Data Quality
Emission Factors Explained: DEFRA, EPA, and Regional Sources
What emission factors are, where they come from, and how to choose the right ones for accurate greenhouse gas calculations.
An emission factor converts an activity — burning diesel, consuming electricity, spending on steel — into CO₂-equivalent. Choosing the right factors is one of the most consequential decisions in carbon accounting.
How Emission Factors Work
Activity Data × Emission Factor = Emissions
Example: 10,000 kWh × 0.233 kg CO₂e/kWh = 2,330 kg CO₂e
Major Sources
- DEFRA (UK): One of the most comprehensive databases, updated annually, covering fuels, electricity, transport, waste, materials
- US EPA: eGRID for electricity, Supply Chain factors for spend-based Scope 3
- National grid factors: Country-specific electricity factors (e.g., Austria's Umweltbundesamt)
- EXIOBASE: For spend-based Scope 3 estimates via input-output models
Choosing the Right Factor
- Geography: Use factors specific to where the activity occurs
- Vintage: Use factors matching your reporting year
- Scope coverage: Know whether upstream (well-to-tank) losses are included
- Unit alignment: Ensure the factor unit matches your data
- Source authority: Prefer government-published or peer-reviewed factors