Data · Electricity
UK grid carbon intensity: what the number is, and what it is not
UK grid carbon intensity changes every half hour, and NESO publishes it live through the Carbon Intensity service.
As an annual figure, DESNZ’s Fuel Mix Disclosure data table puts the carbon dioxide intensity of UK generation in 2025 at 147 g/kWh.
Neither is the number a carbon report uses, which is the DESNZ conversion factor: 0.13096 kgCO2e per kWh for activity in 2026.
Half-hourly
The live number: NESO’s carbon intensity
carbonintensity.org.uk is NESO’s service, developed with Environmental Defense Fund Europe, the University of Oxford Department of Computer Science and WWF.
NESO describes it as the world’s first carbon intensity forecast with a regional breakdown, forecasting “the carbon intensity and generation mix 96+ hours ahead”.
The Carbon Intensity API returns half-hour periods, each with a forecast and an actual intensity in grams of CO2 per kWh and an index band such as “low”.
The same data sits on the NESO data portal, and NESO announced its real-time dashboard as a view of Britain’s progress in decarbonising electricity.
It is a Great Britain figure, which is the system NESO operates.
Its uses are operational: deciding when to run flexible load, testing what a time-matched clean-power claim would take, and seeing the grid respond to weather.
Annual
The annual number: DESNZ’s Fuel Mix Disclosure
DESNZ publishes an “estimated carbon dioxide emissions intensity of UK generation” each year in its Fuel Mix Disclosure data table, the table suppliers use under the Electricity (Fuel Mix Disclosure) Regulations 2005.
For 2025 the overall average is 147 g/kWh, with natural gas generation at 365 g/kWh and nuclear and renewables at zero.
The table for the previous disclosure period, 2023/24, gave 171 g/kWh for 2023.
Both figures cover only emissions from UK generators in the operational phase, excluding the fuel supply chain, maintenance and electricity imports.
DESNZ says they align with table 5.14 of the Digest of UK Energy Statistics, which is where the longer series lives; later editions can revise earlier years.
The same 2025/26 table gives a UK fuel mix of 48.0% renewables, 31.4% natural gas, 13.7% nuclear, 4.7% coal and 2.2% other, on an attribute basis that includes an allocation for imports.
DESNZ notes that no electricity was generated from coal in the UK in 2025, so the 2024 coal intensity is used for Fuel Mix calculations.
| Year | UK generation, g/kWh CO2 | Table |
|---|---|---|
| 2025 | 147 | Fuel Mix Disclosure 2025/26 |
| 2023 | 171 | Fuel Mix Disclosure 2023/24 |
The reporting connection
Grid intensity is not your Scope 2 factor
Three numbers describe UK electricity, and each answers a different question.
| NESO live intensity | DESNZ Fuel Mix Disclosure | DESNZ conversion factor | |
|---|---|---|---|
| Example | Half-hourly forecast and actual | 147 g/kWh (2025) | 0.13096 kgCO2e/kWh (2026 set) |
| Gases | CO2 | CO2 | CO2e (CO2, CH4, N2O) |
| Imports | — | Excluded | Included |
| Area | Great Britain, and regions | UK generators | UK grid |
| Built for | Operations and forecasting | Supplier fuel mix disclosure | Company reporting, incl. SECR |
| Use in a carbon report | Context only | Context only | Location-based Scope 2 |
The number a carbon report uses is the DESNZ electricity conversion factor for the matching year: 0.13096 kgCO2e per kWh in the 2026 set, for activity mostly in 2026.
It is built from 2025 data, includes the proportion of imported electricity and is expressed in CO2 equivalent, which is why it does not match the 147 g/kWh CO2-only figure for the same data year.
Under SECR (SI 2018/1155) it is the standard tool for converting purchased electricity, and under UK SRS S2 it supplies the location-based figure the standard requires.
UK SRS S2 names no factor set; ¶B29 asks for factors that best represent the entity’s activity and for disclosure of which were used.
Choosing and applying the right year’s factor is covered on our page on the UK emissions factors, and the 2025 set is on the 2025 conversion factors.
Why the factor lags
From a two-year lag to one
The 2026 methodology paper, ¶3.5, says the old method left “a two-year time lag between when emissions occurred and when the conversion factor is published”.
From 2026 the factor uses more recent data on fuel used for power generation, electricity generated and imports and exports from Energy Trends, so the lag is one year.
The 2025 set used 2023 data and the 2026 set uses 2025 data, so no published set is built on 2024.
The annual factor still trails the live grid by about a year, which is why the two will never match, and why the live number is context rather than an input.
| Factor set | Data year | UK electricity, kgCO2e/kWh |
|---|---|---|
| 2025 | 2023 | 0.17700 |
| 2026 | 2025 | 0.13096 |
Time-matched Scope 2
Half-hourly data in a carbon report: not yet
Half-hourly intensity matters for market-based claims backed by matched procurement and for 24/7 clean-power commitments, but it sits beside the compliance calculation rather than inside it.
The GHG Protocol consulted on hourly matching as part of its Scope 2 revision, and its July 2026 summary of feedback reported “low support for hourly matching and deliverability as proposed”.
Until any revision is published, the 2015 Scope 2 Guidance governs, and its location-based method uses grid-average factors.
The Corporate Standard requires Scope 1 and Scope 2 as a minimum; how the two Scope 2 methods differ, with REGOs and the residual mix, is on our page on market-based Scope 2 emissions.
If you have half-hourly meter data, it can still sharpen a location-based estimate of when and where you drew power; say so in the methodology note rather than swapping the factor.
Where you are
Regional differences and the forecast
NESO’s regional forecast shows intensity for each part of the network, because the mix feeding each region differs.
That makes it useful for scheduling flexible demand, such as electric-vehicle charging or batch processes, towards lower-carbon periods and places.
For company reporting the DESNZ factor is a single UK figure, so a site in a low-carbon region does not report a lower location-based Scope 2.
The conversion factors collection is the home of that single figure, published each June.
How that factor fits among SECR, ESOS, UK SRS and the rest is mapped in our overview of UK carbon reporting.
Frequently asked
Questions people ask
What is the UK grid carbon intensity right now?
It changes every half hour with the generation mix. NESO's Carbon Intensity API and the carbonintensity.org.uk service publish a forecast and an actual intensity for each half hour in grams of CO2 per kWh, with an index band such as "low", and forecast the carbon intensity and generation mix 96 hours or more ahead, with a regional breakdown.
What was the UK grid carbon intensity in 2025?
DESNZ's Fuel Mix Disclosure data table gives an estimated carbon dioxide emissions intensity of UK generation of 147 g/kWh for 2025. That figure covers only emissions from UK generators in the operational phase, not fuel supply chains or imports, and it aligns with table 5.14 of the Digest of UK Energy Statistics. The equivalent table for the previous period gave 171 g/kWh for 2023.
Is grid carbon intensity the same as the DESNZ electricity conversion factor?
No. The conversion factor is a fixed annual figure for company reporting: 0.13096 kgCO2e per kWh in the 2026 set, built on 2025 data, including imported electricity and expressed in CO2 equivalent. The DESNZ Fuel Mix Disclosure figure is CO2 only from UK generators, and NESO's figure is live and GB-only. They answer different questions, and a carbon report uses the conversion factor.
Can I use half-hourly carbon intensity data in my carbon report?
Not in place of the annual factor for SECR or UK SRS location-based reporting in current UK practice. UK SRS S2 requires location-based Scope 2 and does not name a factor set, but asks for factors that best represent the activity and disclosure of which were used. The GHG Protocol consulted on hourly matching for market-based Scope 2 and reported low support for it as proposed, so it is not a requirement.
Why does carbon intensity vary by region?
Because the mix of generation feeding each part of the network differs, and NESO's regional forecast shows it half hour by half hour. For company reporting, the DESNZ factor is a single UK figure, and regional figures are an operational signal.
What share of UK electricity came from renewables in 2025/26?
DESNZ's Fuel Mix Disclosure data table for April 2025 to March 2026 gives a UK fuel mix of 48.0% renewables, 31.4% natural gas, 13.7% nuclear, 4.7% coal and 2.2% other. That is on an electricity supplied basis with an estimated allocation for imports, so it differs from the generation mix in Energy Trends and DUKES.
Where can I get a half-hourly electricity carbon intensity dashboard?
NESO publishes one: carbonintensity.org.uk shows the national and regional forecast and actual intensity, and the same data is available through its Carbon Intensity API and the NESO data portal.
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.
- NESOCarbon Intensity (carbonintensity.org.uk)
National and regional forecasts 96+ hours ahead; built with EDF Europe, University of Oxford and WWF.
- NESOCarbon Intensity API — /intensity
Half-hour periods, each with forecast, actual and index band, in gCO2/kWh.
- NESONESO data portal
GB system data, including carbon intensity.
- NESOReal-time data dashboard shows Britain's progress decarbonising electricity
NESO's announcement of its live carbon-intensity dashboard.
- DESNZFuel Mix Disclosure data table, 1 April 2025 – 31 March 2026
147 g/kWh CO2 for UK generation in 2025; UK and residual fuel mix; T&D loss factor.
- DESNZFuel Mix Disclosure data table, 2023/24
171 g/kWh CO2 for UK generation in 2023.
- DESNZDUKES Chapter 5: electricity
Table 5.14, the carbon intensity series the Fuel Mix figures align with.
- DESNZEnergy Trends
The generation statistics the 2026 conversion factor now draws on.
- DESNZ2026 conversion factors methodology paper, ¶¶3.1, 3.5–3.8 and Table 9
0.13096 kgCO2e/kWh, data year 2025, including imports; T&D in Scope 3; the one-year lag.
- DESNZGreenhouse gas reporting: conversion factors 2026
The annual factor set for company reporting.
- DESNZUK government conversion factors for company reporting (collection)
Every annual set.
- Department for Business and TradeUK SRS S1 and UK SRS S2
UK SRS S2 ¶29(a)(v) and ¶B29: location-based Scope 2, and factors that best represent the activity.
- legislation.gov.ukSI 2018/1155 — the SECR regulations
The instrument under which the annual factor is applied in directors' reports.
- GHG ProtocolScope 2 Guidance (2015)
Location-based and market-based methods.
- GHG ProtocolA Corporate Accounting and Reporting Standard
Scope 1 and 2 accounting.
- GHG ProtocolScope 2 public consultation: summary of feedback (29 July 2026)
"Low support for hourly matching and deliverability as proposed".
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