UK DEFRA Emission Factors (2026)
The UK Government GHG Conversion Factors — published each June by the Department for Energy Security and Net Zero (DESNZ) and the Department for Environment, Food & Rural Affairs (DEFRA) — are the most widely cited pre-aggregated emission factor dataset in corporate carbon accounting worldwide. Despite their UK origin, they serve as the operative methodology for thousands of organisations globally where local factors are unavailable or where a single, traceable, audit-grade dataset is required.
This page is the methodological reference for the dataset. It explains how DEFRA constructs its factors, how they integrate with IPCC and GHG Protocol standards, where the geographic boundaries lie, and how GreenCalculus implements them through the MasterBrain data layer. The full numerical dataset belongs in the DEFRA 2026 emission factor data page; this page is for practitioners who need to understand the methodology behind the numbers before applying them.
Need these factors in your software, or cited for an audit? Those questions have their own pages: How do I get DEFRA conversion factors into my software automatically? · Where do audit-grade emission factors and their citations come from?
1. What DEFRA Emission Factors Are
DEFRA emission factors are not raw scientific measurements. They are pre-aggregated, regulatory-grade conversion factors derived from underlying scientific data and reformatted into a directly usable form for corporate inventory work. Understanding this distinction is essential for using them correctly.
A DEFRA factor takes a physical activity — combusting one litre of diesel, consuming one kWh of electricity, flying one passenger-kilometre, disposing of one tonne of waste — and returns a single CO2-equivalent value. That single number already embeds all relevant greenhouse gases (CO2, CH4, N2O), their respective Global Warming Potentials, and where applicable, lifecycle and load-factor adjustments. The conversion is complete; no further GWP application is required, and no further multi-gas calculation is necessary. For most corporate inventory applications, the formula is therefore straightforward:
1.1 How a DEFRA Factor Is Built
Take natural gas combustion as the canonical example. When natural gas is burned, three greenhouse gases are produced: CO2 from the carbon content of the fuel; CH4 (primarily methane slip — uncombusted methane that passes through the burner); and N2O from high-temperature combustion. Each gas is produced in a known mass per unit of fuel consumed. Each mass is then multiplied by its IPCC AR5 100-year GWP — CO2 × 1, CH4 × 28, N2O × 265 — and the three CO2-equivalent contributions are summed into the single factor printed in the DEFRA workbook.
Because DEFRA factors are pre-aggregated CO2e values, the CH4 and N2O components are already inside the factor at the appropriate AR5 GWP. Multiplying a DEFRA CO2e factor by a GWP value applies GWP twice. The result will overstate emissions materially. The factor for natural gas (0.18231 kg CO2e/kWh) already includes methane slip and combustion N2O at AR5 GWP. Do not multiply on top. Reference: methane in inventory work.
Provider directory
Need help keeping this up all year?
See who does this work. Every listing names the standards it works to, and paid placements are labelled. Including The Carbon Trust and KERAMIDA.
Browse 6 carbon accounting & inventory providers →Do this work? A listing is US$390 a year. Get listed →
2. How DEFRA Fits Into the Standards Stack
DEFRA emission factors do not exist in isolation. They sit between scientific source data and corporate accounting methodology, in the middle of a three-layer architecture. Understanding each layer clarifies why DEFRA is trusted, how it is validated, and where its limitations begin.
When a verifier asks “where does this emission factor come from?”, a defensible answer for a DEFRA-based natural gas calculation reads: “DEFRA 2026 conversion factor for natural gas, 0.18231 kg CO2e/kWh GCV, sourced from UK Government GHG Conversion Factors 2026 published by DESNZ in June 2026 (Fuels tab, cell D42). GWP values embedded in the factor are IPCC AR5 GWP-100, per the DEFRA workbook Introduction tab Row 35. Applied under the GHG Protocol Corporate Standard scope classification for stationary combustion.” That three-layer citation is what makes the inventory entry audit-ready.
DEFRA 2026 explicitly uses IPCC AR5 (2013) GWP values, not AR6 (2021). This is documented on the workbook Introduction tab, Row 35: “The GWPs used in the calculation of CO2e are based on the IPCC Fifth Assessment Report (AR5) over a 100-year period.” Several major reporting frameworks (Paris Agreement / UNFCCC) similarly require AR5 through transition periods. The GHG Protocol Corporate Standard recommends AR6 for new inventories, which creates a methodological tension when DEFRA factors are used inside GHG Protocol inventories. GreenCalculus addresses this with two calculation modes (Section 8.1): regulatory mode reads DEFRA factors at AR5 directly; engineering mode reads gas-by-gas component masses and applies AR6 GWP separately.
3. Well-to-Tank vs Tank-to-Wheel — The Scope 1 / Scope 3 Split
This is the most consistently mishandled feature of DEFRA factors in corporate inventories and a frequent finding in third-party verification. For most fuels, DEFRA publishes two distinct factors: one for combustion at the point of use (Scope 1), and one for the upstream supply chain that delivers the fuel (Scope 3 Category 3).
Emissions from the actual combustion of the fuel at the point of use — the chemistry of diesel burning in an engine, gas burning in a boiler, jet fuel burning in a turbine. These are direct emissions from owned or operationally controlled sources. The headline DEFRA combustion factors (e.g. diesel 2.58354 kg CO2e/litre) are TTW values.
Emissions from extracting, refining, processing, and transporting the fuel to the point at which it is consumed. These are upstream supply-chain emissions and fall under Scope 3 Category 3 (fuel- and energy-related activities) under the GHG Protocol. DEFRA publishes a separate WTT factor for each major fuel type on the “WTT- fuels” workbook tab.
The two components belong in different places: the TTW figure within Scope 1 and the WTT figure within Scope 3 Category 3. Under the GHG Protocol Corporate Standard, Scope 3 reporting is optional. Under the GHG Protocol Scope 3 Standard, which a company follows once it reports Scope 3, Category 3 must be accounted for or its exclusion disclosed and justified. Frameworks that require significant Scope 3 categories, such as CSRD ESRS E1 and the CDP questionnaire, therefore bring the WTT entry in even when it looks proportionally small. For organisations with significant fossil fuel consumption, omitting Scope 3 Category 3 is one of the most material disclosure gaps that surfaces during ISO 14064-3 verification.
For organisations seeking a single “well-to-wheel” total without scope disaggregation, DEFRA publishes combined WTT+TTW factors on the relevant tabs. These are useful for quick estimates and high-level disclosure but cannot be used where reporting requires Scope 1 and Scope 3 to be disclosed separately — which they do under the GHG Protocol, CDP, GRI 305, ISO 14064-1, and CSRD ESRS E1. For compliant disclosure, always use the disaggregated TTW and WTT factors.
4. What DEFRA 2026 Covers — Category by Category
DEFRA 2026 covers seven principal activity categories. The tables below map each category to its GHG Protocol scope and present the headline factors as implemented in MasterBrain v2026.7. All values are reconciled against the DEFRA 2026 source workbook on a per-cell basis with full audit traceability.
4.1 Stationary Combustion — Fuels (Scope 1)
| Fuel | DEFRA 2026 factor | Unit | Notes |
|---|---|---|---|
| Natural gas (energy basis) | 0.18231 | kg CO2e / kWh (GCV) | UK gas billing standard. Includes combustion CH4 and N2O at AR5 GWP. |
| Natural gas (volume basis) | 2.02633 | kg CO2e / m3 | Volume at 15°C, 1 atm. Use for industrial volume meters. |
| Natural gas (100% mineral, no biomethane) | 2.04987 | kg CO2e / m3 | Pure fossil supply. Use only when biomethane content is confirmed zero. |
| Diesel (average biofuel blend, B7) | 2.58354 | kg CO2e / litre | UK pump diesel. Default for road and most stationary diesel. |
| Diesel (100% mineral, unblended) | 2.66155 | kg CO2e / litre | Pure fossil. Use only when supply is confirmed unblended. |
| Gas oil (red diesel / rebated) | 2.75541 | kg CO2e / litre | Pure fossil distillate. Generators, agricultural equipment, diesel rail traction. |
| Diesel HVO (hydrotreated vegetable oil) | 0.03558 | kg CO2e / litre | Renewable diesel. Scope 1 = trace CH4+N2O only. Biogenic CO2 (2.43 kg/L) reported separately, out of scope. |
| Petrol (average biofuel blend) | 2.07500 | kg CO2e / litre | UK pump petrol, average biofuel blend (E10 has been the standard UK grade since September 2021). |
| Petrol (100% mineral) | 2.35372 | kg CO2e / litre | Pure fossil petrol. Use only when supply is confirmed unblended. |
| LPG | 1.55713 | kg CO2e / litre | Standard UK LPG blend (autogas). |
| Fuel oil (heavy residual) | 3.17492 | kg CO2e / litre | Heavy residual oil for industrial steam and process heat. |
| Marine fuel oil (MFO / HFO bunker) | 3.10202 | kg CO2e / litre | Residual marine bunker fuel. |
| Coal — industrial / steam | 2415.04 | kg CO2e / tonne | Industrial steam, process heat. |
| Coking coal | 3164.65 | kg CO2e / tonne | Metallurgical use. |
| Biogas | 0.00022 | kg CO2e / kWh | Biogenic. Scope 1 CO2e is trace (CH4+N2O only). Biogenic CO2 reported separately, out of scope. |
| Biomass (wood pellets) | 57.25 | kg CO2e / tonne | Biogenic CO2 excluded from Scope 1 total per GHG Protocol; mandatory disclosure as supplementary memo item. |
Precision note. DEFRA publishes factors to five-decimal precision in the source workbook. Earlier prevalent rounded values (diesel 2.68, petrol 2.31, natural gas 2.04) are approximations from secondary publications and do not reproduce DEFRA’s exact reconciliation against fuel composition data. The MasterBrain v2026.7 reconciliation aligned all fuel factors to the source workbook directly. Use the precise values for any audit-grade disclosure.
4.2 Grid Electricity — UK (Scope 2)
| Grid | DEFRA 2026 | DEFRA 2025 | Change | Note |
|---|---|---|---|---|
| United Kingdom | 0.13096 | 0.17700 | −26% | Location-based, generation only (T&D losses are a separate factor). Covers Northern Ireland as well as Great Britain. Now built on 2025 data. |
The 26% reduction in the UK grid factor between DEFRA 2025 and 2026 is the most material single change in the 2026 release for organisations with significant UK Scope 2 consumption. It is part cleaner grid and part change of method. DEFRA’s 2026 major-changes report says the data used to lag the publication year by two years, and the lag is now one year, using the latest Energy Trends statistics. The 2025 release used 2023 data and the 2026 release uses 2025 data, so the step covers two years of grid change. DEFRA attributes about 16 percentage points of the fall to 2023–2024 grid changes, about 3 points to 2024–2025, and the remaining 6–7 points to methodological changes and corrections. Switching from DEFRA 2025 to 2026 therefore lowers reported Scope 2 with no change in operations, and the switch should be disclosed under the GHG Protocol consistency principle. Where the change is material to the inventory, base-year recalculation should be considered. See the GHG Protocol recalculation policy.
DEFRA 2026 publishes a location-based UK grid factor only, and no overseas grid factors. Its own Overseas electricity tab says: “We no longer provide overseas CO2 emission factors. They are available for sale from the International Energy Agency (IEA) website.” Market-based Scope 2 reporting — required when Renewable Energy Certificates, REGOs, Power Purchase Agreements, or Guarantees of Origin are held — requires supplier-specific or instrument-specific factors that DEFRA does not provide. Both methods must be reported in parallel where contractual instruments exist. See Market vs Location Methods and the Scope 2 dual reporting requirement.
4.3 Company Vehicles — Mobile Combustion (Scope 1 / Scope 2)
| Vehicle | DEFRA 2026 | Unit | Scope | Change vs DEFRA 2025 |
|---|---|---|---|---|
| Car — small, petrol | 0.14257 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Car — medium, petrol | 0.17411 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Car — medium, diesel | 0.17209 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Car — medium, hybrid | 0.11678 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Car — average, petrol | 0.16152 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Car — average, battery electric (charging electricity) | 0.02686 | kg CO2e / km | S2 | −23% to −26% Cleaner grid and more efficient cars (all car BEV/PHEV electricity rows) |
| Car — average, plug-in hybrid | 0.08959 + 0.00873 | kg CO2e / km | S1 + S2 | Fuel part (Passenger vehicles tab) plus charging electricity (UK electricity for EVs tab) |
| Van — average (up to 3.5 t), diesel | 0.25716 | kg CO2e / km | S1 | Below DEFRA’s 5% reporting threshold |
| Van — average (up to 3.5 t), battery electric (charging electricity) | 0.04260 | kg CO2e / km | S2 | −22% to −35% Range across van BEV rows |
| HGV — articulated, all (average laden), diesel | 0.93374 | kg CO2e / km | S1 | Not listed as a major change |
Changes are from DEFRA’s 2026 major-changes report, which lists only moves above 5% for Scope 1 and 2 sources and above 10% for Scope 3. “Below threshold” means DEFRA did not list the row. Electric rows exclude the separate T&D-for-EVs factor.
Scope classification note. For company-owned or leased vehicles, the electricity used to charge a battery electric vehicle is reported in Scope 2 (purchased electricity), not Scope 1, because the emissions arise where the electricity is generated. PHEV emissions split between Scope 1 (the fuel burned) and Scope 2 (the charging electricity). DEFRA’s charging factors assume the UK grid; for vehicles charged elsewhere, multiply the vehicle’s kWh per km by that country’s location-based grid factor (for US sites, the EPA eGRID subregion factor).
4.4 Business Travel — Aviation and Rail (Scope 3 Category 6)
| Travel type | DEFRA 2026 | Unit | Change vs DEFRA 2025 |
|---|---|---|---|
| Flight — domestic, average passenger (with RF) | 0.22928 | kg CO2e / passenger-km | Unchanged |
| Flight — short-haul, economy (with RF) | 0.12576 | kg CO2e / passenger-km | Unchanged |
| Flight — short-haul, business (with RF) | 0.18863 | kg CO2e / passenger-km | Unchanged |
| Flight — long-haul, economy (with RF) | 0.11704 | kg CO2e / passenger-km | Unchanged |
| Flight — long-haul, premium economy (with RF) | 0.18726 | kg CO2e / passenger-km | Unchanged |
| Flight — long-haul, business (with RF) | 0.33940 | kg CO2e / passenger-km | Unchanged |
| Flight — long-haul, first (with RF) | 0.46814 | kg CO2e / passenger-km | Unchanged |
| Rail — national rail | 0.03092 | kg CO2e / passenger-km | −13% from 0.03546 |
| Rail — international rail | 0.01135 | kg CO2e / passenger-km | +154% to +156% from 0.00446 |
| Light rail and tram | 0.02121 | kg CO2e / passenger-km | −26% from 0.02860 |
| London Underground | 0.01549 | kg CO2e / passenger-km | −44% to −45% from 0.02780 |
| Coach | 0.03948 | kg CO2e / passenger-km | +42% to +43% from 0.02776 |
Rail and coach values are from the DEFRA 2026 and 2025 workbooks, Business travel- land tab. Flight values are live from MasterBrain; DEFRA 2025 and 2026 publish identical air factors.
DEFRA’s 2026 major-changes report lists business-travel air as “No major changes this year”, and every passenger air factor is identical to DEFRA 2025. The large aviation movement was in the 2025 release (−16% to −42%), when DEFRA replaced COVID-affected 2021 load factors. Rail is where 2026 moved: DEFRA rebuilt national rail, international rail, light rail and the London Underground on post-pandemic passenger-km and fleet data, which had last been estimated from pre-COVID figures. An inventory that carried the 2025 rail factors into 2026 overstates national rail by about 15% and understates international rail by more than half. DEFRA shows each flight factor with and without radiative forcing (RF); report which one you used.
4.5 Freight — Goods Transport (Scope 3 Categories 4 & 9)
| Freight mode | DEFRA 2026 | Unit | Note |
|---|---|---|---|
| Road — HGV, all diesel, average non-refrigerated (average laden) | 0.10356 | kg CO2e / tonne-km | Not listed as a major change |
| Road — HGV articulated, average non-refrigerated (average laden) | 0.07926 | kg CO2e / tonne-km | Not listed as a major change |
| Road — HGV rigid >17 t (average laden) | 0.17256 | kg CO2e / tonne-km | Average laden |
| Road — HGV rigid 7.5–17 t (average laden) | 0.43002 | kg CO2e / tonne-km | +18% Lower average loading |
| Road — van, average (up to 3.5 t), diesel | 0.63511 | kg CO2e / tonne-km | Not listed as a major change |
| Rail — freight train | 0.02583 | kg CO2e / tonne-km | Not listed as a major change |
| Sea — container ship, average | 0.01612 | kg CO2e / tonne-km | Not listed as a major change |
| Sea — bulk carrier, average | 0.00353 | kg CO2e / tonne-km | Not listed as a major change |
| Air — long-haul freight flight, to/from UK (with RF) | 0.89939 | kg CO2e / tonne-km | Without RF: 0.53130 |
| Air — short-haul freight flight, to/from UK (with RF) | 1.27835 | kg CO2e / tonne-km | Without RF: 0.75539 |
All values from the DEFRA 2026 workbook, Freighting goods tab. Per-tonne-km factors apply when you know the mass shipped and the distance; when you hire a whole vehicle, use the per-km factor instead. HGV per-km factors for company-owned trucks are in Section 4.3.
4.6 Waste Disposal (Scope 3 Category 5)
Read the attribution rule before using these factors. DEFRA waste-disposal factors follow a specific GHG Protocol convention. Landfill factors are gate-to-grave — collection, transport and in-situ decomposition. Combustion (energy-from-waste), recycling, composting and anaerobic digestion factors cover only transport to the facility: the downstream emissions (and any energy/material recovery) are attributed to the user of the recovered output, not the waste producer. That is why every recovery route below carries the same small transport factor (~4.65 kg CO2e/tonne to a reprocessing/EfW facility, ~9.01 to a composting/AD site). DEFRA’s “Major changes 2026” lists waste disposal as no major changes this year; the figures below are the DEFRA 2026 published values held in MasterBrain (canonical waste_disposal.gbr.*).
| Waste / route | DEFRA 2026 | Unit | Basis |
|---|---|---|---|
| Landfill — mixed municipal (household residual) | 497.29 | kg CO2e / tonne | Gate-to-grave |
| Landfill — food waste | 700.33 | kg CO2e / tonne | Gate-to-grave |
| Landfill — paper / card | 1,164.51 | kg CO2e / tonne | Gate-to-grave |
| Combustion / EfW — mixed | 4.65 | kg CO2e / tonne | Transport to facility only |
| Recycling — paper / card (closed-loop) | 4.65 | kg CO2e / tonne | Transport to facility only |
| Recycling — mixed plastic (closed-loop) | 4.65 | kg CO2e / tonne | Transport to facility only |
| Recycling — glass (closed-loop) | 4.65 | kg CO2e / tonne | Transport to facility only |
| Recycling — metal cans (closed-loop) | 4.65 | kg CO2e / tonne | Transport to facility only |
| Composting (food / garden) | 9.01 | kg CO2e / tonne | Transport to facility only |
| Anaerobic digestion | 9.01 | kg CO2e / tonne | Transport to facility only |
Earlier editions of this page listed gross recovery figures (incineration 15.5, recycling 8–36, composting 116 kg CO2e/tonne). DEFRA’s current factors are transport-only for those routes, per the GHG Protocol attribution above. If you are migrating a multi-year waste inventory, treat this as a methodology restatement — not an operational reduction — and disclose it.
4.7 Water Supply and Treatment (Scope 3)
| Category | DEFRA 2026 | DEFRA 2025 | Note |
|---|---|---|---|
| Mains water supply (UK) | 0.1913 | 0.1913 | Unchanged. The big move was in DEFRA 2025 (+25%), which DEFRA put down to new water-company data with “considerable interannual variation”. |
| Wastewater treatment (UK) | 0.17088 | 0.17088 | Unchanged. An earlier version of this page showed 0.272, which matches no DEFRA edition; corrected. |
Units: kg CO2e per cubic metre. Sources: DEFRA 2026 and 2025 workbooks, Water supply and Water treatment tabs.
4.8 Refrigerant Fugitives (Scope 1)
A refrigerant’s emission factor is its GWP: multiply the mass leaked (kg) by the GWP to get kg CO2e. DEFRA 2026 uses AR5 GWP-100 values on its Refrigerant & other tab, consistent with the rest of the workbook. If your inventory reports on AR6, the values differ, sometimes by more than 15%, so state which set you used. MasterBrain holds the AR6 set used by our refrigerant calculator; both are shown below.
| Refrigerant | DEFRA 2026 (AR5) | IPCC AR6 | Typical use |
|---|---|---|---|
| HFC-134a (R-134a) | 1300 | 1530 | Mobile AC, light commercial refrigeration |
| HFC-32 (R-32) | 677 | 771 | Lower-GWP AC refrigerant |
| R-410A | 1924 | 2256 | Building AC systems |
| R-404A | 3943 | 4728 | Supermarket refrigeration (being phased out) |
| R-507A | 3985 | 4775 | Commercial refrigeration |
| R-1234yf (HFO) | 1 | 0.501 | Newer automotive AC |
Units: kg CO2e per kg leaked. DEFRA column from the DEFRA 2026 workbook, Refrigerant & other tab (Kyoto products). AR6 column is live from MasterBrain (IPCC AR6 WG1 Table 7.SM.7, with blends computed from their components).
5. GWP Is Already Embedded in Every DEFRA Factor
This is the most important technical fact for any practitioner combining DEFRA factors with GHG Protocol methodology. Every DEFRA CO2e factor has GWP applied internally. The conversion from individual gas masses to CO2-equivalent has already been completed before the value reaches the user.
This produces three operational rules that govern every DEFRA-based calculation:
For the underlying GWP science — and for situations where calculations are built from first principles rather than pre-aggregated factors — see the IPCC AR6 standards reference and the complete AR6 GWP dataset. For a glossary-level introduction to the underlying concept, see Global Warming Potential.
6. Geographic Limitations — When DEFRA Applies Outside the UK
DEFRA emission factors reflect UK-specific conditions: UK fuel composition, the UK national grid mix, UK fleet efficiency averages, UK aviation network characteristics, UK waste treatment infrastructure, and UK water utility operations. When applied outside the UK, this introduces varying degrees of inaccuracy depending on the activity category.
| Category | Applicability outside the UK | Risk | Recommended alternative |
|---|---|---|---|
| Fuel combustion (diesel, gas, petrol, LPG, fuel oil) | Broadly applicable — combustion chemistry is universal; UK fuel composition close to OECD averages. | Low | DEFRA acceptable. Local factors preferred where available. |
| Grid electricity | UK-specific. The UK factor reflects the UK generation mix only, and DEFRA no longer publishes overseas grid factors. | High | Use the national publisher’s location-based factor: EPA eGRID subregions for the US, the EEA for EU countries, SEAI for Ireland, RTE for France, NGA factors for Australia, the EMA grid emission factor for Singapore. DEFRA’s Overseas electricity tab names several of these. Lifecycle intensities (for example Ember’s) are not Scope 2 factors. |
| Aviation (business travel) | Broadly applicable — commercial aviation load factors and aircraft types are global. | Low | DEFRA is a common default outside the UK. Its “International, to/from non-UK” rows exist for flights that do not touch the UK. State whether RF is included. |
| Ground transport — ICE | Moderate — vehicle fleet efficiency reflects UK averages; engine technology is global. | Medium | DEFRA acceptable as proxy. Local fleet data preferred where available. |
| Ground transport — BEV / PHEV | UK-specific — BEV and electric component of PHEV emissions reflect the UK grid intensity. | High | Multiply the vehicle’s kWh per km by the local location-based grid factor. |
| Waste disposal | UK-specific — landfill, incineration, and recycling infrastructure varies materially by country. | High | Use national waste treatment factors where available; DEFRA as last-resort proxy with disclosure. |
| Water supply / treatment | UK-specific — reflects UK water company energy intensity. | High | Use local utility data or IPCC defaults. |
| Refrigerants | Universal — refrigerant GWPs are physical constants from IPCC. | Low | DEFRA / IPCC values apply globally without geographic adjustment. |
For organisations headquartered in Singapore or operating across Asia-Pacific, DEFRA is a workable basis for Scope 3 business travel (use the “International, to/from non-UK” air rows) and for most fuel combustion. For Scope 2 electricity, substitute the national publisher’s grid factor, such as Singapore’s EMA grid emission factor or Australia’s National Greenhouse Accounts factors, not the UK value and not a lifecycle intensity. For local waste and water, use Singapore NEA and PUB published factors where available. DEFRA, national and EPA factors can coexist in one inventory; the GHG Protocol asks you to disclose the source used for each category, not to use a single source throughout.
7. Annual Update Cycle — What Changed in DEFRA 2026
DEFRA publishes updated factors each June. The 2026 release (published 11 June 2026) was a quieter year than 2025: DEFRA’s “Major changes 2026” report lists fuels, water, waste disposal and most of business travel as no major changes this year. The material movements are concentrated in electricity-linked factors — the UK grid and everything that derives from it. The previous (2025) cycle’s changes are summarised at the end of this section for multi-year continuity.
The 2025 release was dominated by the post-COVID aviation correction. From DEFRA’s 2025 major-changes report: UK grid −15% (0.20705 → 0.177), from less gas-fired generation and more net imports; business-travel air −16% to −42%, because the 2023 publication had used COVID-affected 2021 load factors; EV electricity factors −13% to −22%; air freight −18% to −23%; open-loop recycling routes −27% (new assumptions about material recovery facilities); HGV freight per tonne-km roughly +11% to +14% and van petrol freight +22% (lower observed payloads); mains water supply +25%. Any inventory spanning the 2024–2025 boundary should disclose the aviation correction so it is not read as a real reduction in travel emissions.
8. GreenCalculus Implementation
GreenCalculus implements DEFRA 2026 factors across all calculators through the MasterBrain data layer (file: gc-master-brain.php, version 2026.7, updated 2026-06-19). The implementation enforces full provenance discipline — every factor is traceable to a named source document, a workbook tab, and a row reference, with verification status recorded explicitly.
Served live from this edition: UK grid electricity, location-based — 0.13096 kg CO2e/kWh [GreenCalculus grid.gbr.electricity.location_based · DEFRA 2026 'UK electricity'!E25 · v2026.284]. This is the one figure on this page that reads from MasterBrain rather than from the 2026 workbook as published; the worked examples and the 2025-to-2026 comparisons above and below stay fixed to the release they describe.
UK Government GHG Conversion Factors 2026, published by DESNZ and DEFRA, June 2026. Source workbook: ghg-conversion-factors-2026-full-set.xlsx. Available at gov.uk/government/collections/government-conversion-factors-for-company-reporting.
Every factor was reconciled cell-by-cell against the source workbook in the v2026.7 release (June 2026). Each entry carries a source object recording the publication it was read from, the exact worksheet-and-cell reference, and the date it was retrieved; the GWP basis is recorded alongside the value on the row itself. The reconciliation produced precision corrections to several headline values (diesel, petrol, natural gas, coal) and added new keys (gas oil, 100% mineral diesel, propane, butane, CNG, LNG, plus complete WTT coverage).
Calculators read MasterBrain factors at runtime via window.gcMasterBrain.fuels, window.gcMasterBrain.transport, window.gcMasterBrain.business_travel, window.gcMasterBrain.freight, window.gcMasterBrain.waste, window.gcMasterBrain.water. Every calculation emits an audit trail citing factor source, value, unit, and GWP basis alongside activity data and result. See it in the Scope 1 Combustion Calculator.
DEFRA publishes each June. GreenCalculus updates the MasterBrain within 30 days of publication, bumps GC_MB_VERSION and GC_MB_DEFRA_YEAR, and re-reads the “Major Changes” document to flag material changes for this standards page. All calculators automatically read the updated factors on next page load. Changelog entries published per the /changelog/ protocol.
8.1 Regulatory Mode vs Engineering Mode
The MasterBrain stores both pre-aggregated DEFRA factors (regulatory mode) and the underlying gas component masses (engineering mode), allowing GreenCalculus calculators to operate in two distinct methodologies:
| Mode | Reads | GWP basis | Use case |
|---|---|---|---|
| Regulatory | .factor (DEFRA pre-aggregated CO2e value) |
AR5 (inherited from DEFRA) | UK regulatory reporting (SECR, ETS), CDP submissions, CSRD ESRS E1 quantification, ISO 14064-1 aligned with DEFRA primary source. |
| Engineering | .components.{co2,ch4,n2o} masses + gwp.*.ar6_100 separately |
AR6 (applied at calculation time) | Latest-science alignment; GHG Protocol AR6 recommendation; gas-by-gas disaggregation for inventory transparency; sensitivity analysis comparing AR5 vs AR6. |
Both modes are correct disclosures of distinct methodological choices. The calculator UI declares which mode is in use and which GWP basis applies. For natural gas combustion the two modes differ by about 0.01%, because CO2 (GWP 1 under both) is over 99% of the factor; the AR5 to AR6 moves (CH4 28 to 29.8 for fossil methane, N2O 265 to 273) only touch the small CH4 and N2O parts. The gap is material for methane-heavy sources and for refrigerants (Section 4.8).
9. Common Reporting Errors
Factor reference: the per-cubic-metre supply and wastewater treatment values, with the French ADEME equivalents alongside the UK ones, are published with the cell each was read from as water supply and treatment emission factors.
10. Frequently Asked Questions
DEFRA emission factors are pre-aggregated CO2-equivalent conversion factors published annually by the UK Government (DESNZ and DEFRA) for use in corporate greenhouse gas reporting. They convert activity data — litres of fuel, kWh of electricity, passenger-kilometres of travel, tonnes of waste — into kg CO2e by combining CO2, CH4, and N2O contributions at IPCC AR5 GWP-100 values. They are the standard dataset for UK corporate reporting, including SECR, and are a common default elsewhere for categories where UK conditions do not distort the result, such as fuel combustion and air travel. Frameworks such as CDP, ISO 14064-1 and ESRS E1 do not prescribe a factor set; they require you to disclose the one you used.
Selectively. DEFRA fuel combustion factors (diesel, natural gas, petrol, LPG, fuel oil) are broadly applicable globally because combustion chemistry is universal and UK fuel composition aligns closely with OECD averages. DEFRA aviation factors include rows for flights between non-UK airports. DEFRA grid electricity factors should never be used for non-UK electricity; DEFRA itself stopped publishing overseas grid factors and points users to national publishers such as the US EPA (eGRID), the EEA, SEAI and RTE. Waste, water, BEV, and PHEV factors are UK-specific and should be substituted with local data where available. The geographic applicability matrix in Section 6 documents the recommended treatment by category.
Annually, in June. The cycle reflects updates in the UK grid generation mix, vehicle fleet efficiency data, aviation load factors, waste treatment infrastructure assumptions, and ongoing methodology refinements. Some categories are stable year-on-year (fuel combustion factors rarely shift materially); others can vary substantially — the UK grid factor fell 26% between DEFRA 2025 and 2026, and in the prior 2025 release aviation long-haul economy fell 42% on a single methodology correction. GreenCalculus updates the MasterBrain within 30 days of each DEFRA publication.
Tank-to-Wheel (TTW) factors capture emissions from combustion of the fuel at the point of use — what happens when fuel burns in an engine, boiler, or turbine. These are Scope 1 direct emissions. Well-to-Tank (WTT) factors capture upstream emissions from extracting, processing, and transporting the fuel before it reaches the point of consumption — these are Scope 3 Category 3 (fuel- and energy-related activities). DEFRA publishes both separately on the “Fuels” and “WTT- fuels” workbook tabs respectively. Under the GHG Protocol, TTW goes in Scope 1 and WTT in Scope 3 Category 3. Scope 3 is optional under the Corporate Standard, but a company reporting Scope 3 under the Scope 3 Standard must account for Category 3 or disclose why it is excluded.
No. DEFRA 2026 uses IPCC AR5 (2013) GWP-100 values, explicitly stated on the workbook Introduction tab Row 35: “The GWPs used in the calculation of CO2e are based on the IPCC Fifth Assessment Report (AR5) over a 100-year period.” This applies CH4 = 28, N2O = 265, SF6 = 23,500. The AR5 basis aligns with current UK national reporting requirements and the Paris Agreement / UNFCCC AR5 transition convention. The GHG Protocol Corporate Standard recommends AR6 for new inventories, creating a methodological tension: organisations using DEFRA factors inside GHG Protocol inventories inherit AR5 GWP whether they intend to or not. GreenCalculus addresses this with regulatory mode (DEFRA, AR5) and engineering mode (component masses with AR6 applied separately) — see Section 8.1. Note: there has been no GWP-version transition across the DEFRA 2024, 2025 and 2026 editions; all use AR5.
The changes are documented in Section 7. DEFRA 2026 was a quiet year — fuels, water, waste and most of business travel are listed as no major changes. The defining movement is the UK grid factor falling 26% (0.177 → 0.131 kg CO2e/kWh) on continued decarbonisation, which pulls down everything electricity-linked: BEV/PHEV factors fell 12–37% and the WTT-electricity factor fell ~20%. Other real moves: coaches +42% (new operator data) and light rail −26%. Fuel-combustion factors moved only marginally (±0.5–2%). Separately, GreenCalculus corrected a wastewater-treatment value (0.272 → 0.17088) that matched no DEFRA edition. Any 2025 → 2026 transition should disclose the grid change explicitly under the GHG Protocol consistency principle.
Apply DEFRA 2026 factors in a live calculation
The Scope 1 Combustion Calculator implements DEFRA 2026 factors with full provenance and surfaces the GWP basis on every result.
Related GreenCalculus References
Foundational standards: GHG Protocol Corporate Standard · IPCC AR6 · ISO 14064-1 · Scope 3 Standard
Other regional factor sources: US EPA eGRID · EU EEA · Ember Yearly Electricity 2025 (lifecycle intensity, not Scope 2)
Methodology references: Scope 2 Market vs Location · Factor Selection Hierarchy · Data Quality Tiering · Calorific Values (LHV vs HHV)
Glossary: GWP · Methane (CH4) · Well-to-Tank · Biogenic CO2
Apply this standard: Scope 1 Combustion · Scope 2 Electricity · Business Travel (Air) · All calculators