What Are Carbon Factors?

Carbon factors (or “emissions factors”) are numbers used to estimate how much greenhouse gas is released by a given activity. Whether you’re flying from London to New York, heating a building, or printing a press release, each of those actions has an associated carbon cost. Carbon factors translate activity data, like kilometres travelled, kilowatt hours used, or kilograms of material purchased, into estimated carbon emissions (usually expressed in kilograms or tonnes of CO2e).

These factors are the backbone of any carbon calculator, and they allow us to generate standardised, comparable emissions data across activities, timeframes, and organisations.

Why Do We Update Carbon Factors?

Carbon factors are updated regularly to reflect:

• New scientific understanding of emissions

• Changes in technology (e.g., more fuel-efficient aircraft or greener electricity grids)

• Shifts in global and regional energy sources

By keeping carbon factors up to date, we ensure that the GCC Calculator reflects the real-world impact of different activities as accurately as possible. For example, the carbon intensity of electricity is decreasing in many countries due to the rise of renewables, so the emissions from heating a building in 2024 might be lower than in 2020, even if energy use is the same.

When Do We Update Carbon Factors?
We update the GCC Calculator’s carbon factors once per year, and we do this all in one go—rather than piecemeal—as soon as updated data is available from all our key sources. We wait until we’ve received all of these so the update is consistent across the tool.

This usually happens around September or October. As a result, there’s a transition period where some users creating reports early in the year (e.g., for 2024) will still be using the previous year’s carbon factors. Once the new factors are in place, any new 2024 reports will use the updated numbers.

This can lead to small variations in results—especially for materials where factors may have changed significantly (for example, paper and card in 2024). It’s important to be aware that the same year’s report could look slightly different depending on whether it was created before or after the update.

Where Do We Get Our Carbon Factors From?

We’re committed to ensuring our Carbon Calculator is always rigorous and as accurate as possible, which means building it on a solid foundation of internationally recognised standards. Our tool aligns with the Greenhouse Gas (GHG) Protocol, to ensure that the results are robust, credible, and compatible with other carbon reporting systems across the sector and beyond.

To power our calculations, we draw carbon factors from some of the most reliable and up-to-date sources available. These include data from the UK Department for Energy Security and Net Zero (formerly DEFRA/BEIS), a gold standard in emissions accounting, as well as international databases such as EcoInvent and Idemat. These sources allow us to provide detailed, category-specific estimates.

How Do Carbon Factor Updates Affect My Reports?

When carbon factors are updated, any draft or in-progress report that uses the affected year will automatically reflect the new factors—until it’s finalised. Once a report is finalised, the totals are locked in.

So What Does This Mean For You?

Keep an eye out for communications from us regarding the switch-over date (e.g. when the new carbon factors go live). This will usually be during the autumn months. To ensure your reports reflect the most accurate and up-to-date data, we recommend holding off on finalising any in-progress reports for the current year until this update is complete. All in-progress reports will be automatically refreshed with the new figures once they go live. If you have any questions about this change, please get in touch with Aoife: aoife@galleryclimatecoalition.org