In October 2025, Britain's electricity averaged 138 gCO₂/kWh, in the low band (70–139 g). That is 23% dirtier than September 2025 (112 g), and about the same as October 2024 (138 g). Wind made 37.2% of the electricity generated, gas 30.9%, nuclear 11.6% and imports 10.9%; low-carbon sources together made 58.2%. The cleanest half hour was 32 g at 10:00 on Tuesday 28 October, and the dirtiest 279 g at 06:30 on Tuesday 14 October. The cleanest day was Sunday 26 October (53 g on average); the windiest was Saturday 4 October (69.6% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Thu 2 Oct | 103 | 67.8% | 47.2% | 5.2% | 20.9% | 33 |
| Fri 3 Oct | 80 | 75.4% | 62.7% | 1.0% | 17.3% | 48 |
| Sat 4 Oct | 62 | 85.4% | 69.6% | 5.1% | 12.2% | 48 |
| Sun 5 Oct | 60 | 80.9% | 64.9% | 6.0% | 11.5% | 48 |
| Mon 6 Oct | 118 | 64.1% | 43.1% | 6.9% | 27.2% | 48 |
| Tue 7 Oct | 174 | 50.7% | 32.1% | 3.2% | 42.2% | 48 |
| Wed 8 Oct | 198 | 44.0% | 23.8% | 3.4% | 48.9% | 48 |
| Thu 9 Oct | 154 | 54.1% | 31.9% | 4.2% | 35.0% | 48 |
| Fri 10 Oct | 187 | 42.6% | 22.3% | 2.6% | 43.0% | 48 |
| Sat 11 Oct | 210 | 34.9% | 12.8% | 4.3% | 46.9% | 48 |
| Sun 12 Oct | 238 | 27.6% | 4.8% | 3.9% | 54.8% | 48 |
| Mon 13 Oct | 263 | 25.0% | 6.1% | 1.8% | 64.2% | 48 |
| Tue 14 Oct | 257 | 27.6% | 8.3% | 1.5% | 62.5% | 48 |
| Wed 15 Oct | 243 | 30.8% | 10.4% | 1.7% | 58.7% | 48 |
| Thu 16 Oct | 232 | 32.5% | 9.9% | 2.5% | 55.3% | 48 |
| Fri 17 Oct | 241 | 29.0% | 6.0% | 2.1% | 58.8% | 48 |
| Sat 18 Oct | 144 | 53.3% | 28.4% | 2.0% | 32.3% | 48 |
| Sun 19 Oct | 66 | 77.0% | 57.5% | 1.4% | 11.6% | 48 |
| Mon 20 Oct | 143 | 53.1% | 29.2% | 2.4% | 30.7% | 48 |
| Tue 21 Oct | 100 | 67.3% | 40.1% | 3.2% | 18.4% | 48 |
| Wed 22 Oct | 167 | 49.9% | 25.0% | 4.0% | 39.7% | 48 |
| Thu 23 Oct | 74 | 72.7% | 47.8% | 2.7% | 11.1% | 48 |
| Fri 24 Oct | 63 | 78.6% | 56.7% | 4.7% | 9.4% | 48 |
| Sat 25 Oct | 56 | 83.1% | 64.9% | 4.6% | 11.3% | 48 |
| Sun 26 Oct | 53 | 78.7% | 61.3% | 1.2% | 9.3% | 50 |
| Mon 27 Oct | 84 | 73.0% | 49.7% | 4.1% | 16.3% | 48 |
| Tue 28 Oct | 59 | 81.0% | 59.7% | 4.0% | 10.6% | 48 |
| Wed 29 Oct | 121 | 64.0% | 40.5% | 2.1% | 27.0% | 48 |
| Thu 30 Oct | 121 | 62.8% | 38.8% | 2.8% | 25.6% | 48 |
| Fri 31 Oct | 66 | 80.4% | 61.2% | 1.6% | 13.5% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in October 2025, with October 2024 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 211 hours, 30%
- Low (70–139 g): 176 hours, 25%
- Moderate (140–219 g): 171 hours, 24%
- High (220–299 g): 156 hours, 22%
Records in October 2025
- Cleanest half hour
- 32 g 10:00 on Tuesday 28 October
- Dirtiest half hour
- 279 g 06:30 on Tuesday 14 October
- Most wind
- 76.0% 22:30 on Saturday 4 October
- Most solar
- 25.9% 12:30 on Monday 6 October
- Most low-carbon
- 92.0% 03:30 on Monday 27 October
- Least gas
- 4.1% 10:30 on Tuesday 28 October
- Cleanest day
- 53 g Sunday 26 October
- Dirtiest day
- 263 g Monday 13 October
- Windiest day
- 69.6% wind Saturday 4 October
- Sunniest day
- 6.9% solar Monday 6 October
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 19 October 2026.