GHG conversion factors 2026: the −26% electricity story
DESNZ published the 2026 UK GHG conversion factors on 11 June 2026, and the headline is a roughly 26% fall in the electricity factor — mostly a methodology change, not a one-year miracle of decarbonisation.
This page explains what changed, which year-set to use, how to apply the factors correctly, and the SECR comparability caveat the change creates.
The 2026 update: why the electricity factor fell ~26%
DESNZ published the 2026 GHG conversion factors on 11 June 2026[1].
The headline change is the UK electricity factor, which fell by roughly 26% compared with 2025[3].
Part of that fall is continued grid decarbonisation, but the larger driver is a new methodology: DESNZ now uses more recent generation data, cutting the reporting lag from around two years to around one[3].
The change affects the UK electricity factor, transmission and distribution losses, and derived factors including rail, EVs and homeworking[3].
Critically, previously published factors are not restated[3].
A company comparing its 2026 electricity emissions against 2025 using the two published factor sets will see a fall that is partly the methodology change, not solely reduced consumption or a genuinely cleaner grid in a single year.
What the UK conversion factors are
The UK greenhouse gas conversion factors for company reporting are a single, free dataset published every year by the Greenhouse Gas Inventory team in the Department for Energy Security and Net Zero[2].
They were historically published under DEFRA, but DESNZ now produces them.
Their job is narrow and important: turn an organisation’s activity data into tonnes of carbon dioxide equivalent so it can report under Streamlined Energy and Carbon Reporting and other frameworks[5].
The factors are built primarily on the National Atmospheric Emissions Inventory, compiled to the IPCC 2006 Guidelines, and serve UK organisations of all sizes as well as international organisations reporting UK operations[5].
Which year’s factors to use
The single most common error is using the wrong year-set.
The rule is simple: use the factors for the year your reporting period falls in, not the year you compile or submit the report[2].
If your reporting year is 2026, you use the 2026 conversion factors — even if you are pulling the report together in 2027.
A new set is published annually, so each reporting year has its own matching factors[2].
DESNZ keeps every year-set in a single collection, so older sets remain available alongside the latest one.
That is deliberate: it lets you report a prior year correctly rather than forcing the newest figures onto it[2].
| Reporting period | When you report | Factor set to use |
|---|---|---|
| 2025 reporting year | Compiled in 2026 | 2025 conversion factors |
| 2026 reporting year | Compiled in 2027 | 2026 conversion factors (published 11 Jun 2026) |
| 2027 reporting year | Compiled in 2028 | 2027 conversion factors (once published) |
When a single report spans more than one year — for example, a trend comparison — each year is converted using its own set.
Mixing sets within one calculation distorts the comparison you are trying to make, and for electricity specifically, the 2026 methodology change makes that distortion larger than usual[2][3].
How a conversion factor is applied
Every emissions calculation reduces to the same arithmetic: activity data multiplied by the matching conversion factor gives tonnes of CO2 equivalent[1].
Activity data is whatever you can measure from invoices and records — kilowatt-hours of electricity, cubic metres or kilowatt-hours of gas, litres of fuel, or kilometres travelled.
The factor translates each unit into emissions[5].
The discipline is in the matching.
The factor must align with the activity on four fronts at once: the right fuel or activity, the right unit, the right energy basis, and the right reporting year.
| Activity data | Conversion factor | Result |
|---|---|---|
| Electricity consumed (kWh) | Grid-average electricity factor (2026: methodology changed) | Scope 2 location-based tCO2e |
| Natural gas (kWh, gross CV) | Natural gas factor | Scope 1 tCO2e |
| Fuel purchased (litres) | Fuel-specific factor | Scope 1 fleet tCO2e |
| Distance travelled (km) | Mode-specific travel factor | Scope 3 business-travel tCO2e |
Location-based versus market-based Scope 2
Purchased electricity is the part of the calculation most often misreported, because there are two legitimate methods and they answer different questions[4].
The location-based method uses the average emissions intensity of the grid where the electricity is consumed.
For UK consumption that is the DESNZ grid-average electricity factor, which reflects the average carbon intensity of the grid mix — and, from 2026, a data lag of around one year rather than two[4][3].
NESO’s live half-hourly grid carbon intensity is a different, faster-moving number and is not a substitute for the annual DESNZ factor in a compliance calculation[8].
The market-based method reflects the electricity a company has contractually chosen.
Its factors come from contractual instruments — renewable supply contracts, REGO-backed tariffs, or the residual mix where no specific contract applies[4].
The GHG Protocol Scope 2 Guidance requires companies that operate in markets offering contractual instruments to report both figures.
This is dual reporting, and it exists so that the two views — grid reality and procurement choice — can be tracked side by side[4].
For the live grid numbers behind the annual factor — and why they are not the same thing — see our UK grid carbon intensity page.
The common mistakes
Most conversion-factor errors are not exotic.
They cluster around a handful of recurring traps, and each has a clear fix.
| Mistake | Why it is wrong | Fix |
|---|---|---|
| Wrong year-set | A fresh set is published each year, so the wrong one misstates emissions | Match the set to the reporting period, not the submission date |
| Treating the 2026 fall as pure decarbonisation | The −26% electricity move is mostly a methodology change, not restated history | Footnote the methodology break in any year-on-year comparison |
| Mixing methods on Scope 2 | Location-based and market-based answer different questions | Report each on its own terms; do not blend them |
| Double counting electricity | Claiming a renewable contract and discounting the grid figure counts it twice | Keep location-based and market-based separate |
| Wrong energy basis | UK gas is billed on gross CV; the net-CV factor gives a different result | Use the gross-CV factor where the bill is on a gross basis |
For the value-chain side of the calculation, the same matching discipline applies but the data is harder to obtain.
See our guide to Scope 3 emissions reporting for how to handle business travel, purchased goods and the rest of the value chain.
How the factors support SECR and UK SRS S2
The conversion factors are not an end in themselves — they are the input that makes carbon reporting frameworks work.
Under SECR, qualifying companies report energy use and the resulting greenhouse gas emissions, and the 2026 DESNZ factors are the standard tool for converting 2026 activity into that report[5][7].
Under UK SRS S2, the UK climate disclosure standard, in-scope companies must report gross Scope 1, Scope 2 and Scope 3 emissions measured in line with the GHG Protocol Corporate Standard[6].
Because the DESNZ factors are a recognised input for the GHG Protocol calculation, the same dataset that has long served SECR also feeds the newer UK SRS S2 reporting — one factor source, two regimes[4].
The 2026 methodology change applies equally to both.
The same factor choice also surfaces in CDP’s questionnaire, where verified Scope 1–2 data using the correct year-set is one of the clearest signals of a credible response — see our CDP scores & scoring methodology page.
For a worked SECR template that cites the 2026 factors, see our SECR reporting template.
Downloading the official dataset
There is one authoritative home for the figures, and it is not a third-party summary: the DESNZ publication on GOV.UK.
The 2026 set is provided as a condensed set for most users, a full set for advanced users, and a flat file for automated processing, alongside the methodology and major-changes papers[1].
New users are pointed to the introductory worksheet in the condensed set; regular users are directed to the 2026 Major Changes report, which sets out the electricity-factor methodology change in full[3].
Every year-set lives in the DESNZ collection, so once the next set is published it appears there alongside the previous ones.
Bookmark the collection rather than a single year’s file[2].
Download the 2026 conversion factors from GOV.UK or browse the full annual collection.
UK emissions factors: frequently asked questions
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 by roughly 26% versus 2025 — partly continued grid decarbonisation, but mostly a new methodology that uses more recent generation data and cuts the reporting lag from two years to one. The change affects UK electricity, transmission & distribution losses, and derived factors such as rail, EVs and homeworking. Previously published factors are not restated, so a straight year-on-year comparison needs a methodology caveat, not just a "the grid got cleaner" read.
Who publishes the UK greenhouse gas conversion factors?
The UK greenhouse gas conversion factors for company reporting are published annually by the Greenhouse Gas Inventory team in the Department for Energy Security and Net Zero (DESNZ). They were historically badged under DEFRA, but DESNZ now produces them. They are a free resource that lets organisations convert activity data into tonnes of carbon dioxide equivalent (tCO2e), and they underpin Streamlined Energy and Carbon Reporting (SECR). The factors are based primarily on the National Atmospheric Emissions Inventory, compiled to the IPCC 2006 Guidelines.
Which year of conversion factors should I use?
Use the conversion factors for the year your reporting period falls in, not the year you happen to be submitting the report. If you are reporting emissions for the 2026 reporting year, use the 2026 conversion factors — even if you are compiling the report in 2027. A new set is published each year, so mixing years within a single report, or defaulting to the latest set because it is the most recent file, is a common source of error.
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 consumed — for UK consumption, the DESNZ grid-average electricity factor. The market-based method reflects the electricity a company has contractually chosen, using emission factors derived from contractual instruments such as renewable supply contracts or REGO-backed tariffs. The GHG Protocol Scope 2 Guidance requires companies with operations in markets that offer contractual instruments to report both figures — known as dual reporting.
Can I compare my 2026 electricity emissions with 2025 using the new factors?
Not directly, without a caveat. Because the 2026 electricity factor reflects a new methodology rather than a restatement of prior years, a fall in your reported tCO2e between 2025 and 2026 partly reflects the factor changing, not only your consumption or the grid genuinely decarbonising by that much. Flag the methodology break wherever you present a year-on-year electricity comparison, and consider footnoting which factor set each year used.
How do the conversion factors relate to SECR and UK SRS?
SECR requires qualifying companies to report energy use and the resulting greenhouse gas emissions, and the DESNZ conversion factors are the standard tool for that conversion. UK SRS S2, the UK climate disclosure standard, requires gross Scope 1, Scope 2 and Scope 3 emissions measured in line with the GHG Protocol Corporate Standard. The DESNZ factors are a recognised input for the GHG Protocol calculation, so the same factor set supports both the existing SECR regime and the emerging UK SRS S2 reporting.
- Greenhouse gas reporting: conversion factors 2026 — GOV.UK / Department for Energy Security and Net Zero · Published 11 June 2026; condensed, full and flat-file sets, plus methodology and major-changes papers
- Government conversion factors for company reporting of greenhouse gas emissions — GOV.UK / DESNZ · Annual collection — each year-set sits here once published
- 2026 Major Changes report and Methodology Paper — GOV.UK / DESNZ · Electricity factor down ~26%; new methodology cuts the data lag from two years to one; affected tabs listed
- GHG Protocol Scope 2 Guidance — Greenhouse Gas Protocol · Defines location-based and market-based methods and the dual-reporting requirement
- Environmental reporting guidelines: including Streamlined Energy and Carbon Reporting requirements — GOV.UK / DESNZ · How the factors are applied under SECR
- A Corporate Accounting and Reporting Standard — Greenhouse Gas Protocol · Defines gross Scope 1, 2 and 3 accounting — the basis UK SRS S2 and SECR both measure against
- The Companies (Directors’ Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018 — legislation.gov.uk · The statutory instrument that created SECR, which the DESNZ factors are used to satisfy
- Carbon intensity of the GB electricity system — NESO · Live half-hourly grid carbon intensity — distinct from, and not a substitute for, the DESNZ annual factor