In August 2026, Britain's electricity averaged 125 gCO₂/kWh, in the low band (70–139 g). That is 2% dirtier than July 2026 (122 g), and about the same as August 2025 (124 g). Wind made 23.7% of the electricity generated, gas 23.6%, nuclear 14.9% and imports 14.4%; low-carbon sources together made 59.7%. The cleanest half hour was 34 g at 11:30 on Thursday 6 August, and the dirtiest 243 g at 04:30 on Monday 17 August. Wednesday 5 August was both the cleanest day (65 g on average) and the windiest (49.0% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Sat 1 Aug | 112 | 57.3% | 22.7% | 13.8% | 20.7% | 48 |
| Sun 2 Aug | 129 | 52.3% | 11.0% | 16.2% | 21.8% | 48 |
| Mon 3 Aug | 121 | 60.2% | 24.1% | 13.6% | 22.5% | 48 |
| Tue 4 Aug | 129 | 60.5% | 28.7% | 9.4% | 26.0% | 48 |
| Wed 5 Aug | 65 | 79.8% | 49.0% | 9.7% | 10.9% | 48 |
| Thu 6 Aug | 101 | 67.9% | 34.1% | 10.2% | 18.2% | 48 |
| Fri 7 Aug | 126 | 59.9% | 24.5% | 13.4% | 23.5% | 48 |
| Sat 8 Aug | 94 | 66.5% | 28.7% | 14.9% | 16.9% | 48 |
| Sun 9 Aug | 96 | 64.1% | 26.5% | 14.2% | 16.4% | 48 |
| Mon 10 Aug | 136 | 55.2% | 18.3% | 13.5% | 26.0% | 48 |
| Tue 11 Aug | 123 | 56.5% | 18.6% | 14.5% | 22.3% | 48 |
| Wed 12 Aug | 125 | 60.9% | 26.1% | 13.3% | 24.6% | 48 |
| Thu 13 Aug | 184 | 41.9% | 9.0% | 13.0% | 38.5% | 48 |
| Fri 14 Aug | 169 | 48.0% | 14.6% | 11.6% | 34.6% | 48 |
| Sat 15 Aug | 125 | 56.8% | 19.1% | 12.4% | 23.3% | 48 |
| Sun 16 Aug | 171 | 44.3% | 4.9% | 11.6% | 33.8% | 48 |
| Mon 17 Aug | 207 | 41.1% | 7.6% | 8.1% | 45.4% | 48 |
| Tue 18 Aug | 150 | 60.3% | 29.9% | 7.2% | 33.5% | 48 |
| Wed 19 Aug | 175 | 50.8% | 17.0% | 8.5% | 38.1% | 48 |
| Thu 20 Aug | 149 | 56.0% | 25.0% | 7.8% | 31.6% | 48 |
| Fri 21 Aug | 131 | 57.9% | 24.7% | 8.9% | 26.5% | 48 |
| Sat 22 Aug | 82 | 63.8% | 24.6% | 11.5% | 10.1% | 48 |
| Sun 23 Aug | 113 | 53.4% | 8.3% | 14.1% | 15.1% | 48 |
| Mon 24 Aug | 111 | 62.2% | 21.8% | 12.1% | 18.6% | 48 |
| Tue 25 Aug | 80 | 77.3% | 38.7% | 10.7% | 12.1% | 48 |
| Wed 26 Aug | 107 | 70.3% | 34.4% | 8.8% | 19.4% | 48 |
| Thu 27 Aug | 147 | 60.6% | 24.6% | 6.3% | 27.2% | 48 |
| Fri 28 Aug | 102 | 69.1% | 31.8% | 7.6% | 16.1% | 48 |
| Sat 29 Aug | 110 | 63.9% | 27.9% | 5.6% | 15.9% | 48 |
| Sun 30 Aug | 107 | 63.5% | 21.7% | 8.2% | 16.6% | 48 |
| Mon 31 Aug | 106 | 68.7% | 36.6% | 8.4% | 26.4% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in August 2026, with August 2025 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 128 hours, 17%
- Low (70–139 g): 318 hours, 43%
- Moderate (140–219 g): 280 hours, 38%
- High (220–299 g): 19 hours, 2%
Records in August 2026
- Cleanest half hour
- 34 g 11:30 on Thursday 6 August
- Dirtiest half hour
- 243 g 04:30 on Monday 17 August
- Most wind
- 61.8% 04:00 on Thursday 6 August
- Most solar
- 43.3% 12:00 on Sunday 2 August
- Most low-carbon
- 89.1% 04:00 on Thursday 6 August
- Least gas
- 3.4% 12:30 on Tuesday 25 August
- Cleanest day
- 65 g Wednesday 5 August
- Dirtiest day
- 207 g Monday 17 August
- Windiest day
- 49.0% wind Wednesday 5 August
- Sunniest day
- 16.2% solar Sunday 2 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 17 October 2026.