Home Energy Emissions Calculator Formula

Understand the math behind the home energy emissions calculator. Each variable explained with a worked example.

Use the Home Energy Emissions Calculator

Formulas Used

Total Annual CO2

total_tons = (elec_lbs + gas_lbs + oil_lbs + propane_lbs) / 2204.6

Electricity CO2

elec_tons = elec_lbs / 2204.6

Natural Gas CO2

gas_tons = gas_lbs / 2204.6

Oil & Propane CO2

fuel_tons = (oil_lbs + propane_lbs) / 2204.6

Variables

VariableDescriptionDefault
elec_kwhMonthly Electricity(kWh)900
gas_thermsMonthly Natural Gas(therms)40
oil_gallonsAnnual Heating Oil(gallons)0
propane_gallonsAnnual Propane(gallons)0
elec_lbsDerived value= elec_kwh * 12 * 0.92calculated
gas_lbsDerived value= gas_therms * 12 * 11.7calculated
oil_lbsDerived value= oil_gallons * 22.4calculated
propane_lbsDerived value= propane_gallons * 12.7calculated

How It Works

How to Calculate Home Energy Emissions

Home energy emissions come from the fuels used to power and heat your home.

Emission Factors

  • Electricity: 0.92 lbs CO2/kWh (US grid average)
  • Natural Gas: 11.7 lbs CO2/therm
  • Heating Oil: 22.4 lbs CO2/gallon
  • Propane: 12.7 lbs CO2/gallon

    • Formula

    Total CO2 = Sum of (Usage * Emission Factor) for each fuel / 2,204.6

    Worked Example

    A home using 900 kWh/month electricity, 40 therms/month gas, no oil or propane.

    elec_kwh = 900gas_therms = 40oil_gallons = 0propane_gallons = 0
    1. 01Electricity: 900 * 12 * 0.92 = 9,936 lbs CO2
    2. 02Natural Gas: 40 * 12 * 11.7 = 5,616 lbs CO2
    3. 03Total: 15,552 lbs / 2,204.6 = 7.06 metric tons/year

    Frequently Asked Questions

    What is the biggest source of home emissions?

    For most US homes, electricity and natural gas heating are the two largest sources. Switching to renewable electricity can cut home emissions by 40-60%.

    How does the electricity emission factor vary?

    It depends on your regional grid mix. Coal-heavy areas exceed 1.5 lbs/kWh while hydro-heavy regions may be below 0.2 lbs/kWh.

    Does a heat pump reduce emissions?

    Yes. A heat pump is 2-4x more efficient than direct combustion, significantly cutting heating emissions especially with cleaner grid electricity.

    Ready to run the numbers?

    Open Home Energy Emissions Calculator