In August 2025, Britain's electricity averaged 124 gCO₂/kWh, in the low band (70–139 g). That is 4% cleaner than July 2025 (129 g), and 48% dirtier than August 2024 (84 g). Wind made 27.7% of the electricity generated, gas 25.6%, imports 15.8% and nuclear 12.6%; low-carbon sources together made 58.5%. The cleanest half hour was 34 g at 13:00 on Sunday 31 August, and the dirtiest 242 g at 21:30 on Tuesday 12 August. Sunday 31 August was both the cleanest day (59 g on average) and the windiest (57.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Fri 1 Aug | 78 | 69.3% | 37.2% | 8.4% | 13.7% | 48 |
| Sat 2 Aug | 84 | 64.4% | 27.2% | 12.3% | 13.6% | 48 |
| Sun 3 Aug | 95 | 62.1% | 33.6% | 8.8% | 17.0% | 48 |
| Mon 4 Aug | 80 | 73.4% | 50.0% | 6.2% | 16.4% | 48 |
| Tue 5 Aug | 71 | 79.3% | 53.9% | 10.6% | 15.1% | 48 |
| Wed 6 Aug | 94 | 64.5% | 31.5% | 12.5% | 17.7% | 48 |
| Thu 7 Aug | 87 | 69.6% | 44.1% | 8.0% | 17.3% | 48 |
| Fri 8 Aug | 90 | 67.2% | 37.7% | 11.7% | 18.8% | 48 |
| Sat 9 Aug | 81 | 72.5% | 42.2% | 12.2% | 17.1% | 48 |
| Sun 10 Aug | 108 | 60.8% | 22.0% | 16.8% | 19.6% | 48 |
| Mon 11 Aug | 155 | 47.0% | 15.3% | 11.6% | 35.0% | 48 |
| Tue 12 Aug | 178 | 43.5% | 11.3% | 11.4% | 39.6% | 48 |
| Wed 13 Aug | 189 | 42.2% | 12.6% | 8.9% | 43.4% | 48 |
| Thu 14 Aug | 168 | 46.8% | 17.7% | 8.7% | 37.5% | 48 |
| Fri 15 Aug | 147 | 50.8% | 16.8% | 12.2% | 30.9% | 48 |
| Sat 16 Aug | 137 | 49.7% | 16.9% | 9.4% | 26.7% | 48 |
| Sun 17 Aug | 121 | 54.1% | 14.6% | 14.9% | 23.5% | 48 |
| Mon 18 Aug | 187 | 41.5% | 13.0% | 5.1% | 41.6% | 48 |
| Tue 19 Aug | 147 | 52.4% | 25.0% | 5.7% | 31.7% | 48 |
| Wed 20 Aug | 140 | 55.7% | 30.2% | 6.0% | 30.2% | 48 |
| Thu 21 Aug | 156 | 48.4% | 19.5% | 8.2% | 33.4% | 48 |
| Fri 22 Aug | 175 | 42.4% | 8.8% | 9.6% | 37.6% | 48 |
| Sat 23 Aug | 173 | 40.6% | 5.8% | 8.3% | 36.1% | 48 |
| Sun 24 Aug | 158 | 42.5% | 7.6% | 11.2% | 31.8% | 48 |
| Mon 25 Aug | 113 | 64.5% | 28.9% | 14.0% | 21.2% | 48 |
| Tue 26 Aug | 117 | 61.8% | 33.1% | 8.9% | 26.8% | 48 |
| Wed 27 Aug | 124 | 63.4% | 33.6% | 7.8% | 25.4% | 48 |
| Thu 28 Aug | 118 | 63.4% | 32.5% | 8.1% | 24.7% | 48 |
| Fri 29 Aug | 123 | 61.2% | 30.5% | 8.2% | 24.5% | 48 |
| Sat 30 Aug | 84 | 73.4% | 44.4% | 7.0% | 15.3% | 48 |
| Sun 31 Aug | 59 | 83.9% | 57.8% | 10.1% | 12.5% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in August 2025, with August 2024 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 110 hours, 15%
- Low (70–139 g): 332 hours, 45%
- Moderate (140–219 g): 296 hours, 40%
- High (220–299 g): 7 hours, 1%
Records in August 2025
- Cleanest half hour
- 34 g 13:00 on Sunday 31 August
- Dirtiest half hour
- 242 g 21:30 on Tuesday 12 August
- Most wind
- 70.3% 23:00 on Saturday 30 August
- Most solar
- 43.3% 12:30 on Sunday 17 August
- Most low-carbon
- 91.0% 14:30 on Sunday 31 August
- Least gas
- 5.5% 12:30 on Wednesday 6 August
- Cleanest day
- 59 g Sunday 31 August
- Dirtiest day
- 189 g Wednesday 13 August
- Windiest day
- 57.8% wind Sunday 31 August
- Sunniest day
- 16.8% solar Sunday 10 August
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.