UK GHG Conversion Factors 2026: What Changed and How It Affects Your Reports

On 11 June 2026 DESNZ and Defra published the UK GHG conversion factors 2026 and the headline number is hard to miss. The location based electricity factor fell by around 26 to 27% compared with 2025. For a portfolio that has not changed a single light bulb a single lease or a single tenant's behaviour that fall alone can make this year's reported emissions look dramatically better than last year's. Reading that improvement as genuine performance without understanding where it actually came from is the single easiest mistake a real estate reporting team can make this cycle.

This guide sets out exactly what changed in the 2026 factors why the electricity fall is not a like for like year on year reduction and what a portfolio needs to do to report it honestly.

Not sure how the 2026 factor update actually affects your reported figures? Sustainify AI helps real estate teams apply the GHG conversion factors 2026 correctly without letting a methodology change masquerade as a performance win.

What actually changed in the 2026 factors

The electricity factor is where almost every material change in this year's release traces back to. Two things happened together. First continued grid decarbonisation: a larger share of generation now comes from renewables with a corresponding fall in gas fired generation which genuinely lowers the average carbon intensity of the grid. Second and less widely understood DESNZ revised the underlying methodology to reduce the historical reporting lag from two years to one meaning the 2026 factors reflect more recent grid data than previous annual updates typically have. Between them the electricity factor fell by roughly 26% with methane down around 26% and nitrous oxide down around 30% within that same figure. Direct fuel combustion factors by contrast barely moved this year. This was an electricity story almost from top to bottom.

That change ripples outward. Every electricity related factor moved with it including electric vehicles rail travel and homeworking calculations since all of them draw on the same underlying grid intensity figure.

Why the electricity fall is not a like for like reduction

This is the point worth reading twice. Because the 2026 methodology folds roughly two years of grid improvement into a single update alongside the underlying methodology correction itself the fall in your reported electricity emissions this year is not purely a reflection of the grid getting cleaner during 2025. Part of it is a genuine environmental improvement. Part of it is simply DESNZ catching the data up faster than it has in previous years. A portfolio that reports a large year on year drop in emissions without separating these two effects is presenting a number that looks like performance but is in a meaningful part a change in method and timing.

This matters enormously for anyone relying on factor versioning to keep historical reporting periods locked and comparable. The 2025 factors should still be applied to 2025 activity data and the 2026 factors to 2026 activity data exactly as the guidance instructs. What changes is how the resulting trend line needs to be explained to anyone reading it since a step change of this size appearing in a single year is unusual enough that stakeholders and assurers will reasonably ask what is behind it.

What this means for year on year comparability

A portfolio building toward SBTi validation a net zero pathway or simply a credible year on year trend needs to separate the factor driven change from genuine operational change this cycle not next year when the question has already been asked and gone unanswered. That means showing explicitly how much of any year on year reduction comes from the new 2026 factors and how much comes from actual efficiency improvements fuel switching or reduced consumption. Where the effect is material annotating or restating the prior year for context without altering the original locked figures gives readers a trend that reflects real performance rather than a step change in method.

It is also worth remembering exactly what the grid factor does and does not touch. This is the location based Scope 2 figure. Market based reporting using contractual instruments such as REGOs or supplier specific residual mix data sits on a different basis entirely and is not automatically pulled along by this update.

Worried your reported improvement this year is mostly a methodology change in disguise? See how Sustainify AI separates genuine performance from GHG conversion factors 2026 driven change in every report.

What moved beyond electricity

Rail emissions factors were also updated this year using current data from the Office of Rail and Road and Transport for London in place of pre pandemic data that had not been refreshed since 2021 a meaningful correction for any portfolio reporting business travel by rail. Within road transport some plug in hybrid vehicle factors fell by around 5 to 6% while certain vans and heavy goods vehicles increased reflecting newer underlying data from the Department for Transport's road freight statistics rather than any single consistent direction across the category. GWP values remain on the same AR5 basis used in the 2024 and 2025 editions so no version change there to account for. A flat file correction was also issued shortly after the June release to fix a small number of values that had initially shown as zero worth checking if any spend based or lower profile factors in your workbook look suspiciously blank.

How to apply this without misleading your own numbers

The practical rule has not changed: use the factor set that matches the year your activity data actually falls in. 2025 consumption uses 2025 factors 2026 consumption uses 2026 factors regardless of which edition happens to be newest when the report is being written. What has changed is the importance of showing your working around the electricity figure specifically. A governed carbon calculation process that records which factor version was applied to which period and can isolate the factor driven portion of any change from the operational portion is what allows a portfolio to present this year's numbers honestly rather than accidentally taking credit for a DESNZ methodology correction. This connects directly to the same calculation lineage discipline that supports SECR GRESB and CSRD reporting more broadly and it matters more this cycle than most given how concentrated the change is in a single input.

A test for your own 2026 reporting

Pull your electricity emissions figure for this reporting period and last side by side. Ask three questions. Can you state in one sentence how much of the difference between the two is the new factor and how much is a genuine change in consumption. If a board member or an assurer asked you that question directly could you answer it from your existing records or would you need to go and calculate it specifically because they asked. Have you kept the prior period's figures locked under the 2025 factors or has anything been silently recalculated using the new set. If any answer gives you pause this year's reporting cycle is the one to fix it in while the cause is still fresh and well documented rather than a mystery two years from now.

Teams working through this cycle often find it useful to review practical carbon accounting guides and sector specific sustainability insights and to compare approaches with peers through a partner programme where relevant. If you are weighing up tools to support this reviewing pricing and learning more about the team behind the platform is a sensible next step before your next reporting cycle closes.

Ready to report this year's numbers without a methodology change taking credit for your work? Talk to Sustainify AI about applying the GHG conversion factors 2026 correctly across your real estate portfolio.

Frequently Asked Questions

When were the UK GHG conversion factors 2026 published? 

DESNZ and Defra published them on 11 June 2026 with a flat file correction issued shortly afterwards to fix a small number of values that had initially shown as zero.

Why did the UK electricity conversion factor fall so much in 2026? 

Two things combined. Continued grid decarbonisation genuinely lowered the average carbon intensity of the grid and a methodology change reduced the historical reporting lag from two years to one pulling more recent grid data into the calculation than previous updates typically captured.

Is the fall in electricity emissions this year a genuine performance improvement? 

Partly but not entirely. Part of the fall reflects real grid decarbonisation and part reflects DESNZ catching the underlying data up faster than usual which means the full year on year change should not be read as pure operational improvement.

Should I use the 2026 factors for 2025 activity data? 

No. Use the factor set that matches the year your activity data actually falls in so 2025 consumption should still use 2025 factors not the most recently published edition.

Did direct fuel combustion factors change significantly in 2026? 

No they remained largely stable this year. Almost all of the material change in the 2026 release traces back to electricity and the categories that depend on it.

What other categories were affected by the electricity change? 

Electric vehicle factors rail travel and homeworking calculations all moved with the underlying grid intensity figure since each depends on the same electricity conversion factor.

Were rail emissions factors updated for reasons unrelated to electricity? 

Yes. Rail factors were refreshed using current data from the Office of Rail and Road and Transport for London replacing pre pandemic data that had not been updated since 2021.

Did the GWP basis change in the 2026 factors? 

No. The 2026 factors continue to use IPCC AR5 GWP values consistent with the 2024 and 2025 editions so there is no version change to account for on that front.

How should a portfolio explain a large emissions drop caused by the 2026 factors? 

By separating the factor driven portion of the change from any genuine operational improvement and stating that split explicitly rather than presenting the combined figure as pure performance to a board or an assurer.

How can real estate teams apply the 2026 factors without misrepresenting their trend line? 

Keep prior reporting periods locked under the factors that applied at the time and build a process that can isolate factor driven change from operational change on request. You can explore how a governed reporting process works or get in touch to discuss your portfolio specifically.