# If we change the product or its unit of analysis, can we keep the old base inventory and claim a reduction under the Greenhouse Gas Protocol Product Standard?

Canonical: https://senseible.earth/answers/product-footprint-unit-of-analysis-change-needs-new-base

No. The Greenhouse Gas (GHG) Protocol Product Standard sets reduction targets per unit of analysis, which cannot change when comparing inventories over time. If a change redefines the unit, the base inventory cannot be recalculated: create a new base inventory and set a new target.

## The rule

All reduction targets for a product inventory are made on the unit of analysis, and the unit cannot change when inventories are compared over time. If an improvement along the life cycle changes the unit of analysis, a new inventory is completed and the company redefines the base inventory and the reduction goal on the new unit. The standard says the base inventory cannot be recalculated in that case.

## When you may recalculate instead

- The standard says the base inventory should be recalculated when changes in activity data, emission factors, data quality or method affect its results, for example redefining attributable processes, collecting better data, or changing allocation or recycling methods.
- The standard says companies should develop a recalculation policy before recalculating, and they are required to disclose the threshold of insignificance above which a change warrants recalculation. The standard's example: a new emission factor with a one percent effect may fall below the threshold.
- If you already set a threshold of insignificance for justified exclusions, the standard says you should use the same one here.
- If an emission factor change reflects a real change in emissions, the base inventory does not need updating. If the factor was updated because it is more complete or less uncertain, recalculation may be warranted.

## What to report

If the base inventory was recalculated, list all the changes. If it was not, report the threshold under which no recalculation was warranted. Either way the updated report includes both the base results and the updated results.

## A threshold test (example numbers)

- Base result: 5.00 kilograms of carbon dioxide equivalent per unit
- A newly published emission factor would make it 5.05: a change of 1%
- Your published policy says 5% is the threshold, so no recalculation; report the 5% threshold and both results

Numbers and the 5% policy are examples.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the energy behind each period's footprint stays dated and checkable. What your unit of analysis is stays your decision.

- [How Senseible checks records](https://senseible.earth/trust)
- [Reporting a product footprint reduction](https://senseible.earth/answers/product-footprint-reduction-percentage-and-increases)
- [Product footprint target and offsets](https://senseible.earth/answers/product-footprint-target-whole-life-cycle-and-offsets)

Sources: [GHG Protocol Product Life Cycle Accounting and Reporting Standard, chapter 14 Setting Reduction Targets and Tracking Inventory Changes](https://ghgprotocol.org/sites/default/files/standards/Product-Life-Cycle-Accounting-Reporting-Standard_041613.pdf)

Last reviewed 2026-11-04. Wording is from the 2011 Product Standard. Ask your verifier whether a design change alters your unit of analysis before you claim a reduction.