In January 2025, Britain's electricity averaged 168 gCO₂/kWh, in the moderate band (140–219 g). That is 31% dirtier than December 2024 (128 g), and about the same as January 2024 (167 g). Gas made 40.9% of the electricity generated, wind 27.7%, nuclear 12.4% and imports 10.3%; low-carbon sources together made 48.8%. The cleanest half hour was 35 g at 10:30 on Wednesday 1 January, and the dirtiest 293 g at 06:00 on Wednesday 22 January. The cleanest day was Wednesday 1 January (59 g on average); the windiest was Sunday 26 January (51.9% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 Jan | 59 | – | – | – | – | 48 |
| Thu 2 Jan | 113 | – | – | – | – | 48 |
| Fri 3 Jan | 138 | 47.2% | 23.8% | 3.2% | 40.7% | 48 |
| Sat 4 Jan | 192 | 40.8% | 17.2% | 0.6% | 46.2% | 48 |
| Sun 5 Jan | 102 | 63.1% | 39.6% | 0.3% | 22.0% | 48 |
| Mon 6 Jan | 94 | 66.7% | 46.7% | 0.9% | 20.7% | 48 |
| Tue 7 Jan | 116 | 61.2% | 41.3% | 1.6% | 26.1% | 48 |
| Wed 8 Jan | 199 | 40.1% | 19.5% | 0.6% | 47.6% | 48 |
| Thu 9 Jan | 183 | 46.4% | 25.6% | 2.2% | 43.5% | 48 |
| Fri 10 Jan | 225 | 33.4% | 12.3% | 1.6% | 54.3% | 48 |
| Sat 11 Jan | 223 | 33.9% | 9.8% | 1.5% | 52.0% | 48 |
| Sun 12 Jan | 196 | 50.9% | 24.9% | 1.7% | 34.5% | 48 |
| Mon 13 Jan | 149 | 58.1% | 41.1% | 1.3% | 37.6% | 48 |
| Tue 14 Jan | 189 | 49.0% | 29.9% | 1.3% | 46.4% | 48 |
| Wed 15 Jan | 223 | 41.0% | 21.9% | 1.6% | 55.2% | 48 |
| Thu 16 Jan | 211 | 44.1% | 26.1% | 1.6% | 51.8% | 48 |
| Fri 17 Jan | 209 | 45.3% | 27.8% | 0.8% | 50.9% | 48 |
| Sat 18 Jan | 227 | 41.1% | 20.9% | 0.6% | 54.5% | 48 |
| Sun 19 Jan | 253 | 30.1% | 9.8% | 0.3% | 61.6% | 48 |
| Mon 20 Jan | 265 | 27.9% | 8.7% | 0.9% | 65.7% | 48 |
| Tue 21 Jan | 256 | 30.0% | 10.3% | 1.1% | 63.1% | 48 |
| Wed 22 Jan | 265 | 23.7% | 2.6% | 1.2% | 64.9% | 48 |
| Thu 23 Jan | 157 | 52.1% | 33.0% | 0.9% | 36.7% | 48 |
| Fri 24 Jan | 86 | 71.2% | 50.9% | 2.0% | 18.6% | 48 |
| Sat 25 Jan | 93 | 67.5% | 42.8% | 3.4% | 19.9% | 48 |
| Sun 26 Jan | 69 | 73.3% | 51.9% | 0.6% | 13.5% | 48 |
| Mon 27 Jan | 87 | 68.9% | 46.6% | 2.0% | 17.4% | 48 |
| Tue 28 Jan | 112 | 63.1% | 41.0% | 1.0% | 23.1% | 48 |
| Wed 29 Jan | 124 | 61.1% | 38.6% | 2.0% | 25.9% | 48 |
| Thu 30 Jan | 167 | 50.8% | 27.9% | 3.7% | 38.2% | 48 |
| Fri 31 Jan | 230 | 34.4% | 12.9% | 1.4% | 53.5% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in January 2025, with January 2024 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 100 hours, 13%
- Low (70–139 g): 160 hours, 21%
- Moderate (140–219 g): 261 hours, 35%
- High (220–299 g): 224 hours, 30%
Records in January 2025
- Cleanest half hour
- 35 g 10:30 on Wednesday 1 January
- Dirtiest half hour
- 293 g 06:00 on Wednesday 22 January
- Most wind
- 67.6% 02:30 on Friday 24 January
- Most solar
- 17.2% 12:00 on Thursday 30 January
- Most low-carbon
- 85.0% 02:30 on Friday 24 January
- Least gas
- 6.0% 23:00 on Monday 27 January
- Cleanest day
- 59 g Wednesday 1 January
- Dirtiest day
- 265 g Monday 20 January
- Windiest day
- 51.9% wind Sunday 26 January
- Sunniest day
- 3.7% solar Thursday 30 January
About these figures
GridMonkey records NESO's carbon intensity and generation mix for Great Britain every half hour: the actual figure where NESO has published one, otherwise its forecast. They are added up by UK calendar day and month. Percentages are shares of the electricity generated, imports included, so the fuels add up to 100%. Low-carbon means wind, solar, nuclear, biomass and hydro. The carbon bands are GridMonkey's: very low under 70 g, low 70–139 g, moderate 140–219 g, high 220–299 g and very high 300 g or more, per kWh. Northern Ireland has its own grid and isn't included.
To see the grid now, open GridMonkey. For the wind farms that ran hardest this week, see the wind farm league table.
Data: NESO Carbon Intensity API (carbonintensity.org.uk), licensed under CC BY 4.0, recorded and summarised by GridMonkey. Figures as of 20 October 2026.