UK grid carbon intensity: what the number is, and what it isn't
Every kilowatt-hour drawn from the grid carries a carbon cost that changes by the half hour.
In 2025 the average was 126 gCO2/kWh — 2% above 2024's record low.
This page explains where the number comes from, why it moved, and how it relates to the DESNZ electricity factor your carbon report actually uses.
Where the 2025 number landed
UK electricity supplied in 2025 averaged around 126 grams of carbon dioxide per kilowatt-hour — up 2% on the record low of 124 gCO2/kWh set in 2024[1].
The direction of the one-year move is less important than what produced it: renewables set a record at 47% of supplies — 58% counting all low-carbon sources — but a weak wind year pulled gas generation up to fill the gap[1]. Intensity is a mix story, and the mix still swings on the weather.
For the live picture, NESO publishes half-hourly grid carbon intensity and a multi-day forecast through its public dashboard and API[2].
Grid intensity is not your Scope 2 factor
The number your carbon report uses is the DESNZ electricity conversion factor for the matching year-set — the fixed annual figure behind location-based Scope 2 under SECR and UK SRS[3]. It is built from historical inventory data, so it lags the live grid by roughly two years: a report prepared on the current factor reflects a grid that was dirtier than today’s.
The GHG Protocol’s dual-reporting model is what keeps the two numbers straight: location-based Scope 2 uses the average grid factor; market-based Scope 2 reflects your contracted supply[4]. Live intensity data informs strategy — when to shift flexible load, what a 24/7 clean-power claim would take — but the compliance calculation runs on the published factor. Our UK emissions factors reference covers choosing and applying the right year-set.
UK grid carbon intensity: frequently asked questions
What is the UK grid carbon intensity right now?
Grid carbon intensity changes every half hour with the generation mix. NESO (the National Energy System Operator) publishes a live figure and 96-hour forecast through its Carbon Intensity API and dashboard. As an annual benchmark, UK electricity supplied in 2025 averaged around 126 gCO2 per kWh, 2% above the record low of 124 gCO2/kWh set in 2024.
Why did grid carbon intensity rise in 2025 if renewables hit a record?
Renewables supplied a record 47% of UK electricity in 2025 — 58% counting all low-carbon sources — but a weak year for wind meant gas generation rose to fill the gap, nudging average intensity up 2% from 2024’s record low. The long-run trend remains steeply downward as offshore wind capacity builds.
Is grid carbon intensity the same as the DESNZ electricity conversion factor?
No, and confusing them is a common reporting error. The DESNZ conversion factor for purchased electricity is a fixed annual figure used for location-based Scope 2 in SECR and UK SRS reporting, built from historical inventory data — it lags the live grid by roughly two years. Live or annual NESO intensity figures are operational data: useful for load-shifting and context, but your carbon report uses the DESNZ factor for the matching year-set.
Can I use half-hourly carbon intensity data in my carbon report?
For standard SECR and UK SRS location-based reporting, no — you apply the published DESNZ annual factor. Half-hourly data matters for market-based claims backed by matched procurement, for demand-shifting strategies, and increasingly for 24/7 carbon-free energy commitments, but it sits alongside the compliance calculation rather than inside it.
- Analysis: UK renewables enjoy record year in 2025 — but gas power still rises — Carbon Brief · 2025 average 126 gCO2/kWh; 2024 record low 124 gCO2/kWh; renewables 47% and low-carbon 58% of 2025 supplies
- Carbon intensity data dashboard — NESO (National Energy System Operator) · Live and forecast grid carbon intensity for Great Britain
- Government conversion factors for company reporting of greenhouse gas emissions — GOV.UK / DESNZ · The annual electricity factor used for location-based Scope 2 reporting
- GHG Protocol Scope 2 Guidance — Greenhouse Gas Protocol · Defines location-based and market-based methods