GHG conversion factors: the UK government set for company reporting

GHG conversion factors are the multipliers that turn what an organisation measures into the greenhouse gas emissions it reports. The UK government conversion factors for company reporting do this for activity data such as the volume of fuel used, the kWh of electricity purchased or the distance travelled, and they keep Scope 1, 2 and 3 separate.

The Department for Energy Security and Net Zero publishes them. Many readers still search for the “Defra conversion factors” or “BEIS conversion factors”, after the departments that held the job before. The GOV.UK collection lists a set for every year from 2002 to 2026.

DESNZ says the factors suit UK organisations of all sizes and international organisations reporting on their UK operations. They are written for the Environmental Reporting Guidelines, including Streamlined Energy and Carbon Reporting. The government adds that they “may also be used for other purposes, but users do so at their own risk”.

They are activity-based. DESNZ points out that they differ from the spend-based multipliers Defra publishes alongside the UK carbon footprint, which are a rougher first estimate for supply chain emissions where activity data is missing. If you use both, say which method covers which line. The wider method is set out in our guide to carbon accounting.

The 2026 conversion factors were published on 11 June 2026. On 31 July 2026 DESNZ republished the flat file to correct values reported as 0 that should have been blank. The full set was not revised.

The headline is electricity. The 2026 methodology paperexplains that the factor used to lag its publication year by two years, because it waited for inventory emissions data. From 2026 it uses Energy Trends statistics and lags by one year. The paper says this produces “a significant drop in the electricity conversion factor between 2026 and 2025”.

The values below are from Table 9 of the methodology paper, which gives factors per kWh including imported electricity. The 2025 set was built on 2023 data; the 2026 set is built on 2025 data. There is no 2024 data year. The calculator above uses the same six figures.

The change reaches everything that runs on electricity. The major changes report records falls of 23% to 26% for electric car factors and a 31% fall for homeworking office equipment, which had not been updated since 2022. It also records large movements in rail, coach and some van and HGV factors, driven by passenger numbers, vehicle registrations and loading rather than the grid.

The rule is in paragraph 1.10 of the 2026 methodology paper, and it is short enough to quote whole.

"The 2026 GHG Conversion Factors are for use with activity data that falls entirely or mostly within 2026. The factors will continue to be improved and updated on an annual basis with the next publication in June 2027."DESNZ, 2026 methodology paper, paragraph 1.10

The factor year follows the activity year. It does not follow the year you publish or file. The 2025 paper carries the same sentence for 2025, so this is settled drafting rather than a one-off. It means a company reporting calendar 2026 in spring 2027 uses a set that was published half-way through the year it describes.

The words “entirely or mostly” do not settle a year split evenly across two calendar years. Pick one approach, apply it every year and state it in your methodology note.

The comparative year, and whether to restate it

SECR asks for the previous year's figures beside the current ones, so the 2026 method change lands in every report that spans it. The paper leaves the decision with the reporter, in paragraph 3.7: “users will need to decide whether they should adjust their previous years' estimates to use the new conversion factors so that they have a consistent time series. This is a recommendation or requirement under some GHG reporting standards”.

If you do not restate, paragraph 3.8 asks you to be open about the gap: the new method “will result in a ‘skipping’ of the 2024 data on UK electricity emissions intensity. This is because the 2025 publication used 2023 data, and the 2026 publication uses 2025 data.” If you do restate, paragraph 3.22 points to Appendix 2, a full time series recalculated on the current method, provided “for users seeking a fully consistent data time series, e.g. those who are retrospectively updating their previous years' emissions estimates.”

Each worksheet in the full set sits in a scope. The methodology paper says fuel factors are for fuel burned at sites or in assets you own or control, UK electricity is for electricity used at your sites and is Scope 2, and transmission and distribution losses and well-to-tank factors are Scope 3. Our overview of Scope 1, 2 and 3 emissions covers the boundaries.

SECR.Large unquoted companies must report emissions from gas, transport fuel and “the purchase of electricity by the company for its own use” under Part 7A of Schedule 7 to SI 2008/410. Quoted companies report on the wider list in Part 7. The factors are the standard way to convert those figures. The Environmental Reporting Guidelinesstill record the government's preference for dual reporting and encourage the location-based method for anyone choosing one. The mechanics are in our SECR reporting guide.

UK SRS S2. Paragraph 29(a)(ii) of UK SRS S2 requires emissions to be measured under the GHG Protocol Corporate Standard, and paragraph 29(a)(v) requires location-based Scope 2. For UK sites, the DESNZ grid factor is the natural location-based figure. Market-based reporting is permitted, not required; see location-based and market-based Scope 2 and our guide to UK SRS S2.

Scope 3 is where the set runs out fastest. It covers travel, freight, waste, water and some materials. Most purchased goods and services need supplier data or spend-based factors, as our Scope 3 emissions guide explains.

Until 2025 there were three spreadsheets. The 2025 publicationdescribed the condensed set as the version “recommended for most, and new, users”, the full set as for advanced users, and the flat file as a machine-readable copy of the full set.

That has changed. Paragraphs 2.3 and 3.3 of the 2026 methodology paper say the same thing: “Note that as of 2026, the Condensed set is no longer published; however, this table has been retained here so that users can find values from previous publication years.”

What replaces the condensed set

Nothing new replaces it. The full set takes its place, and the 2026 publication page now labels it “Conversion factors 2026: full set (for all users)”, where the 2025 page had pointed most users to the condensed version. The flat file is labelled “for automatic processing only”. For a reader who used to open the condensed set, the full set is the file to use.

Nothing a condensed-set user relied on has gone. Tables 2 and 6 of the methodology paper, kept for this reason, show the Fuels, Fuel properties, Conversions, UK electricity and Transmission and distribution worksheets in both versions. The full set adds the worksheets the condensed set never carried, among them well-to-tank fuels, well-to-tank electricity, and heat and steam.

DESNZ asks new users to read the Introduction worksheet and regular users to read the “What's new” worksheet. Both are in the full set. If a template or tool you use was built on the condensed layout, re-map it to the full set's worksheet names before loading 2026 data.

The GHG Protocol Corporate Standard covers the seven gases of the Kyoto Protocol: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulphur hexafluoride and nitrogen trifluoride. The 2004 text named six; nitrogen trifluoride was added by an amendment in February 2013. Our GHG Protocol guide covers the standard itself.

The UK factors report CO2, CH4 and N2O separately and as a CO2e total. Refrigerants and process gases have their own worksheet, with one factor for Kyoto products only and another including non-Kyoto products.

The methodology paper says AR5 keeps the factors consistent with UNFCCC reporting and the UK inventory, and that newer IPCC methods “have not yet been officially accepted for use under the UNFCCC”. Do not swap in AR6 values for methane and nitrous oxide.

Three mistakes move a SECR figure more than any other. Each is worked below for the same case: a company using 1,000,000 kWh of UK grid electricity in calendar 2026, reporting an intensity ratio per £100,000 of revenue on revenue of £25 million. The correct location-based Scope 2 figure is 1,000,000 kWh × 0.13096 = 130.96 tCO2e, or 0.524 tCO2e per £100,000.

1. Using the “consumed” factor as Scope 2

The consumed factor, 0.14396, is generation plus grid losses. Used as Scope 2 it gives 143.96 tCO2e, 13.00 tonnes or 9.9% too high, and an intensity ratio of 0.576 instead of 0.524. If the company also reports transmission and distribution losses in Scope 3 (12.99 tCO2e at 0.01299), those tonnes are now counted twice. Paragraph 3.9 of the methodology paper classes generation as Scope 2 and losses separately as Scope 3, and the full set keeps them on separate worksheets. One later sentence, in paragraph 3.21, calls the consumed figure the one “typically reported under Scope 2”; we follow paragraph 3.9 and the GHG Protocol split.

2. Using the wrong year's set

Apply the 2025 factor, 0.17700, to 2026 activity and Scope 2 becomes 177.00 tCO2e: 46.04 tonnes, or 35.2%, too high, with an intensity ratio of 0.708. Apply the 2026 factor to 2025 activity and the error runs the other way: 26.0% too low. Both happen when a tool picks the latest set on the day it runs, or when a report filed in 2027 reaches for “this year's” factors.

3. Reporting the factor change as a reduction

Use the same 1,000,000 kWh in both years. The 2025 comparative is 177.00 tCO2e and the 2026 figure 130.96 tCO2e, so the report shows a 26% fall in Scope 2 and in the intensity ratio (0.708 to 0.524) with no change in use. About 6 to 7 of those percentage points are method, not grid. State the change, or restate 2025 on the new basis, before any sentence about progress.

The live intensity figure published half-hourly by NESO's Carbon Intensity service is useful for shifting load, but it is an operational forecast for Great Britain. It is not the annual factor that reporting frameworks expect.

The same factor set lands differently depending on why you are using it. Pick the description that fits; each tab says what applies, what to do next and by when.

The timeline marks what has passed and what comes next as of the day you read it. The 2027 set is due in June 2027, but DESNZ has not given a day, so it is not plotted.

Conversion factorDESNZ

A multiplier that turns activity data into kilograms of CO2e.

Activity data¶1.10

What you measure: kWh, litres, kilometres, tonnes. The year it falls in decides the factor set.

CO2eGWP

Carbon dioxide equivalent: CO2, CH4 and N2O combined using global warming potentials.

Global warming potential (GWP)AR5

The weighting for each gas; the 2026 set uses CH4 = 28 and N2O = 265.

Electricity generatedScope 2

The UK electricity factor for power supplied to the grid, including imports.

Transmission and distribution lossesScope 3

Electricity lost on the grid before it reaches you, with its own factor.

Electricity consumedboth

Generation plus losses in one factor. Not a Scope 2 figure on its own.

Data year¶3.8

The year of grid data behind a set: 2023 for the 2025 set, 2025 for the 2026 set.

Well-to-tank (WTT)Scope 3

Upstream emissions from extracting, refining and transporting a fuel before use.

Full set2026

Every factor for the year, with worksheet guidance. Labelled for all users.

Flat file2026

The same data in one table, for automatic processing only.

Condensed setto 2025

A shorter spreadsheet for most users. Not published for 2026.