Compare Your Footprint — Carbon Intelligence Platform

The 2025 edition of DEFRA/DESNZ greenhouse gas conversion factors reduced the UK electricity emission factor by 14.5%, to approximately 0.128 kg CO2e per kWh. If your business reports its carbon footprint year on year, your Scope 2 number just fell — without you changing a single lightbulb.

What changed in the 2025 DEFRA conversion factors

Every year, the Department for Energy Security and Net Zero (DESNZ) and the Department for Environment, Food and Rural Affairs (DEFRA) publish updated greenhouse gas conversion factors for UK organisations. These factors translate activity data — kilowatt-hours of electricity, litres of fuel, kilometres driven — into carbon dioxide equivalent (CO2e) figures.

The 2025 edition, released in June 2025, included some of the sharpest year-on-year reductions in recent memory:

UK grid electricity: Down 14.5%, reflecting the continued decarbonisation of the UK electricity grid as coal is phased out and renewables expand.

Battery electric vehicles (BEVs): Down 16%, also driven by the cleaner grid, since BEV emissions under the location-based method are tied to grid intensity.

Aviation: Reductions of up to 41% for short-haul flights, following a comprehensive revision of the aviation methodology.

The 2026 factors are expected in June 2026 and will likely show a further reduction as the grid continues to decarbonise.

Why this matters for your year-on-year reporting

If your office used exactly the same amount of electricity in 2025 as it did in 2024, your reported Scope 2 emissions will still fall by approximately 14.5%. That looks like an improvement on paper, but it isn’t one you earned — it’s the grid getting cleaner around you.

This distinction matters for three audiences:

Your board or leadership team. A CEO reviewing the annual sustainability report might see a 15% emissions reduction and assume the energy efficiency programme is working. It might be — but the conversion factor change accounts for most or all of the drop. If you don’t separate grid decarbonisation from operational improvement, you’re misleading your own decision-makers.

Your customers requesting Scope 3 data. A customer reviewing your emissions year on year will expect an explanation. A 14.5% drop with no operational change raises questions — either you’ve explained the factor change, or they assume your data is unreliable.

Your future self. Year-on-year comparisons only mean something if you hold the methodology constant. SECR and UK SRS require organisations to explain changes in methodology that affect comparability. Switching to new conversion factors is exactly such a change.

How to handle year-on-year comparisons correctly

1. Always state which conversion factor set you’re using. In your directors’ report or sustainability disclosure, specify the year: “Emissions calculated using DESNZ/DEFRA 2025 conversion factors.” This is a SECR requirement, not optional.

2. Separate grid-driven reductions from operational ones. The cleanest way to do this: recalculate last year’s footprint using this year’s factors (or vice versa). The difference between the two recalculations isolates the factor change from actual energy use changes.

3. Report energy consumption alongside emissions. Total kilowatt-hours of electricity consumed doesn’t change when the emission factor updates. If your kWh figure is flat and your CO2e figure drops, the explanation is the factor — and reporting both makes that transparent.

4. Watch for aviation and BEV impacts. If your business has significant travel emissions, the 41% short-haul aviation reduction and 16% BEV reduction could create large apparent improvements. The same principle applies: separate the factor change from the behaviour change.

What about the 2026 factors?

The 2026 DEFRA/DESNZ conversion factors are expected in June 2026. Given the trajectory of UK grid decarbonisation, a further reduction in the electricity factor is likely, though the magnitude is uncertain.

If you’re starting your reporting cycle now, use the 2025 factors for financial years ending in 2025/26. When the 2026 factors are published, apply them to financial years starting in 2026. CYF updates its factor library when each new edition is released, so the correct set is applied automatically.

For context, UK SMEs emit an average of 15 tonnes of CO2 per year. For an office-based business where Scope 2 electricity is the dominant emission source, the 14.5% factor reduction could represent a 1–3 tonne drop in reported emissions — significant at that scale.

How CYF helps

Compare Your Footprint automatically applies the correct DEFRA/DESNZ conversion factor set for your reporting period. When the 2026 factors are published, CYF will update its factor library — you don’t need to manually check or apply new values. The platform also separates your energy consumption data from your emissions calculations, making the year-on-year comparison transparent by default.

CYF’s benchmark dataset lets you see whether your emissions reduction is in line with sector peers or whether you’re genuinely outperforming — a distinction that matters when the grid is doing the heavy lifting for everyone.

Methodology guidance from Alice Roberts, Head of Methodology at Compare Your Footprint.

Start measuring with the right factors — CYF keeps your conversion factors current so you don’t have to.