Home Energy Carbon Calculator
Most household carbon emissions come from the energy used to power and heat the home. To estimate them you need two things: how much electricity and gas you use in a year, and the carbon intensity of each. This calculator multiplies your electricity use by your grid emission factor and your gas use by the gas emission factor, then adds them. Both factors are editable inputs, so you can drop in the figures from your own provider or national energy agency rather than rely on a hidden assumption.
Home energy carbon formula
Electricity CO2 = electricity kWh * electricity factor
Gas CO2 = gas kWh * gas factor
Total CO2 = electricity CO2 + gas CO2
Tonnes = total CO2 / 1,000
Use the same energy unit (kWh) for both fuels and the matching per-kWh factor. If your gas bill is in therms or cubic metres, convert to kWh first or enter a factor expressed per your bill's unit and adjust the usage to match.
Reducing home energy carbon
- A cleaner electricity tariff or on-site solar lowers the electricity factor directly.
- Improving insulation and heating efficiency reduces gas use.
- Switching from gas heating to an efficient heat pump shifts load to electricity, which pays off most on a clean grid.
- Confirm your provider's published carbon intensity each year, as the grid mix changes.
Home energy carbon: frequently asked questions
How do I calculate my home energy carbon footprint?
Multiply your annual electricity use in kilowatt-hours by your grid emission factor, and your natural gas use by the gas emission factor, then add the two. This calculator keeps both emission factors as editable inputs so you can match the figures published by your electricity provider or national energy agency.
What is a natural gas emission factor?
It is the CO2 released per unit of gas burned. The US EPA publishes a figure of about 0.0053 metric tons of CO2 per therm of natural gas, which is roughly 53 kg per hundred therms. National agencies publish equivalent figures per kWh or per cubic metre. Enter the figure and unit that match your bill.
Where do I find my grid emission factor?
Many electricity providers publish a carbon intensity figure (kg CO2 per kWh) on their website or bills, and the US EPA eGRID database gives regional figures. It varies with the local generation mix, so a renewables-heavy grid has a much lower factor than a coal-heavy one.
Does this include heating oil or propane?
Not directly. This calculator covers electricity and natural gas. If you heat with oil or propane, you can convert that fuel's annual energy to kWh and add it through the gas field using the matching emission factor, or treat the gas field as a generic second fuel.
Official sources
- U.S. Environmental Protection Agency: Greenhouse Gas Equivalencies: calculations and references.
- U.S. Environmental Protection Agency: eGRID emission factors.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.