Home Energy Footprint Calculator

Residential energy emissions are calculated by activity data times emission factor, one fuel at a time. Combustion fuels have nearly fixed factors because their carbon content is known: a therm of natural gas is 100,000 BTU and yields about 5.31 kg CO2, a gallon of number 2 heating oil yields about 10.16 kg, and a gallon of propane about 5.74 kg. Electricity is different. It has no combustion factor of its own, only the average intensity of the generators serving the meter, which the US EPA publishes by subregion in eGRID. The national average sits near 0.42 kg CO2 per kWh, but subregional values run from roughly 0.1 kg in hydro-rich parts of the Pacific Northwest and upstate New York to about 0.9 kg where coal still dominates, so the same 900 kWh month can differ by a factor of eight in emissions. Useful benchmarks: the average US household uses roughly 10,500 kWh of electricity per year and emits on the order of 7.5 metric tonnes of CO2 from home energy alone, separate from transport, food and goods. Normalizing by occupants and by floor area separates two different effects, since larger households share fixed heating and lighting loads and therefore fall on per-person emissions, while larger floor area raises absolute consumption. The main limitations are that these factors are location-based averages rather than hourly or contract-specific values, that they exclude upstream extraction and pipeline methane leakage that can add 10 to 25 percent on a lifecycle basis, and that they assume standard combustion efficiency rather than the condition of a specific furnace.

Household energy accounting grew out of the data collection that followed the 1973 oil embargo. The US Energy Information Administration launched the Residential Energy Consumption Survey in 1978 to establish, for the first time, what American homes actually used and for what end uses; it remains the statistical backbone for national household energy averages. The emission factors themselves come from combustion chemistry work consolidated in the IPCC Guidelines for National Greenhouse Gas Inventories, first published in 1996 and revised in 2006 and 2019, which fixed default carbon contents and oxidation fractions for each fuel. The electricity side required a separate innovation. The EPA created eGRID, the Emissions and Generation Resource Integrated Database, in the late 1990s to attribute power plant emissions to the grid subregions actually serving customers, which made it possible to give a household a defensible electricity factor rather than a single national number. Corporate and personal accounting conventions were then standardized by the Greenhouse Gas Protocol, published by the World Resources Institute and the World Business Council for Sustainable Development in 1998, whose Scope 2 Guidance of 2015 formalized the distinction between location-based and market-based electricity emissions. Consumer-facing tools followed the data: EPA launched Energy Star in 1992 and later published a household carbon footprint calculator built on the same eGRID and fuel factors used here.