This calculator is based on the structure of the EPA Personal emissions calculator. We have customized the parameters for Boston as described below. We have also added calculations of the energy benefits of trees plus other information about the roles trees play in urban settings. See the following sections for detailed descriptions of how the numbers are determined for each emissions factor, plus references to the sources for each calculation.

Electricity

Electricity emission factors are categorized by geographic subregion. The emission factor for Boston was determined by averaging all electric power stations under the Boston Edison Co. Utility Service Area name. The emission factor used in this tool is 1.199 lbs CO₂/kwh.  Source: EPA. eGRID Version 2.1 Plant File, 2006.

Typical annual CO₂ emissions are 16,290 pounds per household, assuming approximately 900 kWh per month. Source: EPA. Unit Conversions, Emission factors, and Other Reference Data.

• Local data for Boston electricity rates come from NSTARonline basic service and rates web pages.
• The numbers used for the calculation in this field are: [Your monthly bill - monthly service charge ($6.43)] / the cost per kwh (0.17978) × the emission factor for Boston (1.199) × months in a year (12).

Natural Gas

Carbon coefficient for natural gas: 117 pounds of CO₂/million BTU, or 0.12 pounds per cubic foot of gas. Source: U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004, Annex 2, Table A-30.

"Typical" annual CO₂ emissions of 11,000 pounds per household based on national average monthly consumption of 7,680 cubic feet of gas. Source: U.S. Energy Information Administration 2004. A Look at Residential Energy Consumption in 2001.

• Local data for Boston natural gas rates come from NSTARonline gas prices.
• The numbers used for the calculation in this field are: [Your monthly bill / the cost per 1000 cubic feet of natural gas ($10.06)] × the emission factor for natural gas in the US (120.593 lbs C/mcf) × months in a year (12).

Fuel Oil

Carbon coefficient for distillate fuel (fuel oil): 161.44 pounds of CO₂ per million BTU, or 22.29 pounds per gallon. Source: U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004, Annex 2, Table A-30.

"Typical" annual CO₂ emissions of 14,500 pounds per household based on national average monthly consumption of 55 gallons of oil. Source: U.S. Energy Information Administration 2004. A Look at Residential Energy Consumption in 2001.

• Due to the highly variable nature of fuel oil prices, a fixed price of $3.00 per gallon is used for calculations in this field.
• The numbers used for the calculation in this field are: [Your monthly bill / the cost per gallon of fuel oil ($3.00)] × the emission factor for fuel oil in the US (22.384) × months in a year (12).

Waste Disposal

Estimates of greenhouse gas emission benefits from recycling newspaper, glass, plastic, metal, and magazines were developed using national waste data and life-cycle greenhouse gas emission factors for waste management. Calculations assume that it would be possible for households to recycle 100 percent of all recyclable materials generated as waste. For example, if you indicate that you recycle newspapers, this calculator assumes that you recycle 100 percent of the newspapers you receive.  EPA's annual Characterization Report was the source of per capita waste generation by material type (e.g., newspaper waste generated per person). Source: U.S. Environmental Protection Agency, 2005. Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2003.

Carbon dioxide equivalent emissions associated with household waste management were calculated using the total emissions for landfills (including incineration, landfill gas-to-energy projects, oxidation, and flaring) from EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2004 and the United States population estimates from EPA's annual Characterization Report mentioned above. The emission factors for each material type were developed by EPA and presented in the Agency's report on greenhouse gas emissions from waste management and in the online WAste Reduction Model (WARM). These emission factors take into account the full material life cycle. The emission factor used for recycling materials in this calculator compares greenhouse gas emissions from recycling with those attributable to landfilling. Source: U.S. Environmental Protection Agency, 2006. Solid Waste Management and Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks, EPA530-R-06-004.

• The numbers used for the calculation in the newspaper recycling field are: number of people you counted for your household × average number of pounds of CO₂ equivalent per person per year that could be saved by recycling newspaper (184.3)
• The numbers used for the calculation in magazine recycling field are: number of people you counted for your household × average number of pounds of CO₂ equivalent per person per year that could be saved by recycling magazines (47.7).
• The numbers used for the calculation in glass recycling field are: number of people you counted for your household × average number of pounds of CO₂ equivalent per person per year that could be saved by recycling glass (25.6)
• The numbers used for the calculation in the plastic recycling field are: number of people you counted for your household × average number of pounds of CO₂ equivalent per person per year that could be saved by recycling plastic (46.58)
• The numbers used for the calculation in the aluminum/steel recycling field are: number of people you counted for your household × average number of pounds of CO₂ equivalent per person per year that could be saved by recycling aluminum and steel cans (165.79)

Transportation

Pounds of carbon dioxide equivalent are calculated based on EPA's estimate of the greenhouse gas emissions from a typical passenger vehicle in the United States. Estimates of the typical values for fuel economy and miles driven per week are from the same source. Note that EPA's emissions estimates are lower than estimates obtained through fueleconomy.gov, because EPA's estimates are for tailpipe emissions only. The fueleconomy.gov site estimates emissions over the full fuel lifecycle (including extraction, processing, and transportation of fuel).

• The numbers used for the calculation in this field are: [number of miles driven per year / vehicle fuel efficiency] × pounds of CO₂ emitted per gallon (19.4) × emissions of greenhouse gases other than CO₂ (100/95).

On the Road

Emission factors based on EPA's estimate of the greenhouse gas emissions from a typical passenger vehicle in the United States. The emission factor used for this calculation is 19.4 lbs CO₂/gallon of gasoline burned. Source: Emission Facts: Greenhouse Gas Emissions from a Typical Passenger Vehicle.

• The numbers used for the calculation in this field are: [number of miles driven per year / vehicle fuel efficiency] × pounds of CO₂ emitted per gallon (19.4) × emissions of greenhouse gases other than CO₂ (100/95).

At Home

Heat

Turning down your heating thermostat: Assumes 1 percent savings in energy use for a 1 degree decrease. Assumes thermostat is turned down for 8 hours each night November through March. Source: U.S. DOE. A Consumer's Guide to Energy Efficiency and Renewable Energy, 2005.

• The numbers used for the calculation in this field are: lbs of CO₂ emitted per year × % of energy source allotted to heating × percent fuel consumption decrease per 1 degree decrease in thermostat temperature setting (0.01) × number of degrees thermostat is turned down.

A/C

Turning up thermostat for central air conditioner: Assumes average household electricity use of approximately 900 kWh per month, and that air conditioners account for 16 percent of residential electricity consumption. Source: U.S. Energy Information Administration. End-use Consumption of Electricity.

• The estimate for the percentage of the year a/c is in use comes from personal communications with a number of year-round residents of Boston.
• The numbers used for the calculation in this field are: total electricity emissions × percent emission reduction per degree (0.01) × number of degrees increased × assumed percentage of the year air conditioner is in use (30%).

Replacing 75-watt incandescent light bulbs with 20-watt compact fluorescents

• Assumes that lights are on for 3 hours per day. Source: ENERGY STAR. Cost Estimate for Energy Star Qualified Light Bulbs, 2006.
• The numbers used for the calculation in this field are: number of 75-watt incandescent light bulbs replaced × annual kwh savings per lamp (60) × electricity emission factor (1.199)

Replacing old refrigerator with an ENERGY STAR model

• Assumes old model uses 820 kWh per year; ENERGY STAR model uses 440 kWh per year. Source: ENERGY STAR. Cost Estimate for Energy Star Qualified Refrigerator, 2006.
• The numbers used for the calculation in this field are: (average kWh/year old fridge - average kWh/year new fridge) × electricity emission factor (1.199)

Replacing an old boiler or furnace with an ENERGY STAR model

• Assumes 2000 sq ft house; 300 square feet of glass. Source: ENERGY STAR. Cost Estimate for Energy Star Qualified Furnaces, 2006.
• The calculations in this field are based on: (average MMBtus/year of old model - average MMBtus/year of new model) × heating fuel specific emission factor.

Replacing single-glazed windows with ENERGY STAR windows

From the Efficient Windows web site: The annual energy performance figures shown here were generated using RESFEN for a typical (new or existing) 2000 sq. ft. house with 300 sq ft of window area (15% of floor area). The windows are equally distributed on all four sides of the house and include typical shading (interior shades, overhangs, trees, and neighboring buildings). U-factor, SHGC, and VT are for the total window including frame. The costs shown here are annual costs for space heating and space cooling only. Costs for lights, appliances, hot water, cooking, and other uses are not included in these figures. RESFEN is a computer program for calculating the annual cooling and heating energy use and costs due to window selection and is available from Lawrence Berkeley National Laboratory (windows.lbl.gov/software/resfen).  Source: ENERGY STAR. Methodology based on RESFEN 3.1 calculations performed by Lawrence Berkeley National Laboratory (LBNL), 2005. http://www.efficientwindows.org/energycosts.cfm

• The numbers used for the calculation in this field are: (average single glazed windows annual energy loss (Btu) - Low-e annual energy loss (Btu)) × heating fuel specific emission factor.

Recycling

Calculations assume that it would be possible for households to recycle 100 percent of all recyclable materials generated as waste. The plastic material type used in the calculator includes PET and HDPE, and the metal material type includes aluminum and steel cans.  See "Waste" section for information on sources used to obtain the numbers in this calculation.

The calculations for this section are based on answering yes to the question: are you willing to recycle this material.  Provided with a yes, the calculator then multiplies the number of people in the home by the CO₂ equivalent emissions that would be saved per person by recycling each material.  Newspaper- 184.3 lbs CO₂/yr, magazines- 47.7 lbs CO₂/yr, glass- 25.6 lbs CO₂/yr, plastic- 46.58 lbs CO₂/yr, aluminum/steel cans- 165.79 lbs CO₂/yr.