What is an emission factor?
An emission factor is the amount of greenhouse gas released per unit of activity, such as CO2e per kWh of electricity from a given fuel.
Why it matters
Emission factors are how carbon accounting turns activity into emissions. Litres of fuel, kWh of electricity or tonnes of material are multiplied by the matching factor to give CO2e. Public bodies publish default factors. The US EPA's GHG Emission Factors Hub, for example, draws on eGRID and IPCC data.
For electricity, each fuel or generating technology has its own factor. A grid's carbon intensity at any moment blends those factors, weighted by how much each fuel is generating. For cloud and AI, the factors behind a region decide how much carbon each kWh carries, so they shape every footprint built on them.
An example
Europe's ENTSO-E Transparency Platform separates around twenty production types, including three kinds of hydro, two of wind, and lignite apart from hard coal. Keeping lignite and hard coal apart lets each carry its own factor, which gives a sharper hourly figure than one combined coal line. Each European country carries its own factor table.
How Greenpixie measures it
Greenpixie uses emission factors to build hourly carbon intensity for each grid area:
- each fuel's share of the hour's generation is multiplied by that fuel's factor for the grid area, and the results are added
- every factor table holds a total value and a combustion-only value, so upstream emissions can be reported separately
- in the US, factors are the eGRID subregion factors the EPA publishes, checked against the EPA's own figures
- in the UK and Europe, each fuel in the published generation mix takes its own factor
Where a source publishes a carbon intensity directly, Greenpixie takes that figure as published instead of rebuilding it from fuel factors.