Emissions for the existing house are plotted on the map, for the address given. The placemarker is color-coded to indicate the amount of emissions, with the actual data shown when the marker is clicked. The primary "bell curve" distribution shown under the Carbon-IQ menu represents the entire population of Home Energy Saver users. These curves can be generated for any zip code.
To arrive at the carbon-dioxide (CO2) emissions for a given home, we multiply the annual energy for each fuel type by the CO2 emissions factor for the respective fuel. Electricity emissions factors are from U.S. EPA's eGRID (Emissions & Generation Resource Integrated Database), which contains emissions and resource mix data for virtually every power plant and company that generates electricity in the United States (US EPA 2009). Natural gas and fuel oil emission factors of 116.83 and 161.08 lbs CO2/million BTU are derived from U.S. DOE (1994), while the LPG emission factor of 137.26 pounds CO2/million BTU is from U.S. DOE (1996).