Calculator Methodology Details

BEF uses information from published and reviewed resources to formulate calculations in the residential carbon footprint calculator found on this website.



INTRODUCTION

The average American household greenhouse gas emissions are 48 metric tons (or 105,840 pounds) each year just from home energy, cars, flights, food and consumer choices. SOURCE: Jones, Kammen "Quantifying Carbon Footprint Reduction Opportunities for U.S. Households and Communities" ES&T, 2011, 45 (9), pp 4088–4095 DOI: 10.1021/es102221h



ELECTRICITY USE

BEF uses information from the U.S. Environmental Protection Agency and Energy Information Administration to calculate the GHG emissions associated with your energy use based on your region (including electricity, natural gas and fuel oil).

The average U.S. home electricity use is 10,837 kilowatt-hours per year. SOURCE: U.S. Energy Information Administration website, www.eia.gov



DRIVING EMISSIONS CALCULATION

We use the most current information from the U.S. Department of Energy’s Fuel Economy standards as well as the Department of Transportation standards to allow you to calculate your automobile’s annual GHG emissions. If you aren’t choosing your specific vehicle or do not know your vehicle’s fuel economy, we use national averages.



AIR TRAVEL EMISSIONS CALCULATION

The BEF air emissions calculation uses your total passenger miles and number of flights to determine an average flight length. From there, we use Defra/DECC’s GHG Conversion Factors for air travel (including conversion factors that account for radiative forcing) to calculate the GHG emissions of your flights.

Radiative Forcing—At high altitudes, the effect of greenhouse gases is considerably different from ground level. Also, aircraft emit water vapor during flight which can cause the formation of ice clouds, called contrails. Where contrails persist, cirrus clouds begin to form, having an additional impact on global warming. Clouds can have a double effect on radiation: they warm the earth by reducing the amount of radiation that escapes into space, but also cool the earth by reflecting the sun's rays back into space. However, contrails lead to a net warming factor, which is estimated to be 2.7 times the normal effect (IPCC, 1999). SOURCE: carbonfund.org/individuals