How Do I Pick the Right Emission Factor
After reading this guide, you will be able to:
- Understand why emission factor selection matters and what can go wrong
- Align your factor choice with the reporting framework you are working under
- Evaluate a factor against the key selection criteria: region, time period, technology, system boundary, and unit
- Decide between activity-based and spend-based approaches
- Walk through a complete worked example of selecting a factor for a real material
- Validate your choice before using it in a calculation
- Use Climatiq tools to search, compare, and apply emission factors at scale
Why emission factor selection matters
A mismatch in region, system boundary, time period, or unit can distort results significantly. Picking the wrong factor turns an otherwise solid inventory into an unreliable one. This guide provides a practical framework for selecting, validating, and documenting your choices.
For guidance on which database to use, see our Understanding the Climatiq Database guide. This guide focuses on the next step: once you know which source to work with, how do you pick the right specific factor within it?
Start with your framework
Before searching for emission factors, identify the reporting framework or standard you are working under. The framework narrows the field before you start looking.
| Framework | What it typically requires or recommends |
|---|---|
| GHG Protocol Corporate Standard | Scope-specific factors; Activity-based factors for scope 1 (direct fuel combustion, process emissions, fugitive emissions); location-based and/or market-based for scope 2; spend-based or activity-based for scope 3 |
| Product Carbon Footprint (ISO 14067 or GHG Protocol Product) | Activity-based factors aligned with the product’s life cycle phases; clear system boundaries, allocation rules and data quality, or direct measurements. |
| CSRD / ESRS | GHG Protocol compliant; auditable sources with clear traceability |
| CBAM | Specific default factors for regulated materials (cement, steel, aluminum, fertilizers) |
| Country-specific rules | Some jurisdictions require or recommend specific sources (e.g. DEFRA for UK, ADEME for France) |
If your framework specifies a source or methodology, start there. If it does not, prioritize representativeness and source quality.
Selection criteria
When evaluating a specific emission factor, check these dimensions.
Region
Use a factor that matches the geography where the activity takes place. For electricity, this means the grid mix of the country or sub-region where consumption occurs. For materials, it means the production region.
Country-specific factors are always preferable to continental or global averages. If no country-specific data is available, use a regional average and document it as a data quality limitation. As a final fallback option, utilize an emission factor from a different comparable country.
For electricity, be aware of the distinction between location-based (average grid mix) and market-based (reflecting contractual instruments like RECs or supplier-specific factors) approaches. Your framework will usually specify which to use.
Time period
Emission factors have a reference year. Ideally, the factor’s year should match your reporting period. If the exact year is not available, use the closest available year from the same source. Avoid using a factor that is more than three to five years old without checking whether the underlying activity has changed significantly. Grid decarbonization, for example, can shift electricity factors substantially within a few years.
For spend-based factors, the year mismatch also introduces inflation effects. If your expenditure and your emission factor are from different years, apply an inflation adjustment. Our Procurement endpoint handles this automatically for EXIOBASE, and Climatiq spend-based factors supplied by CEDA and EXIOBASE from 2022 onwards already include built-in inflation adjustments.
Technology and process
Not all production routes for the same material have the same carbon intensity. Steel from a blast furnace BF-BOF has a very different footprint from steel produced in an electric arc furnace (EAF). If your data source offers technology-specific factors and you know which process your supplier uses, use the specific factor. If you do not know, use the market or production mix for the relevant region.
System boundary
Check what is included in the factor’s lifecycle scope:
| Boundary term | What it typically includes | Typical Business Activity |
|---|---|---|
| Cradle-to-gate | Raw material extraction + upstream transportation + manufacturing | Procurement of raw materials and components (scope 3.1), inputs for PCFs |
| Cradle-to-grave | Cradle-to-gate + use phase + end-of-life | Full product lifecycle reporting (e.g. Digital Product Passport, consumer-facing claims) |
| Well-to-tank (WTT) | Upstream fuel extraction and processing only | Upstream emissions from fuel and energy procurement (scope 3.3 FERA) |
| Tank-to-wheel (TTW) | Direct combustion only | Fleet fuel combustion (scope 1), company vehicles |
| Well-to-wheel (WTW) | WTT + TTW combined | Full transport reporting combining fleet operations and fuel supply chain |
| Other | Check this guide to know more about the supported LCA activities | N/A |
Mixing factors with different boundaries in the same calculation without accounting for the difference creates gaps or double-counting. If your factor covers cradle-to-gate only and you need cradle-to-grave, you will need to add use-phase and end-of-life separately.
Functional unit and unit alignment
Ensure the factor’s unit matches your activity data. Common mismatches to watch for:
- Mass vs. volume vs. energy: a fuel factor in kgCO2e/litre is not the same as kgCO2e/kg. Convert using the correct density.
- LHV vs. HHV: fuel emission factors may be based on Lower Heating Value or Higher Heating Value. Mixing these introduces errors of 5-10%.
- Currency year: for spend-based factors, the currency and currency year of the factor must match your expenditure data, or you need to adjust for inflation.
- Per-unit basis: “per kg of product” vs. “per kg of raw material input” can produce very different results for processes with significant waste or by-products.
Source quality
Prefer emission factors from well-maintained, peer-reviewed, or government-published databases with clear documentation, quality assurance processes, and regular update cycles. All sources available through our platform have been vetted by our Science and Data team. For more on how we handle data quality, see our Methodology Hub .
Activity-based vs. spend-based
Before selecting a specific factor, decide whether to use an activity-based or spend-based approach. This determines which sources and factor types are available to you.
| If you have… | Use | Typical sources |
|---|---|---|
| Physical activity data (kg, kWh, km, liters) | Activity-based factors | DEFRA, EPA, ecoinvent, IEA, GLEC, Carbon Minds |
| Expenditure data only (EUR, USD) | Spend-based factors | EXIOBASE, CEDA, Cornerstone/USEEIO |
| Both | Activity-based where possible, spend-based for the rest | Combine sources by scope category |
For a full comparison, see the Activity-Based vs. Spend-Based section of our database overview guide.
Worked example: 500 kg of steel produced in Germany
You need an emission factor for 500 kg of steel used in a manufactured product. Here is how to walk through the selection criteria step by step.
Framework. You are calculating a PCF. This means you need an activity-based, cradle-to-gate factor with documented data quality.
Region. The steel comes from a German supplier. You need a Germany-specific factor, not a European or global average.
Technology. Your supplier uses an electric arc furnace (EAF) with recycled scrap input. If your data source offers a specific EAF factor for Germany, use it. If not, use the German steel production mix, which blends Blast Oxygen Furnace (BF-BOF) and EAF weighted by market share.
System boundary. You need cradle-to-gate (raw material extraction through steel production at the factory gate). Check that the factor does not include use-phase or end-of-life, which would overcount if you are calculating those separately.
Unit. Your BOM specifies 500 kg. The factor should be in kgCO2e per kg of steel. If it is in kgCO2e per tonne, convert accordingly.
Source. ecoinvent provides a dataset “steel production, electric, low-alloyed, DE” that matches all criteria: German geography, EAF technology, cradle-to-gate boundary, per-kg unit. If you do not have access to ecoinvent, sustamize provides German steel factors at the alloy level, and DEFRA provides a UK steel factor that could serve as a proxy with a data quality note.
Calculate. 500 kg x [selected factor in kgCO2e/kg] = total kgCO2e for this component.
Document. Record: source (ecoinvent v3.12), dataset name, region (DE), year, system boundary (cradle-to-gate), technology (EAF), and any assumptions made.
Validating your choice
Once you have selected a factor, you can run these checks before using it in your final calculation. Most of these are already automatically covered by Climatiq.
Unit and conversion sanity check
Recompute a small example by hand. Verify that unit conversions (mass to volume, currency to base year, energy content) are correct. Off-by-a-factor-of-1000 errors (kg vs. tonnes, grams vs. kilograms) are more common than you might expect.
Plausibility check
Compare your result against known ranges or alternative sources. If your calculated footprint for 1 kg of steel is 50 kgCO2e, something is wrong (typical range is 0.5 to 2.5 kgCO2e/kg depending on process and region). Large deviations usually indicate a mismatch in region, boundary, or unit.
Sensitivity test
Swap to a reasonable alternative factor (e.g. a different region, or production mix instead of technology-specific) and see how much the result changes. If a single factor choice swings your total by more than 10%, document the choice carefully and consider collecting better primary data for that input.
Traceability
Ensure you can cite the source, version, year, region, system boundary, and any assumptions for every factor used. This is required for ISO 14067 declarations, audit readiness, and year-on-year comparisons.
Consistency
Apply the same boundary and methodology across similar activities. Do not use a cradle-to-gate factor for one material and a cradle-to-grave factor for another in the same calculation without adjusting for the difference. Do not mix EEIO models (EXIOBASE, CEDA, USEEIO) within the same scope 3.1 assessment.
How Climatiq helps you choose
We provide several routes to finding and applying the right emission factor, depending on how you work.
For full plan details, see the pricing page . For academic and non-profit plans, contact us .
For guidance on which database to use, see our database overview guide.