998."
73. US DOE, EIA. "Net Generation from U.S. Electric Utilities".
74. US EPA "Energy Star Products List" http://www.energystar.gov and California Energy Commission.
75. Sudbury Hydro. "Appliance Usage Chart." Averaged monthly hours of use for room air conditioner ((240 + 860 hrs/mo) / (2) * 12 = 6600 hrs/yr). http://shec.com/docs/appl.htm (Dec 10th 2000).
76. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating" and "National Air Pollutant Emission Trends 1900-1998."
77. US DOE, EIA. "Net Generation from U.S. Electric Utilities".
78. US DOE, EPA "Energy Star- labeled home electronics" http://www.epa.gov/appdstar/home_electronics/list.html (October 23rd, 2000).
79. This is Airhead's estimated yearly hours of use (24 hrs/day * 365 days/yr = 8760 hrs/yr ).
80. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating" and "National Air Pollutant Emission Trends 1900-1998."
81. US DOE, EIA. "Net Generation from U.S. Electric Utilities".
82. California Energy Commission.
83. Moezzi (1996-97), "Percent of Household Lamps and Lightin Energy Use in Terms of Lamp Wattage" based on data obtained from TPU analysis of lighting energy use in 161 single-family homes in the Pacific Northwest. Table 2.8.
84. US DOE, EIA. "Electric Power Annual Volume 2, Table 24: Estimated Emissions from Fossil-Fueled Steam-Electric Generating" and "National Air Pollutant Emission Trends 1900-1998."
85. US DOE, EIA. "Net Generation from U.S. Electric Utilities".