Data · DESNZ GHG conversion factors 2026
DEFRA emission factors 2026: what actually changed
In the 2026 DEFRA emission factors, now published by DESNZ as the GHG conversion factors 2026, the UK electricity factor fell from 0.17700 to 0.13096 kgCO2e per kWh.
DESNZ’s own major changes report says most of that fall is grid decarbonisation, with a methodology change contributing 6 to 7 of the 26 percentage points.
This page carries the numbers, the split, the file that was withdrawn, the data year that is missing, and which worksheet each activity belongs in.
The shape of the 2026 update
Three things changed, not one
A conversion-factor update is normally a new column of numbers in the same workbook.
The 2026 set is not that: three separate things changed, and each breaks something that used to work.
The file changed. The condensed set was published every year up to 2025 and stopped in 2026, as the 2026 methodology paper records in a single line.
The number changed. UK electricity fell about 26% and transmission and distribution losses about 30%, and every factor derived from electricity moved with them.
The series changed. DESNZ cut the data lag from two years to one, and in doing so skipped a data year: the 2025 set used 2023 data and the 2026 set uses 2025 data.
Before anything else
What the conversion factors are, and who publishes them
The UK government conversion factors for company reporting of greenhouse gas emissions are published every year by the Department for Energy Security and Net Zero, in the GOV.UK conversion factors collection.
The methodology paper notes they were previously known as the guidelines to Defra and DECC’s conversion factors, which is why searches for “DEFRA emission factors”, “BEIS emissions factors” and “DESNZ conversion factors” all look for the same spreadsheet.
They are, in DESNZ’s words, the current official set of UK government conversion factors, suitable for UK-based organisations of all sizes and for international organisations reporting on their UK operations.
The Code of Practice statement says Aether produces them as part of the National Atmospheric Emissions Inventory contract, subcontracted to Ricardo (now part of WSP), and that a steering group meets every November to discuss methodology.
They are free, and published under the Open Government Licence.
DESNZ flags one trap on the publication page itself: these factors are not Defra’s spend-based emissions multipliers, which sit with the UK and England carbon footprint statistics.
If you are choosing a system to apply activity-based factors across an inventory, see the guide to carbon accounting software for questions about factor versions, boundaries and audit trails.
One is activity-based, per kilowatt-hour, litre or kilometre; the other converts spending, and our guide to spend-based emission factors covers when that is acceptable.
| Name you will see | What it is |
|---|---|
| DEFRA emission factors | The historic name; Defra published the earlier sets |
| BEIS emissions factors | The same dataset under the former department |
| DESNZ GHG conversion factors | The current publisher and title |
| Defra spend-based multipliers | A different dataset: emissions per unit of spend |
The number everyone quotes
The −26%, in the actual figures
A percentage is not something you can put in a report, so here are the numbers underneath it.
The UK electricity generation factor is the one used for location-based Scope 2, and Table 9 of the methodology paper gives it for both sets.
| kgCO2e per kWh | 2025 set | 2026 set | Change |
|---|---|---|---|
| Generated (Scope 2, location-based) | 0.17700 | 0.13096 | −26% |
| T&D losses (Scope 3) | 0.01853 | 0.01299 | −30% |
| Consumed, incl. losses (Table 9) | 0.19553 | 0.14396 | — |
Pair −26% with the generation row and nothing else: DESNZ reports T&D losses separately at about −30%, so a reader who puts −26% beside a figure that already includes losses is reconciling two numbers never meant to add up.
The workbook gives generation and losses as separate factors, which sum to 0.14395; Table 9 prints 0.14396 for electricity consumed because it is built from unrounded components.
Report Scope 2 on the generation factor and the losses in Scope 3, as the methodology paper’s ¶3.1 instructs, and the consumed figure never needs to appear.
The 2025 figures, and when that set still applies, are on our page for the 2025 conversion factors.
Your electricity, on both factor sets
Same kilowatt-hours, different factor set: Scope 2 moves by -11.51 tCO2e without any change in what you used.
Computed from DESNZ methodology papers 2025 and 2026, Table 9. Illustrative arithmetic, not a reported figure.
The arithmetic, once
How a conversion factor is applied
Every line of a UK inventory built on these factors is the same sum: activity data multiplied by a factor, divided by 1,000 for tonnes.
The activity data is what you measured: kilowatt-hours from meters and invoices, litres from fuel cards, kilometres from mileage claims, tonne-kilometres from freight records.
The factor is the published multiplier for that activity, in kilograms of CO2e per unit, taken from the set for the year the activity happened.
Take a site that used 100,000 kWh of grid electricity in 2026.
At the 2026 generation factor of 0.13096 that is 13,096 kg, about 13.1 tonnes of location-based Scope 2.
The losses on the way to the meter add 1,299 kg at 0.01299, reported in Scope 3 rather than added to Scope 2.
The same site on the 2025 set would have shown 17,700 kg of Scope 2, which is why a comparison across the two years needs the footnote this page keeps returning to.
Units are where the sum most often breaks: a factor per kWh against data in MWh is out by a thousand, and one per litre against data in cubic metres is out by the same.
Keep the unit column from the workbook beside every factor you copy, and convert the activity data rather than the factor.
| 100,000 kWh used in 2026 | Factor (kgCO2e/kWh) | Result | Scope |
|---|---|---|---|
| Generation | 0.13096 | 13,096 kg | Scope 2 (location-based) |
| T&D losses | 0.01299 | 1,299 kg | Scope 3, category 3 |
| Total, before WTT | — | 14,395 kg ≈ 14.4 t | — |
The correction
What caused the fall: DESNZ’s own split
Coverage of the 2026 update goes wrong in both directions.
One camp reports the fall as pure grid decarbonisation, which overstates it; the other calls it mostly a methodology artefact, which understates it.
DESNZ published the decomposition in the major changes report, row 17, and it opens: “Most of the decrease is attributed to grid decarbonisation between 2023-2024.”
Grid-mix change from 2023 to 2024 accounts for 16 percentage points, and the extra year of data from 2024 to 2025 for 3 more.
“The remaining 6-7pp of the decrease is due to methodological changes, improvements and corrections”: a better treatment of imports and exports, and a fix to a small double-counting issue that affected autogenerators.
So the honest sentence is that the factor fell mostly because the grid got cleaner across two years of data, with the methodology change contributing roughly a quarter of the move.
Not “the grid decarbonised 26% in a year”, because the fall spans two years of grid mix.
And not “it is mostly a methodology change”, because DESNZ puts methodology at six or seven points out of twenty-six.
That two-year span is the single sentence to footnote when you show a 2025-to-2026 electricity comparison to a board, an auditor or an investor.
The consequence few have written up
The 2024 data year that is never published
Cutting the lag from two years to one did not compress the series; it punched a hole in it.
The methodology paper, ¶3.8, says users who do not adjust earlier years should be aware the new method results in a “‘skipping’ of the 2024 data on UK electricity emissions intensity”.
If you report a single year in isolation, it does not affect you.
It affects anyone whose reporting spans the gap: a three-year trend, an intensity ratio tracked over time, a science-based target with a base year before 2024, or a SECR report that shows the prior year beside the current one.
In each case the published series has a step in it that is partly a real change in the grid and partly an artefact of which data year DESNZ used.
Appendix 2 of the methodology paper publishes an updated full time series for electricity and for heat and steam, on the current method.
The Appendix 2 series restates earlier data years on the new method, so its numbers differ from each year’s published set.
Use it to build a consistent trend if you restate, and never quote an Appendix 2 figure as “the 2025 factor”.
- 2025 setBuilt on 2023 data
Two-year lag; published 10 June 2025.
- —No set built on 2024 data
DESNZ calls it a "skipping" of the 2024 data.
- 2026 setBuilt on 2025 data
One-year lag, using Energy Trends; published 11 June 2026.
Source: DESNZ methodology paper 2026, ¶¶3.5–3.8 and Table 7 footnote
The decision this forces
Should you restate your prior years?
DESNZ does not tell you. Its methodology paper, ¶3.7, says users “will need to decide whether they should adjust their previous years’ estimates”, which is “a recommendation or requirement under some GHG reporting standards”.
| Regime | Does it require restatement? | What it does require |
|---|---|---|
| SECR | No, and it does not forbid it | A statement of the methodologies used (¶16 quoted, ¶20F unquoted) and the prior-year comparatives (¶18 and ¶18A, ¶20H) |
| GHG Protocol Corporate Standard | Where your own recalculation policy says the change is significant | A base-year recalculation policy, applied consistently to methodology changes and data improvements |
| UK SRS S2 | No express restatement rule | ¶29(a)(iii)(3): disclose any changes to the measurement approach, inputs and assumptions, and the reasons |
For most UK filers the question resolves on one point: whether electricity is a large enough share of the inventory to breach the significance threshold in their own recalculation policy.
An office-based services business, where purchased electricity dominates Scopes 1 and 2, will usually find that it does.
A manufacturer whose emissions are dominated by process heat and fleet fuel will usually find that it does not, even though the electricity line moved by a quarter.
The test is the threshold you already published, applied as written, not a fresh judgement about whether this change feels material this year.
If you do restate, restate the whole series on one basis and say which source you used; Appendix 2 is the obvious one, because it is DESNZ’s own recalculation.
Whether or not you restate, name the factor set each reporting year used: one line in a methodology note removes the ambiguity.
The failure it prevents is common: a reader sees emissions fall, credits management action, and a statistical revision is quietly claimed as progress.
The file that is no longer there
The condensed set has been withdrawn
Until 2025 DESNZ published three spreadsheets, and the 2025 release recommended the condensed set “for most, and new, users”.
It is not in the 2026 release.
The 2026 methodology paper records the change twice, in ¶2.3 and ¶3.3: “Note that as of 2026, the Condensed set is no longer published”.
The full set has been relabelled from “for advanced users” to “for all users”, and new users are directed to its Introduction worksheet.
DESNZ gives no reason for the withdrawal.
If a page, a supplier or an internal procedure tells you to download the condensed set, it is describing the 2025 release.
| 2026 release | What it is |
|---|---|
| Full set (for all users) | The workbook; start with its Introduction worksheet |
| Flat file (for automatic processing only) | One row per factor; reissued July 2026 |
| Methodology paper | 152 pages |
| Major changes report | 18 pages; every major movement and why |
| Code of Practice statement | Production, governance, release practice |
A correction with a date on it
The flat file was reissued on 31 July 2026
On 31 July 2026 DESNZ republished the flat file, now titled “flat file (for automatic processing only) — updated July 2026”, as the publication page records.
Its reason, verbatim: the reissue “corrects a number of values that were incorrectly reported as 0 rather than left blank where no data were available”.
GOV.UK names the affected factors: well-to-tank emissions from certain hybrid, CNG and LPG cars, and hotel stays in certain countries.
The full set published in June was not revised; those values were correctly blank there.
The risk is narrow but silent: a zero where there should be a blank reads as “no emissions” rather than “no factor”, and nothing downstream flags it.
If you or your software loaded the flat file between 11 June and 31 July 2026, re-ingest the July version and check any line that used those factors.
The year before
What moved in the 2025 set, for reports still on it
A company whose reporting year falls mostly in 2025 is still on the 2025 set, and many 2026 annual reports will be.
The 2025 set was published on 10 June 2025, and its major changes report recorded a 15% fall in the UK electricity factor, “primarily due to less natural gas use in power stations and increase in net imports of electricity”.
So a company comparing 2024 with 2025 on the published sets sees part of the fall in its electricity emissions arrive a year before the 2026 set, before any change of its own.
Air travel moved furthest, down 16% to 42% depending on haul and class, because the factors it replaced rested on 2021 flights with unusually low load factors.
Waste rows fell 27%, most of it from one input: the materials recovery facility figure revised from 3.44 to 1.64 kg per tonne of input.
DESNZ counts a change as major when it moves more than 5% for a Scope 1 or 2 source, or more than 10% for Scope 3, so smaller movements are not listed and have to be read from the workbook itself.
The 2025 factors, row by row, are on the 2025 conversion factors.
| 2025 set vs 2024 | Movement | DESNZ’s reason |
|---|---|---|
| UK electricity | −15% | Less gas in power stations; more net imports |
| Business travel, air | −16% to −42% | 2021 data was COVID-affected, with low load factors |
| Freight flights | −18% to −23% | — |
| UK electricity for EV cars | −13% to −22% | — |
| Water supply | +25% | — |
| Waste rows (MRF) | −27% | MRF factor revised from 3.44 to 1.64 kg per tonne |
| T&D, WTT electricity, fuels, heat and steam | No major change | — |
The first decision
Which year’s conversion factors to use
| Activity mostly in | Factor set | UK electricity (generation) |
|---|---|---|
| 2025 | 2025 set | 0.17700 |
| 2026 | 2026 set | 0.13096 |
| 2027 | 2027 set, expected June 2027 | — |
The most common error in UK carbon reporting is using the wrong year’s set, and in 2026 it became far more expensive.
The methodology paper, ¶1.10, is explicit: “The 2026 GHG Conversion Factors are for use with activity data that falls entirely or mostly within 2026.”
So a 2026 reporting year uses the 2026 set even if the report is written in 2027, and a year ending 31 March 2026, nine months of it in 2025, falls mostly in 2025.
In a normal year the wrong set moves an electricity figure by a few per cent; in 2026 it moves it by about a quarter, enough to change an intensity ratio, a target trajectory and a year-on-year narrative at once.
DESNZ keeps every annual set in the GOV.UK collection, so a prior year can be reported on its own factors: bookmark the collection, not one year’s page.
The next set is expected in June 2027, with no date announced in advance; the Code of Practice statement says the factors are “regularly published in the first half of June”.
The last two came on 10 June 2025 and 11 June 2026.
Non-calendar years are where the rule bites: a year ending 31 March, 30 June or 30 September straddles two sets, and the calculator beside this text counts the days on each side.
An even spread of days is only a proxy, because heating, cooling and seasonal production put more activity in some months than others.
Where monthly data exists, some organisations apply each month’s set to that month’s activity; the rule does not forbid that, and it removes the straddle altogether.
Whichever approach you take, apply it the same way every year and say so in the methodology note.
Calculator
Which year’s set does my period take?
- 2025: 275 of 365 days (75%)
- 2026: 90 of 365 days (25%)
Most of this period falls in 2025, so on an even spread of activity it takes the 2025 set.
UK electricity, generation (location-based Scope 2) in that set: 0.17700 kgCO2e per kWh.
If activity is heavily seasonal, heating in winter for example, the days can mislead: the test is where the activity fell, and monthly data answers it better than the calendar.
Applies DESNZ methodology paper 2026 ¶1.10 (activity “entirely or mostly within” the year) on an even spread of activity; electricity figures from Table 9. A guide to the rule, not advice on your data.
The question everyone actually has
Which worksheet do I use?
The full set runs to dozens of worksheets, and several look as though they cover the same thing. The map below uses the worksheet names and 2026 movements from DESNZ’s major changes report, with scopes as the methodology paper assigns them.
| Activity | DESNZ worksheet | Scope | 2026 movement |
|---|---|---|---|
| Grid electricity at your sites | UK electricity | Scope 2 (location-based) | −26% |
| Network losses on that electricity | Transmission and distribution | Scope 3, category 3 | −30% |
| Upstream of that electricity | WTT – UK electricity | Scope 3, category 3 | −20% generation; −10% T&D |
| Natural gas, oil and other fuels you burn | Fuels | Scope 1 | No major changes |
| Upstream of those fuels | WTT – fuels | Scope 3, category 3 | No major changes (held from 2023) |
| Owned or leased cars and vans, by distance | Passenger vehicles; Delivery vehicles | Scope 1 | Several PHEV segments −5% to −6%; others up 9.5% to 16% |
| Charging electric vehicles | UK electricity for EVs; UK electricity T&D for EVs | Scope 2; T&D in Scope 3 | Cars −23% to −26%; T&D −25% to −40% |
| Rail, coach, taxis, grey fleet | Business travel – land | Scope 3, category 6 | International rail +154% to +156% |
| Flights | Business travel – air | Scope 3, category 6 | No major changes |
| Freight you pay for | Freighting goods | Scope 3, category 4 or 9 | Rigid HGV +18%; artic −6.2% |
| Homeworking | Homeworking | Scope 3, category 7 | Office equipment −31% |
| Refrigerant leaks | Refrigerant & other | Scope 1 | R-511A corrected to 0 (−100%) |
| Water, materials and waste | Water supply; Water treatment; Material use; Waste disposal | Scope 3 | No major changes |
The double-counting rule, stated once. Generation, transmission losses and well-to-tank are three different emissions, not three versions of one: generation is Scope 2, and the other two are Scope 3, as the methodology paper’s ¶3.1 sets out.
Reporting all three is complete; reporting the same kilowatt-hour of generation twice, once from the electricity tab and once from the EV tab, is double counting.
Fuels against vehicle worksheets. Use the fuel worksheet when you have litres and the vehicle worksheet when you only have distance; litres from a fuel card or invoice are the better evidence.
Passenger vehicles against business travel. The first is for vehicles you own or control; journeys in vehicles you do not, including an employee’s own car, sit in business travel.
Delivery vehicles against freighting goods. The first is per vehicle and per kilometre, the second per tonne-kilometre; if you know what was carried and how far, freighting goods is the more accurate line.
Where the workbook cannot help. It holds no spend-based factors, so purchased goods and services by value need the separate spend-based multipliers.
How each worksheet maps onto the three scopes, with UK examples, is set out in our guide to Scope 1, 2 and 3 emissions.
Filter
Route an activity to its worksheet
Pick a scope or a kind of activity, or type what you are measuring: litres, flights, hotel, EV.
15 of 15 shown
- Scope 2 · location-basedGrid electricity at your sitesWorksheet: UK electricity. Activity data: kWh from meters or invoices. 2026 movement −26%.Methodology ¶3.1; major changes row 17
- Scope 3 · category 3Network losses on that electricityWorksheet: Transmission and distribution. Same kWh as the generation line. 2026 movement −30%.Methodology ¶3.1; major changes row 39
- Scope 3 · category 3Upstream of that electricityWorksheet: WTT – UK electricity. Same kWh again, for extraction and delivery of the fuels generators burn. −20% generation, −10% T&D; not updated since 2023.Major changes rows 46–47
- Scope 1Natural gas, oil and other fuels you burnWorksheet: Fuels. Match the unit and the calorific basis your data arrived in; UK gas kWh are generally gross CV. No major changes in 2026.Methodology ¶2.9
- Scope 3 · category 3Upstream of those fuelsWorksheet: WTT – fuels. Same activity data as the Fuels line. Held from the 2023 release.Methodology ¶¶1.16–1.20
- Scope 1Owned or leased cars and vans, by distanceWorksheets: Passenger vehicles; Delivery vehicles. Use when you have kilometres but not litres; litres go on the Fuels worksheet instead.Major changes rows 7–14
- Scope 2 · T&D in Scope 3Charging electric vehicles at your sitesWorksheets: UK electricity for EVs; UK electricity T&D for EVs. Do not also count the same kWh on the site electricity line.Major changes rows 20, 24
- Scope 3 · category 6Rail, coach, taxis and grey fleetWorksheet: Business travel – land. Employee-owned cars used for work sit here, not in Scope 1. International rail +154% to +156%.Major changes rows 1, 4
- Scope 3 · category 6FlightsWorksheet: Business travel – air. Choose the haul and class that match the booking. No major changes in 2026.Major changes report 2026
- Scope 3 · category 4 or 9Freight you pay forWorksheet: Freighting goods, per tonne-kilometre. Rigid HGV average laden +18%; articulated −6.2%.Major changes rows 49–53
- Scope 3 · category 7HomeworkingWorksheet: Homeworking. Office equipment −31% in 2026, mostly the electricity change arriving at once.Major changes row 61
- Scope 3 · category 6Hotel staysWorksheet: Hotel stay, by country and room-night. Held from the 2022 release; some flat-file values were 0 before 31 July 2026.Methodology ¶¶1.16–1.20; GOV.UK update note
- Scope 1Refrigerant leaksWorksheet: Refrigerant & other, per kg of gas lost. R-511A corrected to 0.Major changes row 13
- Scope 3Water, materials and wasteWorksheets: Water supply; Water treatment; Material use; Waste disposal. No major changes in 2026.Major changes report 2026
- Scope 3 · category 1Purchased goods and services by valueNot in this workbook. Spend needs Defra's separate spend-based multipliers, reported as a different method.GOV.UK publication page; Defra carbon footprint statistics
Worksheet names and 2026 movements from the DESNZ major changes report 2026; scopes from the methodology paper 2026, ¶¶1.3, 2.1, 3.1.
A quiet error on gas
Gross versus net calorific value
This error arrives in the right order of magnitude, on a plausible-looking number, and nothing warns you.
The workbook gives fuel factors on both a gross and a net calorific value basis, because most inventory factors are on a net basis and are converted using the calorific values in the methodology paper, ¶2.7.
Gross CV is the laboratory value; net CV is the useful real-world value, and the difference is essentially the latent heat of the water vapour produced.
Take a net-basis factor against a gross-basis gas bill and the result is wrong by that difference.
The rule is to match the basis your data arrived in, which for UK metered gas is almost always gross.
“Natural gas consumption figures quoted in kilowatt hours (kWh) by suppliers in the UK are generally calculated… on a Gross CV basis.”
“Therefore, the emission factor for energy consumption on a Gross CV basis should be used by default… unless your supplier specifically states they have used Net CV basis.”
The other headline numbers
Gas, diesel and petrol: reading the Fuels worksheet
Searchers for the 2026 factors mostly want four numbers: electricity, natural gas, diesel and petrol.
This page quotes the electricity figures because DESNZ prints them in the methodology paper, Table 9, where they can be checked against a named line.
The fuel factors live in the workbook, on the Fuels worksheet, and each fuel appears in more than one unit and on more than one calorific basis.
That is why third-party summaries disagree with each other on “the” gas or diesel factor: they are often quoting different rows of the same sheet.
Road fuels carry a further choice, because UK pump fuel contains biofuel; the methodology paper treats liquid biofuels for transport in its Table 3, and lists 100% mineral diesel separately.
Pick the row that describes the fuel you actually bought, and do not mix a blended row for one site with a mineral row for another.
Take the factor from the full set itself, note the row you used, and keep a copy of the file with the calculation.
The same discipline answers the electricity trap in the other direction: a 2025 figure of 0.17889 kgCO2e per kWh circulates widely, but the 2025 set, read from its own Table 9, publishes 0.17700.
| What you have | Where to look | Watch for |
|---|---|---|
| Gas bill in kWh | Fuels: natural gas | Gross CV, unless the supplier says net (¶2.9) |
| Fuel card or invoice in litres | Fuels: diesel or petrol | The unit, and blended vs 100% mineral fuel |
| Mileage only | Passenger vehicles or Delivery vehicles | Size and fuel type of the vehicle |
| Heating oil, LPG or other fuel deliveries | Fuels | Whether the invoice is in litres, tonnes or kWh |
Where most Scope 2 errors happen
Location-based versus market-based Scope 2
Purchased electricity is the most misreported line in a UK inventory, because the GHG Protocol Scope 2 Guidance sets two legitimate methods that answer different questions.
The location-based method uses the average intensity of the grid where the electricity is used: for UK consumption, the DESNZ generation factor, 0.13096 kgCO2e per kWh in the 2026 set.
The market-based method uses factors carried by contracts and certificates, with a residual mix where no qualifying contract applies.
The conversion factor set is a grid-average dataset, so a market-based figure takes its factors from your supplier, your contracts and a residual mix, not from the workbook.
The Scope 2 Guidance asks for both figures where a company has operations in markets with contractual instruments, but UK SRS S2 requires only the location-based figure (¶29(a)(v), ¶B30) and says an entity “might” disclose market-based (¶B31).
The full comparison, with REGOs and the UK residual mix, is on our page on market-based Scope 2 emissions.
NESO’s live half-hourly grid intensity, published through its data portal, is a different number again: operational, GB-only and not the annual factor, as our page on UK grid carbon intensity explains.
The two Scope 3 lines that travel with electricity
Transmission losses and well-to-tank
Both moved in 2026, by different amounts and for different reasons, and both are often left out of UK inventories altogether.
T&D losses fell from 0.01853 to 0.01299 kgCO2e per kWh, about 30%, steeper than generation itself, according to the major changes report.
They are the emissions from electricity lost between the power station and your meter, and they belong in Scope 3, category 3.
The well-to-tank factors for UK electricity fell about 20% for generation and 10% for T&D.
The caveat matters more than the numbers: DESNZ says these factors had not been updated since the 2023 publication, and that the underlying fuel WTT values were not updated in this cycle either.
That is a legitimate limitation to note in a methodology statement, and the first thing an assurance provider will ask about if the line moves sharply.
| Factor | 2026 change | DESNZ reason |
|---|---|---|
| T&D losses | −30% | New method; grid mix, losses, imports |
| WTT – UK electricity (generation) | −20% | Not updated since 2023 |
| WTT – UK electricity (T&D) | −10% | As above, plus grid losses |
The other 2026 movements
Travel, vehicles, freight and refrigerants
Electricity took the headlines, but some of the larger percentage moves are elsewhere in the major changes report.
| Factor | 2026 change | DESNZ reason (paraphrased) |
|---|---|---|
| International rail | +154% to +156% | Service patterns and rolling-stock use changed from pre-COVID figures |
| Coach | +42% to +43% | New data from a large operator replaced data implying unrealistically high occupancy |
| National rail | −13% | Passenger.km and fleet composition updated from 2021 estimates |
| London Underground | −44% to −45% | Grid emissions and passenger.km changes |
| Light rail and tram | −26% | Grid emissions and passenger.km changes |
| EV cars (UK electricity for EVs) | −23% to −26% | The electricity factor, plus more efficient vehicles |
| MPV, PHEV and BEV | −36% to −37% | Newer models much more efficient, and more of them |
| Sports PHEV cars | +9.5% | New models with higher direct emissions |
| PHEV vans, Class III and average | +16% | Higher g/km among vans registered in 2024 |
| Rigid HGV (>7.5–17 t), average laden | +18% | Lower loading per journey (DfT road freight statistics) |
| Articulated HGV, 50% and 100% laden | −6.2% | Higher loading |
| Homeworking, office equipment | −31% | Not updated since 2022, plus the electricity change |
| R-511A, Kyoto products | −100% (6.9 → 0 kgCO2e/kg) | Blend corrected from R-290/HFC-152a to R-290/E-170 |
An organisation whose European travel is by rail rather than air may see reported travel emissions rise in 2026 while its travel falls.
The defence is the same as everywhere on this page: name the factor set, name the revision, and let the activity data carry the story.
A plug-in hybrid touches all three scopes: fuel burned is Scope 1 if you own or lease the vehicle, electricity charged at your site is Scope 2, and losses and well-to-tank on both are Scope 3.
Charging at a public charger or at an employee’s home moves that electricity out of your Scope 2, because you are not the one buying it.
Freight factors are per tonne-kilometre, so they depend on how full vehicles are; DESNZ traces the HGV rise to DfT road freight statistics.
The homeworking fall is several years of grid decarbonisation arriving at once, and it looks like a behavioural win when it is not one.
R-511A is a correction rather than a new measurement, so a prior-year figure using it was overstated, and restating is straightforwardly right.
The other half of the story
What did not change, and what is frozen
A major changes report is read for what moved; the more useful half is often what did not.
DESNZ records “no major changes this year” for fuels, bioenergy, heat and steam, water, material use, waste disposal, air and sea travel, hotel stays and outside-of-scopes, in the major changes report.
The methodology paper, ¶1.14, explains why some tables stand still: a risk-based approach focuses on high-emitting sources such as electricity, natural gas, waste, road fuels and fleet.
This is the practical reality of a free national dataset maintained on an annual cycle, not a criticism of it.
It does mean a claim of “current published factors” carries different weight depending on which tab it came from.
| Held constant from | Factors |
|---|---|
| 2025 release | Heat and steam; aviation; water supply and treatment; WTT bioenergy; outside of scopes (except UK electricity) |
| 2024 release | WTT passenger vehicles; WTT business travel – land; WTT delivery vehicles and freight |
| 2023 release | WTT fuels; WTT electricity; WTT heat and steam; WTT business travel – air; refrigerants |
| 2022 release | Hotel stay; homeworking (heating); outside of scopes UK electricity |
| 2021 release | Most CH4 and N2O factors, and a list of less common fuels, taxis, motorcycles and shipping |
A detail that matters in assurance
AR5 warming potentials, with exceptions
The methodology paper, ¶1.9, converts methane and nitrous oxide using the IPCC Fifth Assessment Report’s values: 28 for CH4 and 265 for N2O.
DESNZ gives its reason: AR5 is consistent with UNFCCC reporting and the UK inventory, and the newer IPCC methods “have not yet been officially accepted for use under the UNFCCC”.
The set is not uniformly AR5: refrigerants use AR6 values where AR5 values were not available, well-to-tank bioenergy is still on an AR4 basis, and hotel-stay factors mix bases.
So the honest disclosure for an inventory built on DESNZ factors is “AR5, as used in the DESNZ set”, not a claim to have chosen AR5 or the IPCC Sixth Assessment Report values yourself.
Substituting AR6 values for methane and nitrous oxide inside these factors would break their consistency with the set.
The limit of the dataset
UK factors for UK activity
DESNZ says the factors suit UK-based organisations of all sizes and international organisations reporting their UK operations, on the publication page.
The UK electricity factor describes the UK grid, and applying it to electricity used in another country is a common shortcut in a first inventory.
The set does carry overseas electricity factors, in section 10 of the methodology paper, and other publishers, such as the IEA’s emissions factors dataset, publish national grid factors too.
UK SRS S2, ¶B51, points the same way for Scope 3 secondary data: prioritise emission factors that relate to the jurisdiction in which the activity took place.
The UK grid is now cleaner than many it gets applied to, so in 2026 the shortcut became a larger error.
If a system does the conversion for you
Four questions for your carbon accounting software
Most organisations of any size no longer apply these factors by hand, which moves the risk rather than removing it.
Ask for the flat-file ingestion date, not a reassurance: a version loaded before 31 July 2026 has zeros where DESNZ meant blanks.
The wrong answer on year selection, and a common one, is that a platform applies the latest set to everything in the system; in 2026 that silently restates every prior year’s electricity down by about a quarter.
If prior-year figures changed when the 2026 factors loaded, that is a restatement, whether or not anyone decided to make one.
A platform blending DESNZ factors with an international database may mix warming-potential bases, or apply well-to-tank values DESNZ has held since 2023; neither is wrong, and both should be disclosed.
How to compare the tools is covered in our guide to carbon reporting software.
| Ask | The right answer |
|---|---|
| Which flat file are you on? | The July 2026 reissue, with its ingestion date |
| How do you pick the year-set? | By the reporting period of each record |
| Did prior years change when 2026 loaded? | Only by a decision someone recorded |
| Which GWP basis and WTT vintage? | Stated, not discovered |
The conversation this creates
What an assurance provider will ask
A 26% fall in a headline number attracts attention wherever a report is assured, and the questions are predictable.
Which factor set, evidenced. Keep the workbook itself beside the calculation, not a link to a GOV.UK page whose contents change: the flat file at that address on 12 June and on 1 August 2026 are different files.
Whether the fall was explained. A disclosure that credits a 26% electricity fall to efficiency measures, where the factor did the work, misstates the narrative even when the tonnage is right.
Consistency across the series. If you restated, evidence the policy, the threshold and the source; if you did not, evidence that it was a decision taken against that policy.
Completeness. T&D losses and well-to-tank are the most commonly omitted lines, and both moved this year; an inventory with Scope 2 generation and nothing else is incomplete, not conservative.
What to avoid
The recurring conversion-factor errors
| Mistake | Why it is wrong | Fix |
|---|---|---|
| Wrong year-set | In 2026 the wrong set misstates electricity by about a quarter | Match the set to the year the activity falls in (¶1.10) |
| Reading −26% as your own achievement | Two data years of grid change plus a methodology revision | Footnote the factor set and the break wherever you show a trend |
| Net CV against a gross-basis gas bill | UK gas kWh are generally on a gross basis (¶2.9) | Match the basis the data arrived in |
| Blending Scope 2 methods | Location- and market-based answer different questions | Report each on its own terms, side by side |
| Double-counting electricity | Generation, T&D and WTT are three emissions | Generation once in Scope 2; T&D and WTT in Scope 3 |
| Using the pre-July flat file | Some values were 0 instead of blank | Re-ingest the July 2026 version |
| UK grid factor on overseas use | It describes the UK grid only | Use a factor for the grid where the electricity was used |
| Quoting an Appendix 2 figure as a year's factor | Appendix 2 restates the series on the new method | Quote the Table 9 row for the set |
The value-chain side follows the same matching discipline with harder data; our guide to Scope 3 emissions reporting covers business travel, purchased goods and the rest.
GHG reporting in the UK
Who asks for the numbers these factors produce
There is no single UK greenhouse gas reporting law. Four separate routes ask for emissions, and each is usually calculated on this dataset.
| Route | Who it reaches | What it asks for | Status |
|---|---|---|---|
| SECR | Quoted companies at any size; unquoted companies and LLPs that exceed two of £36m turnover, £18m balance sheet, 250 employees | UK energy use, Scope 1 and 2 emissions, an intensity ratio and the methodology, in the directors' report | Law: SI 2008/410 Sch 7, Parts 7 and 7A |
| UK SRS | Listed companies in UKLR 6, 14, 15, 16 and 22 | Scope 1, 2 and 3 under UK SRS S2, reported or explained | FCA final rules (PS26/19), comply or explain, periods from 1 January 2027 |
| Carbon reduction plans | Suppliers bidding for in-scope government contracts above £5m a year | Scope 1, 2 and specified Scope 3 in a published plan | Procurement policy (PPN 006), not a statutory duty |
| CDP | Companies requested by investors or customers, or disclosing on their own initiative | A full inventory in the annual questionnaire | Voluntary disclosure system |
The same inventory can serve all four, if it is built once, on the right year’s set, with the methodology written down.
What differs is the boundary and the scopes each asks for: SECR is UK energy and Scopes 1 and 2, UK SRS S2 adds Scope 3, and a carbon reduction plan names specific Scope 3 categories.
The ESOS energy audit sits alongside them as an energy regime rather than an emissions one; our ESOS Phase 4 page covers it.
Why any of this matters
How the factors feed SECR, UK SRS S2 and CDP
SECR. The factors are published as relevant to the Environmental Reporting Guidelines, including SECR, created by SI 2018/1155.
Under SECR, qualifying companies report energy use and the resulting emissions in the directors’ report, and state the methodology used (Sch 7 ¶16 for quoted companies, ¶20F for large unquoted companies); the methodology line is where the factor set gets named.
The SECR reporting template and the SECR carbon reporting guide show the calculation in a report, and SECR requirements covers who must report.
The same data sits in our sister reference’s SECR guide, its SECR requirements page and its SECR report template.
UK SRS S2. UK SRS S2 requires gross Scope 1, Scope 2 and Scope 3 emissions measured in line with the GHG Protocol Corporate Standard, under ¶29(a)(i)–(ii) of the standard.
It does not name a factor set: ¶B29 requires “emission factors that best represent the entity’s activity” and disclosure of which were used, and the DESNZ set is the natural UK input.
How the rest of the climate standard works is on our UK SRS S2 climate disclosures page, and the wider picture is on UK SRS.
CDP. The same factor choice feeds a CDP response; how responses are scored is on our CDP scores page and the programme is explained in CDP reporting.
ESOS audits sit alongside all three; the ESOS Phase 4 compliance guide covers that regime, and our UK carbon reporting page maps the landscape.
UK SRS S1 and S2 were published by the Department for Business and Trade on 25 February 2026 for voluntary use.
The FCA’s final rules (PS26/19) require listed companies in scope to report against them on a comply-or-explain basis for accounting periods beginning on or after 1 January 2027.
Where to get them
Downloading the official 2026 dataset
There is one authoritative home for these figures, and it is not a third-party summary, including this one.
Start with the major changes report if you already know the dataset; start with the 2026 full set (Excel) and its Introduction worksheet if you are new.
Carbon accounting systems load the 2026 flat file (Excel, July 2026 revision).
Every year is on the GOV.UK collection page, so the 2027 set will appear where you are already looking.
What to take away
Eight lines, and the terms behind them
1. UK electricity went from 0.17700 to 0.13096 kgCO2e per kWh: quote the pair, not just the percentage.
2. The fall is mostly grid decarbonisation; methodology is 6 to 7 of the 26 points.
3. It spans two years of grid change, because the data lag was cut from two years to one.
4. No factor set uses 2024 data; Appendix 2 of the methodology paper has a consistent restated series if you need to cross the gap.
5. The condensed set no longer exists; anything telling you to download it is describing 2025.
6. The flat file was reissued on 31 July 2026; re-ingest it if you loaded it earlier.
7. Use the set for the year the activity falls in, never the submission year: in 2026 that is a quarter of your electricity figure.
8. Whatever else you do, name the factor set each year used.
| Term | Meaning |
|---|---|
| Conversion factor | A published multiplier that turns a unit of activity into kg of CO2e |
| Activity data | The measured quantity: kWh, litres, km, tonne.km, from meters, invoices and records |
| Location-based Scope 2 | Purchased electricity at the average intensity of the grid it came from |
| Market-based Scope 2 | Purchased electricity at the intensity of the contracts you hold |
| T&D losses | Electricity lost between generation and your meter; Scope 3 |
| Well-to-tank (WTT) | Upstream emissions of extracting, refining and delivering a fuel; Scope 3 |
| Gross and net CV | Two conventions for a fuel's energy content; UK gas bills are generally gross |
| Data year | The year of energy statistics a factor is built on, not the year printed on the file |
| GWP | Global warming potential; DESNZ uses IPCC AR5 for methane and nitrous oxide |
| Flat file | The machine-readable set, one row per factor, for carbon accounting software |
Before you file
Six questions on the rules above
Most errors in a UK inventory are not arithmetic.
They are choices made once, early, and repeated every year: the wrong set, the wrong basis, the wrong scope for a line.
The six questions beside this text are the ones those choices turn on.
If any answer surprises you, the section above that sets out the rule is the one to reread before the numbers go into a directors’ report, a CDP response or a sustainability statement.
For the regimes that consume these figures, see the SECR guide, the UK SRS comply-or-explain page and the carbon reduction plan guide.
Self-check
Conversion factors: test yourself
Every answer is from the DESNZ 2026 methodology paper, the major changes report or UK SRS S2, as cited on this page.
Frequently asked
Questions people ask
What changed in the 2026 UK GHG conversion factors?
DESNZ published the 2026 conversion factors on 11 June 2026. The headline change is the UK electricity factor, which fell from 0.17700 to 0.13096 kgCO2e per kWh, about 26%. DESNZ attributes most of the fall to grid decarbonisation: roughly 16 percentage points to changes in the grid mix between 2023 and 2024, 3 points to the extra year of data from 2024 to 2025, and 6 to 7 points to methodological changes, improvements and corrections. Transmission and distribution losses fell about 30%, and factors built on electricity, including electric vehicles, rail and homeworking, moved with them. Three other things changed: the condensed set was withdrawn, the flat file was reissued on 31 July 2026, and the data lag was cut from two years to one, which skipped the 2024 data year.
Who publishes the UK greenhouse gas conversion factors?
The Department for Energy Security and Net Zero publishes them every year. They were issued as the Defra (and later DECC and BEIS) conversion factors in earlier years, which is why most people still search for the DEFRA factors. They are produced by Aether as part of the National Atmospheric Emissions Inventory contract managed by Ricardo, now part of WSP, with WRAP contributing, and they are free under the Open Government Licence.
Which year of conversion factors should I use?
Use the set for the year your activity data falls in, not the year you compile or file the report. DESNZ says the 2026 factors are for use with activity data that falls entirely or mostly within 2026, so a 2026 reporting year uses the 2026 set even if the report is written in 2027. Every earlier set stays in the GOV.UK collection. Applying the 2026 set to 2025 activity would understate electricity emissions by about a quarter.
What is the 2026 UK electricity emission factor?
The UK electricity generation factor in the 2026 set is 0.13096 kgCO2e per kWh, the figure for location-based Scope 2 on UK grid electricity used in 2026. Transmission and distribution losses are a separate 0.01299 kgCO2e per kWh and belong in Scope 3. Together the two workbook factors come to 0.14395; Table 9 of the methodology paper prints 0.14396 for electricity consumed, because it is calculated from unrounded components. Well-to-tank factors are separate again, and also Scope 3.
Is there still a condensed set of DEFRA conversion factors?
No. The condensed set was published up to and including 2025 and was not published in 2026. The 2026 methodology paper says that as of 2026 the condensed set is no longer published, and keeps its old tables only so users can find values from earlier years. The full set is now labelled "for all users", and new users are directed to its Introduction worksheet.
Can I compare my 2026 electricity emissions with 2025?
Only with a caveat. The 2025 set was built on 2023 data and the 2026 set on 2025 data, so the published change contains two years of grid movement plus 6 to 7 percentage points of methodological change, and no published set uses 2024 data. Appendix 2 of the methodology paper publishes an updated time series for electricity on the current method, which is a restated series and not the published factors. DESNZ says users must decide whether to adjust earlier years, by reference to the reporting standard they follow.
What is the difference between location-based and market-based Scope 2?
The location-based method uses the average emissions intensity of the grid where the electricity is used; for UK consumption that is the DESNZ generation factor, 0.13096 kgCO2e per kWh in the 2026 set. The market-based method uses factors carried by contracts and certificates, such as REGO-backed supply, with a residual mix for the rest. The GHG Protocol Scope 2 Guidance asks for both where contractual instruments exist. UK SRS S2 requires the location-based figure and only permits market-based.
How do the conversion factors relate to SECR and UK SRS?
DESNZ publishes the factors as relevant to the Environmental Reporting Guidelines, including SECR, and they are the usual way to turn the kWh and fuel that SECR requires into tonnes of CO2e. UK SRS S2 requires gross Scope 1, 2 and 3 emissions measured under the GHG Protocol Corporate Standard and does not prescribe emission factors; it requires those that best represent the entity's activity, and disclosure of which factors were used.
When will the 2027 DEFRA conversion factors be published?
DESNZ says the next publication is expected in June 2027. It does not announce a release date in advance; its Code of Practice statement says the factors are regularly published in the first half of June. The 2025 set was published on 10 June 2025 and the 2026 set on 11 June 2026. You can sign up on GOV.UK for notifications of updates.
Are the DEFRA emission factors the same as Defra's spend-based multipliers?
No. The conversion factors are activity-based: kilowatt-hours, litres, kilometres, tonnes. Defra separately publishes spend-based emissions multipliers alongside its UK and England carbon footprint statistics. DESNZ says those multipliers are primarily for comparing the carbon intensity of categories of UK demand, but can give an initial assessment of supply-chain emissions from spending. Report which method each line of an inventory used.
What are the BEIS emissions factors?
The same dataset under an earlier department's name. The UK government conversion factors for company reporting have been published by Defra, DECC, BEIS and now DESNZ. A page or procedure that calls them the BEIS factors may be pointing at an old year's set, so check the publication year on the file.
Which factors changed because the flat file was reissued?
DESNZ reissued the 2026 flat file on 31 July 2026 because some values were reported as 0 rather than left blank where no data were available. GOV.UK says the affected factors relate to well-to-tank emissions from certain hybrid, CNG and LPG cars, and hotel stays in certain countries. The full set published in June was not revised.
What changed in the 2025 conversion factors?
In the 2025 set, published on 10 June 2025, the UK electricity factor fell 15%, which DESNZ attributed primarily to less natural gas use in power stations and more net imports of electricity. Business travel by air fell 16% to 42% because the 2021 data behind the old factors was affected by COVID, water supply rose 25%, and several waste rows fell 27% after a materials recovery facility figure was revised from 3.44 to 1.64 kg per tonne.
How do I calculate my carbon footprint from electricity use?
Multiply the kilowatt-hours on your meter readings or invoices by the conversion factor for the year the electricity was used, then divide by 1,000 for tonnes. For 2026 use in the UK, 100,000 kWh at the generation factor of 0.13096 kgCO2e per kWh is 13,096 kg, or about 13.1 tonnes of location-based Scope 2. The same kWh at the transmission and distribution factor of 0.01299 adds 1,299 kg, which is reported in Scope 3. Use the 2025 set for electricity used mostly in 2025.
Do I have to use the DESNZ conversion factors for SECR?
Schedule 7 to SI 2008/410 does not name a factor set. It requires the directors' report to state the methodologies used to calculate the figures, which is where the factor set is named. DESNZ publishes the conversion factors as relevant to its Environmental Reporting Guidelines, including SECR, so they are the usual UK choice, but the legal requirement is disclosure of the method, not a particular dataset.
Was the 2025 UK electricity factor 0.17889?
No. The 2025 set, read from Table 9 of the 2025 methodology paper, gives 0.17700 kgCO2e per kWh for UK electricity generation, so the fall to 0.13096 in 2026 is 26.0%. A figure of 0.17889 and a fall of 26.8% circulate widely, but neither matches the published 2025 set.
Where can I download the DEFRA conversion factors in Excel?
On the GOV.UK page "Greenhouse gas reporting: conversion factors 2026". The factors themselves are published as Excel workbooks: the full set for all users and the flat file for automatic processing, revised in July 2026. The methodology paper and the major changes report are PDFs. Earlier years sit on the GOV.UK collection page for government conversion factors for company reporting.
What is GHG reporting in the UK, and who has to do it?
There is no single UK GHG reporting law. Quoted companies and large unquoted companies and LLPs report energy and emissions in their annual reports under SECR; listed companies in UKLR 6, 14, 15, 16 and 22 must report against UK SRS on a comply-or-explain basis for accounting periods beginning on or after 1 January 2027, under the FCA's final rules in PS26/19; suppliers bidding for major government contracts are asked for carbon reduction plans under PPN 006; and many companies answer CDP. Each asks for emissions, and each is usually calculated with these conversion factors.
Sources
Primary sources
Every figure, date and status on this page traces to the instrument’s owner. Secondary commentary is never the source for a number.
- DESNZGreenhouse gas reporting: conversion factors 2026
Published 11 June 2026, last updated 31 July 2026: the full set, the flat file, the methodology paper and the major changes report.
- DESNZ2026 conversion factors methodology paper, ¶¶1.3–1.20, 2.3, 2.9, 3.1, 3.3–3.8 and Table 9
Scopes, the activity-year rule, the frozen tables, gross vs net CV, the withdrawn condensed set, the lag change and the electricity factors.
- DESNZ2026 conversion factors: major changes report, rows 1–61
Every movement over 5% (Scope 1 and 2) or 10% (Scope 3), with DESNZ's reason, including the −16 / −3 / 6–7pp split.
- DESNZConversion factors 2026: statement of voluntary compliance with the Code of Practice for Statistics
Who produces the factors, the November steering group, and release in the first half of June.
- DESNZUK government conversion factors for company reporting (collection)
Every annual set, so each year is reported on its own factors.
- DESNZGreenhouse gas reporting: conversion factors 2025
Published 10 June 2025; the last release with a condensed set.
- legislation.gov.ukSI 2018/1155 — Directors' Report and LLP (Energy and Carbon Report) Regulations 2018
The instrument that created SECR.
- legislation.gov.ukSI 2008/410 Schedule 7, Parts 7 and 7A (¶¶15–20K)
SECR emissions, methodology (¶16, ¶20F) and comparatives (¶18, ¶18A, ¶20H).
- DESNZEnvironmental Reporting Guidelines, including SECR guidance
The government guidance the factors are published for.
- Department for Business and TradeUK SRS S2 Climate-related Disclosures, ¶29(a)(ii)–(v), ¶¶B29–B31
GHG Protocol measurement, disclosure of methodology changes, emission factors, and location-based Scope 2.
- GHG ProtocolScope 2 Guidance (2015)
Location-based and market-based methods, and dual reporting where contractual instruments exist.
- GHG ProtocolA Corporate Accounting and Reporting Standard (revised edition, 2004)
Scopes 1 and 2, and the base-year recalculation policy that governs restatement.
- DefraUK and England's carbon footprint to 2023 (incl. spend-based emissions multipliers)
The separate spend-based dataset, often confused with these factors.
- NAEINational Atmospheric Emissions Inventory — reports
The UK inventory the factors are derived from.
- DESNZEnergy Trends
The statistics that let DESNZ cut the electricity data lag to one year.
- DESNZDUKES Chapter 5: electricity
Generation mix and grid losses.
- DfTRoad freight statistics
The loading data behind the 2026 HGV movements.
- NESONESO data portal
Live GB grid data — operational, and not the annual DESNZ factor.
- IEAEmissions Factors (country grid factors)
A publisher of national grid factors for electricity used outside the UK.
- IPCCSixth Assessment Report, Working Group I
The newer GWP values, used by DESNZ only where AR5 values do not exist.
- The National ArchivesOpen Government Licence v3.0
The licence the factors are published under.
- FCAPS26/19: Aligning listed issuers' sustainability disclosures with international standards, ¶¶3.6, 3.12
UK SRS on a comply-or-explain basis for UKLR 6, 14, 15, 16 and 22, periods from 1 January 2027.
- Cabinet OfficePPN 006: Taking account of Carbon Reduction Plans in the procurement of major government contracts
The £5m-a-year contract threshold and the carbon reduction plan condition.
- DESNZ2025 conversion factors methodology paper, Table 9
The 2025 generation factor, 0.17700 kgCO2e/kWh.
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