In October 2023, Britain's electricity averaged 139 gCO₂/kWh, in the low band (70–139 g). That is 12% cleaner than September 2023 (158 g), and 11% cleaner than October 2022 (156 g). Wind made 35.5% of the electricity generated, gas 27.4%, nuclear 15.0% and imports 8.8%; low-carbon sources together made 62.4%. The cleanest half hour was 34 g at 12:00 on Tuesday 3 October, and the dirtiest 281 g at 06:00 on Thursday 12 October. The cleanest day was Tuesday 3 October (67 g on average); the windiest was Wednesday 18 October (59.1% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Sun 1 Oct | 114 | 66.8% | 39.2% | 2.8% | 24.0% | 48 |
| Mon 2 Oct | 200 | 45.3% | 18.9% | 1.8% | 45.0% | 48 |
| Tue 3 Oct | 67 | 77.5% | 51.8% | 4.9% | 14.4% | 48 |
| Wed 4 Oct | 83 | 76.6% | 50.9% | 3.6% | 17.9% | 48 |
| Thu 5 Oct | 121 | 67.1% | 41.7% | 2.8% | 27.7% | 48 |
| Fri 6 Oct | 77 | 77.6% | 52.3% | 3.8% | 15.5% | 48 |
| Sat 7 Oct | 89 | 70.0% | 43.5% | 4.9% | 18.3% | 48 |
| Sun 8 Oct | 134 | 57.7% | 26.9% | 5.3% | 30.2% | 48 |
| Mon 9 Oct | 203 | 46.7% | 17.5% | 4.0% | 45.4% | 48 |
| Tue 10 Oct | 125 | 66.1% | 39.3% | 3.5% | 29.0% | 48 |
| Wed 11 Oct | 115 | 66.2% | 40.7% | 1.6% | 23.3% | 48 |
| Thu 12 Oct | 227 | 41.1% | 13.3% | 2.2% | 46.4% | 48 |
| Fri 13 Oct | 91 | 75.0% | 48.7% | 2.2% | 12.9% | 48 |
| Sat 14 Oct | 69 | 79.6% | 52.2% | 5.5% | 11.2% | 48 |
| Sun 15 Oct | 121 | 63.9% | 33.1% | 6.1% | 20.0% | 48 |
| Mon 16 Oct | 234 | 40.2% | 12.1% | 2.9% | 46.2% | 48 |
| Tue 17 Oct | 141 | 64.2% | 35.6% | 4.0% | 28.3% | 48 |
| Wed 18 Oct | 68 | 82.3% | 59.1% | 1.6% | 11.8% | 48 |
| Thu 19 Oct | 118 | 76.3% | 51.2% | 2.6% | 20.6% | 48 |
| Fri 20 Oct | 86 | 79.5% | 56.6% | 1.0% | 14.7% | 46 |
| Sun 22 Oct | 246 | 36.8% | 7.7% | 0.9% | 44.6% | 7 |
| Mon 23 Oct | 218 | 46.8% | 19.4% | 2.3% | 41.6% | 48 |
| Tue 24 Oct | 197 | 49.1% | 22.3% | 2.3% | 39.1% | 48 |
| Wed 25 Oct | 220 | 42.1% | 15.4% | 2.5% | 43.5% | 48 |
| Thu 26 Oct | 196 | 50.5% | 25.2% | 2.2% | 39.7% | 48 |
| Fri 27 Oct | 182 | 51.0% | 23.5% | 2.2% | 34.8% | 48 |
| Sat 28 Oct | 109 | 68.2% | 38.9% | 2.2% | 15.6% | 48 |
| Sun 29 Oct | 89 | 74.6% | 49.6% | 2.4% | 13.3% | 50 |
| Mon 30 Oct | 157 | 60.4% | 33.4% | 2.3% | 30.1% | 48 |
| Tue 31 Oct | 161 | 55.5% | 27.1% | 1.9% | 27.8% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in October 2023, with October 2022 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 120 hours, 17%
- Low (70–139 g): 267 hours, 38%
- Moderate (140–219 g): 204 hours, 29%
- High (220–299 g): 110 hours, 16%
Records in October 2023
- Cleanest half hour
- 34 g 12:00 on Tuesday 3 October
- Dirtiest half hour
- 281 g 06:00 on Thursday 12 October
- Most wind
- 66.1% 02:30 on Wednesday 18 October
- Most solar
- 24.3% 12:30 on Sunday 15 October
- Most low-carbon
- 88.6% 13:00 on Wednesday 4 October
- Least gas
- 6.1% 12:00 on Wednesday 4 October
- Cleanest day
- 67 g Tuesday 3 October
- Dirtiest day
- 234 g Monday 16 October
- Windiest day
- 59.1% wind Wednesday 18 October
- Sunniest day
- 6.1% solar Sunday 15 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 23 October 2026.