An emission factor translates activity data—fuel, electricity, distance, mass, refrigerant, or spend—into greenhouse gas emissions. When factors are updated, two identical activities can produce different reported emissions.
That does not mean one calculation is necessarily wrong. It means the inventory needs factor governance strong enough to explain which result is appropriate and why.
A factor is more than a number
For every factor used, record:
- Publisher and dataset name.
- Dataset version or publication date.
- Activity or emissions year represented.
- Geography and technology represented.
- Gas coverage and whether the value is CO2, individual gases, or CO2 equivalent.
- Global warming potential source.
- Unit and conversion applied.
- Boundary, such as combustion-only or life-cycle.
- Date accessed and source link.
- Internal approval status.
The GHG Protocol Corporate Standard FAQs highlights technological, temporal, and geographical representativeness, completeness, and reliability when selecting data. Those attributes should be searchable fields, not notes that disappear inside a spreadsheet.
Match the factor to the reporting objective
The newest factor is not automatically the correct factor for every task. A 2026 inventory may require a factor representing 2026 activity, but that factor may not be published until later. A regulatory program may prescribe a specific dataset. A base-year comparison may require recalculation under an updated method.
Define a policy that answers:
- Which sources have priority for each activity and jurisdiction?
- Which factor vintage applies when current-year data is unavailable?
- When is a proxy allowed, and who approves it?
- When does a factor change trigger base-year recalculation?
- How are market-based electricity factors reviewed?
- How are supplier-specific factors assessed?
Separate factor updates from activity changes
Suppose fuel consumption is unchanged but the published methane or nitrous oxide factor changes. The resulting inventory movement is methodological, not operational.
Run a bridge that separates:
- Change in activity.
- Change in organizational or operational boundary.
- Change in emission factor.
- Change in global warming potential value.
- Correction of prior-period errors.
- Use of improved primary data.
This makes performance discussions more honest. It also helps determine whether a base-year recalculation policy applies.
Use an approved factor library
An approved library should have unique identifiers, effective dates, version status, units, metadata, and a review history. Calculations should reference the identifier rather than copy a value into each workbook.
Never overwrite an old factor. Retire it for future calculations while retaining it for reproducibility. If a result is recalculated, create a new calculation version and preserve the original.
For Canadian organizations, Environment and Climate Change Canada publishes an annual official national GHG inventory and program-specific emission factors and reference values. Confirm that a government factor is intended for your particular corporate or regulatory use before applying it.
Add factor checks to the reporting close
Before sign-off, verify that factors are approved, units match activity data, formulas reference the correct version, source links remain available, and changes from the prior period have been explained.
A reviewer should be able to reproduce the result and answer a basic question: did emissions change because the business changed, or because the accounting inputs changed?
Sources
See how Carbon Impact supports GHG Protocol reporting — from data collection to disclosure.