FreeHVACCalculators

Start here

Loading calculators…

Menu

Heating and Cooling CO₂ Emissions Calculator

Turn your yearly fuel and electricity use into carbon dioxide emissions with the EPA’s emission factors, and see which energy source contributes most.

Method reviewed October 26, 2026. Version 1.0.0. How it works

Your inputs

Unit system

Therms, from your gas bills. If your bill shows ccf or Mcf, 1 ccf ≈ 1.036 therms.

Only the part used for heating and cooling, or your whole bill if you want the whole home.

Pounds of CO₂ per MWh. 771.5 is the U.S. average from EPA eGRID2023; EPA publishes a rate for each eGRID subregion — use yours for a better estimate.

Result

CO₂ per year
3.7metric tons
CO₂-equivalent per year (with CH₄ and N₂O)
3.71metric tons CO₂e

About 3.7 metric tons of CO₂ a year (3.71 t CO₂e including methane and nitrous oxide).

  • Electricity emissions use a grid average for generation; the CH₄ and N₂O part uses the U.S. average rates. Fuel factors are for combustion at your home only, not for producing and delivering the fuel.
CO₂ per year
8,163lb

CO₂ by energy source

Natural gas
5,849lb CO₂
Propane
0lb CO₂
Heating oil
0lb CO₂
Electricity
2,314lb CO₂
Show the working
  1. Natural gas: therms ÷ 10 × 53.06 kg CO₂/MMBtu
    500 ÷ 10 × 53.06 = 2,653 kg
  2. Propane: gallons × 5.72 kg; heating oil: gallons × 10.21 kg
    0 kg + 0 kg
  3. Electricity: MWh × grid lb/MWh × 0.4536 kg/lb
    3 × 771.5 × 0.4536 = 1,050 kg
  4. CO₂e adds CH₄ × 28 and N₂O × 265 (100-year GWP, IPCC AR5)
    3,703 kg CO₂ → 3,711 kg CO₂e

Emission factors used

Fuel factors come from the EPA’s GHG Emission Factors Hub (January 2025):

  • Natural gas: 53.06 kg CO₂ per million BTU (10 therms)
  • Propane: 5.72 kg CO₂ per gallon
  • No. 2 heating oil: 10.21 kg CO₂ per gallon

Electricity uses a grid rate in pounds of CO₂ per MWh. The default is the U.S. average from EPA’s eGRID2023 data, 771.5 lb/MWh; regional rates differ widely, and EPA publishes one for each eGRID subregion.

CO₂ and CO₂-equivalent

Burning fuel and generating electricity also release small amounts of methane and nitrous oxide. CO₂-equivalent adds them using 100-year global warming potentials of 28 for methane and 265 for nitrous oxide, the values the EPA Hub uses. For home heating fuels they add well under 1 % to the CO₂ figure.

The factors cover combustion only. Methane leaked while producing and delivering gas, and refrigerant leaks from air conditioners and heat pumps, are not included.

Worked example

These are the example values the calculator opens with, and the result the engine calculates for them.

Inputs

Natural gas used per year
500
Propane used per year
0 gal
Heating oil used per year
0 gal
Electricity used per year
3,000 kWh
Grid CO₂ rate
771.5

Result

CO₂ per year
3.7 metric tons
CO₂-equivalent per year (with CH₄ and N₂O)
3.71 metric tons CO₂e
CO₂ per year
8,163 lb

About 3.7 metric tons of CO₂ a year (3.71 t CO₂e including methane and nitrous oxide).

Assumptions

  • EPA combustion factors per unit of fuel (natural gas per MMBtu, propane and No. 2 oil per gallon); 10 therms = 1 MMBtu.
  • Electricity: your grid CO₂ rate (U.S. average 771.5 lb/MWh, eGRID2023) per MWh; CH₄ and N₂O at the U.S. average rates.
  • CO₂e uses 100-year GWPs of 28 for CH₄ and 265 for N₂O, as in the EPA Hub.

Limitations

  • Grid emissions vary by region, season and hour; an annual average is an approximation.
  • Upstream emissions (for example methane leaks from gas production and delivery) and refrigerant leaks are not included.

Frequently asked questions

Is a heat pump lower-carbon than a gas furnace?

It depends on your grid and the heat pump’s efficiency. Enter the gas you would use with a furnace, then the kWh a heat pump would use for the same heat, with your regional grid rate, and compare.

Where do I find my regional grid rate?

EPA’s eGRID publishes CO₂ output rates for each subregion, and the EPA GHG Emission Factors Hub lists them in its electricity table. Your utility may also publish its own emission rate.

Why convert therms by dividing by 10?

A therm is 100,000 BTU, so 10 therms is one million BTU — the unit the EPA natural gas factor uses.

Sources

  1. GHG Emission Factors Hub (January 2025) — U.S. Environmental Protection Agency, Center for Corporate Climate Leadership. Table 1: natural gas 53.06 kg CO₂, 1.0 g CH₄ and 0.10 g N₂O per MMBtu; propane 5.72 kg CO₂, 0.27 g CH₄, 0.05 g N₂O per gallon; distillate fuel oil No. 2 10.21 kg CO₂, 0.41 g CH₄, 0.08 g N₂O per gallon. Table 6 (eGRID2023): U.S. average 771.5 lb CO₂, 0.057 lb CH₄, 0.008 lb N₂O per MWh. Table 11: 100-year GWP CH₄ 28, N₂O 265 (IPCC AR5).
  2. Energy explained — British thermal units (Btu) — U.S. Energy Information Administration. 100,000 Btu per therm; 1,036 Btu/ft³ natural gas; 91,452 Btu/gal propane; 138,500 Btu/gal heating oil; 3,412 Btu/kWh.

Spotted an error? Report a problem with this calculator — see our corrections policy.