UK Government GHG conversion factors 2026 and 2025: the Defra factors explained

What are the UK Government GHG conversion factors?

The UK Government GHG Conversion Factors for Company Reporting are a free set of emission factors published by the Department for Energy Security and Net Zero (DESNZ). They let organisations turn activity data, such as fuel used, kWh of electricity bought or distance travelled, into greenhouse gas emissions for Scope 1, 2 and 3.

DESNZ says they suit UK-based organisations of all sizes, and international organisations reporting on their UK operations. They are the factors the government's Environmental Reporting Guidelines point to, including for Streamlined Energy and Carbon Reporting (SECR), and the ones PPN 006 requires for Carbon Reduction Plans.

Every factor is expressed in kilograms of carbon dioxide equivalent per unit of activity. CO2e puts different greenhouse gases on one scale using their global warming potential. DESNZ bases these mainly on the IPCC's Fifth Assessment Report (AR5), over a 100-year period.

For many activities the total is also split into the parts from carbon dioxide, methane and nitrous oxide. DESNZ says these gas-by-gas factors can be used if desired. Each split adds up to the total kg CO2e factor shown in the tables below.

Why are they called the Defra conversion factors?

Many people still call them the Defra factors. The Department for Environment, Food and Rural Affairs (Defra) published them with the Department of Energy and Climate Change (DECC) in the early 2010s. The 2012 methodology paper, for example, is titled '2012 Guidelines to Defra / DECC's GHG Conversion Factors for Company Reporting'.

Responsibility later passed to the Department for Business, Energy and Industrial Strategy (BEIS), and DESNZ has published every set since 2023. So a search for the Defra conversion factors for 2025 or 2026 leads to these DESNZ files.

Defra does still publish something related but different: spend-based emissions multipliers, alongside its UK and England carbon footprint statistics. DESNZ says these can give an initial assessment of supply chain emissions from what you spend, where you lack activity data. They are not the company reporting factors.

When is each year's set published?

DESNZ publishes a new set once a year, usually in June, together with a methodology paper and a major changes report.

Which year's factors should I use?

Use the factor set that matches the period your activity data covers, not the year you write the report. DESNZ's guidance says: 'You should use the factors that correlates with the activity data on which you are reporting (for example, factors labelled as 2026 should be used for data from calendar year 2026).'

For a financial year that spans two calendar years, DESNZ allows two approaches. Whichever you choose, state it clearly and apply it consistently.

• Majority approach: use the factors for the calendar year that holds most of your data. DESNZ's own examples: April 2026 to March 2027 uses the 2026 factors, and April 2025 to March 2026 uses the 2025 factors. For a July to June year, DESNZ says to use the newest set available.
• Blended approach: weight the two years' factors by the number of days that fall in each, as long as the split is transparent, auditable and applied consistently.

2026 and 2025 factors: electricity, heat and fuels

The electricity factor is for electricity generated. It does not include transmission and distribution (T&D) losses, which DESNZ publishes as a separate Scope 3 factor. Its major changes report says the T&D factor fell by 30% in 2026.

Not every factor is updated each year. DESNZ focuses its updates on high-emitting sources that change over time, such as electricity, natural gas, diesel and petrol. Heat and steam was held at its 2025 value, and LPG, gas oil and burning oil have been held since the 2021 release, which is why they match.

2026 and 2025 factors: vehicles, travel and freight

RF stands for radiative forcing. The with-RF factors include the extra warming effect of non-CO2 emissions at altitude, which DESNZ adds to the CO2 part of the factor as a 70% uplift. DESNZ says organisations should include these effects when reporting air travel, and should not switch between with-RF and without-RF figures from one year to the next.

National rail fell by 13% because DESNZ updated it with Office of Rail and Road data. The previous figure was last updated in 2021 using 2019 data, from before the pandemic. Aviation factors were held at their 2025 values.

2026 and 2025 factors: refrigerants, waste, hotels and homeworking

A refrigerant factor is the gas's global warming potential, so each kilogram of R410A that leaks counts as 1,924 kg CO2e. DESNZ suggests measuring leaks as the amount topped up during the year. DESNZ has held refrigerant factors constant since the 2023 release, except for one blend, R-511A, which the 2026 set corrected.

Landfill factors cover collection, transport and landfill emissions. For combustion and recycling, the factors cover only transport to the energy recovery or recycling site, in line with the GHG Protocol, which is why they are so low. The 2025 set has no closed-loop factor for commercial and industrial waste; its closed-loop factor for mixed paper and board is 4.68568 kg CO2e per tonne.

The full set also includes water supply and water treatment factors, both Scope 3. DESNZ says to report both parts for water. Both were held at their 2025 values in the 2026 set.

Why did the UK electricity factor fall in 2026?

The 2026 UK electricity factor is 0.13096 kg CO2e per kWh, 26% below the 2025 figure of 0.177. DESNZ puts the fall down to a cleaner grid and a new calculation method.

Until 2025 the factor relied on UK greenhouse gas inventory data, which left a two-year lag: the 2025 factor used 2023 data. From 2026 DESNZ uses Energy Trends statistics on fuel used for power, electricity generated, and imports and exports, cutting the lag to one year. The 2026 factor uses 2025 data, so 2024 is skipped.

• Changes in the grid mix between 2023 and 2024: about 16 percentage points of the fall.
• Changes in the grid mix between 2024 and 2025: about 3 percentage points.
• Method changes, improvements and corrections, including better handling of imports and exports and a fix for a small double count affecting autogenerators: the remaining 6 to 7 percentage points.

The change also lowers other factors that depend on grid electricity, including those for electric vehicles, rail and homeworking.

Flat file vs full set

• Full set (for all users): an Excel workbook with an introduction, a What's new sheet, guidance and a worked example on each worksheet, and every factor. Start here if you calculate by hand.
• Flat file (for automatic processing only): the same factors as one long table, one row per factor, for loading into software or databases.
• Methodology paper: how each factor is derived.
• Major changes report: factors that moved by more than 5% (Scope 1 and 2 sources) or 10% (Scope 3), with the reasons.

The 2025 publication also had a condensed set, an abridged version recommended for most and new users. DESNZ stopped publishing the condensed set from 2026, and the 2026 full set is labelled for all users.

Each flat file row has an ID, the scope, up to four category levels, a column label, the unit, the gas and the factor. Many IDs are the same in both years: UK electricity is 7_400_4000_5_1 in the 2025 and 2026 files. Check the description as well as the ID, because labels change. The 2026 set renamed some HGV categories, and the commercial waste column called 'Incineration with Energy Recovery' in 2025 is 'Combustion' in 2026.

How to use the conversion factors

1. Collect a year of activity data in the units DESNZ uses: kWh for gas and electricity, litres for liquid fuels, km or passenger.km for travel, tonnes for waste and kilograms for refrigerant top-ups.
2. Pick the factor set for that year, using the majority or blended approach for a split year.
3. Find the matching row and use the total kg CO2e factor. For gas, check the unit: DESNZ notes most energy billing is on a gross calorific value basis, which matches the kWh (Gross CV) natural gas factor.
4. Multiply: emissions = activity data × conversion factor. Divide kg by 1,000 for tonnes.
5. Decide whether to include optional Scope 3 items, such as well-to-tank emissions and T&D losses, and apply the choice to every source.
6. State the factor year and approach in your report.

Example: a business that used 50,000 kWh of grid electricity in calendar year 2026 multiplies it by 0.13096, giving 6,548 kg, or 6.55 tCO2e of Scope 2. The same use in 2025 would have been 8,850 kg (8.85 tCO2e) at 0.177. A 40,000 kWh gas bill in 2026 gives 40,000 × 0.18231 = 7,292 kg, or 7.29 tCO2e of Scope 1.

To see which activities fall in which scope, read our guide to Scope 1, 2 and 3 emissions.

Sources

1. DESNZ: Greenhouse gas reporting, conversion factors 2026 (updated 31 July 2026) (checked 10 October 2026)
2. DESNZ: Conversion factors 2026, full set (Introduction, What's new and activity worksheets) (checked 10 October 2026)
3. DESNZ: Conversion factors 2026, flat file (revised July 2026) (checked 10 October 2026)
4. DESNZ: 2026 GHG conversion factors methodology report (PDF) (checked 10 October 2026)
5. DESNZ: 2026 GHG conversion factors major changes report (PDF) (checked 10 October 2026)
6. DESNZ: Greenhouse gas reporting, conversion factors 2025 (checked 10 October 2026)
7. DESNZ: Conversion factors 2025, flat file (checked 10 October 2026)
8. GOV.UK: UK government conversion factors for company reporting of greenhouse gas emissions (collection) (checked 10 October 2026)
9. DESNZ: Greenhouse gas reporting, conversion factors 2023 (change history) (checked 10 October 2026)
10. DESNZ: Greenhouse gas reporting, conversion factors 2024 (change history) (checked 10 October 2026)
11. Defra and DECC: 2012 Guidelines to Defra / DECC's GHG Conversion Factors for Company Reporting, methodology paper (PDF) (checked 10 October 2026)
12. GOV.UK: Environmental reporting guidelines, including Streamlined Energy and Carbon Reporting requirements (checked 10 October 2026)
13. Cabinet Office: PPN 006 technical standard for completion of Carbon Reduction Plans (checked 10 October 2026)