DEFRA conversion factors 2026 — what changed and what it means for SECR filers

DEFRA (working with DESNZ) publishes a refreshed set of UK greenhouse gas conversion factors every year. These are the numbers you multiply your energy and activity data by to get tonnes of CO2 equivalent (tCO2e) — so when they change, your reported emissions can change even if nothing about your operations did. This post covers what the 2026 set changes, why it matters for your SECR disclosure, and how to apply it cleanly.

What changed

The headline movement most filers care about is the UK grid electricity factor, which feeds your scope 2 (location-based) figure.

The grid electricity factor that feeds your scope 2 (location-based) figure is revised in each annual update, continuing the multi-year downward trend as the UK grid decarbonises. Take the exact 2026 value from the published dataset rather than carrying last year's number forward, and apply the vintage that matches your reporting period.

Refrigerant (F-gas) factors are also revised most years. If you operate air-conditioning or refrigeration plant and report fugitive emissions, check whether the factors for the gases you use — for example R-410A or R-32 — have moved, and re-run those lines.

You can download the official dataset and methodology paper from the UK government greenhouse gas reporting conversion factors page.

Why it matters for SECR

SECR requires you to report your UK energy use and the associated emissions using a recognised, consistent methodology. The DEFRA factors are the de-facto standard. Two practical consequences follow from an annual factor update:

• Your scope 2 location-based emissions can fall (or rise) year-on-year purely because the grid factor moved — not because you used less electricity. If you do not explain this in your narrative, a reader will wrongly credit you with a reduction you did not earn.
• Your intensity ratio (emissions per unit of activity) inherits the same effect. Flag the methodology change so year-on-year comparisons stay honest.

For a refresher on how the factors sit inside the wider calculation, see our guide to scope 1 and scope 2 emissions.

How to apply the change in your next filing

1. Identify your reporting year and use the matching factor vintage. A financial year ending 31 March 2026 generally uses the factor set in force for that year — confirm the correct vintage rather than defaulting to "the newest".
2. Re-run scope 1 (fuel combustion, fleet, F-gas) and scope 2 (purchased electricity, location-based and market-based) against the updated factors.
3. Recalculate your intensity ratio on the same basis.
4. Add a methodology note recording which factor year you used and any restatement of prior figures.

Common mistakes to avoid

• Mixing factor years. Use one vintage across the whole disclosure.
• Claiming an unearned reduction. A grid-factor fall is not an operational improvement — say so.
• Forgetting F-gas. Refrigerant factor changes are easy to miss and can be material for property and manufacturing portfolios.

Need help applying this to your SECR filing? Book a 15-minute call or see the SECR reporting service — £3,500 fixed fee, 21-day audit-ready guarantee.