In June 2025, Britain's electricity averaged 99 gCO₂/kWh, in the low band (70–139 g). That is 7% cleaner than May 2025 (107 g), and 1% cleaner than June 2024 (100 g). Wind made 34.2% of the electricity generated, gas 19.8%, nuclear 16.5% and imports 11.2%; low-carbon sources together made 69.0%. The cleanest half hour was 31 g at 13:00 on Tuesday 3 June, and the dirtiest 231 g at 21:30 on Tuesday 10 June. The cleanest day was Sunday 22 June (56 g on average); the windiest was Tuesday 3 June (56.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Sun 1 Jun | 60 | 80.0% | 47.0% | 10.9% | 11.5% | 48 |
| Mon 2 Jun | 81 | 71.0% | 36.3% | 13.5% | 16.0% | 48 |
| Tue 3 Jun | 60 | 82.4% | 56.8% | 7.7% | 13.2% | 48 |
| Wed 4 Jun | 83 | 72.3% | 43.9% | 10.1% | 18.6% | 48 |
| Thu 5 Jun | 99 | 67.2% | 36.0% | 6.3% | 18.5% | 48 |
| Fri 6 Jun | 107 | 64.6% | 26.3% | 11.4% | 18.6% | 48 |
| Sat 7 Jun | 131 | 55.8% | 18.7% | 8.3% | 25.8% | 48 |
| Sun 8 Jun | 84 | 69.7% | 37.1% | 11.6% | 16.0% | 48 |
| Mon 9 Jun | 116 | 61.9% | 29.0% | 8.4% | 23.4% | 48 |
| Tue 10 Jun | 107 | 68.4% | 33.4% | 11.3% | 20.2% | 48 |
| Wed 11 Jun | 138 | 57.4% | 20.2% | 13.0% | 29.5% | 48 |
| Thu 12 Jun | 91 | 74.7% | 48.3% | 7.8% | 18.5% | 48 |
| Fri 13 Jun | 126 | 61.3% | 26.9% | 12.1% | 25.4% | 48 |
| Sat 14 Jun | 84 | 71.2% | 33.5% | 11.7% | 14.8% | 48 |
| Sun 15 Jun | 89 | 69.6% | 31.1% | 12.6% | 16.6% | 48 |
| Mon 16 Jun | 98 | 68.5% | 29.3% | 12.5% | 18.6% | 48 |
| Tue 17 Jun | 101 | 68.6% | 30.0% | 12.3% | 19.5% | 48 |
| Wed 18 Jun | 140 | 57.2% | 15.4% | 13.2% | 29.8% | 48 |
| Thu 19 Jun | 150 | 55.0% | 11.8% | 14.1% | 32.1% | 48 |
| Fri 20 Jun | 118 | 64.3% | 24.4% | 11.9% | 24.0% | 48 |
| Sat 21 Jun | 91 | 70.6% | 32.7% | 10.0% | 17.0% | 48 |
| Sun 22 Jun | 56 | 82.9% | 51.1% | 9.2% | 11.1% | 48 |
| Mon 23 Jun | 62 | 83.6% | 53.9% | 10.0% | 11.9% | 48 |
| Tue 24 Jun | 63 | 80.1% | 49.0% | 7.4% | 10.9% | 48 |
| Wed 25 Jun | 160 | 53.2% | 16.5% | 8.9% | 35.9% | 48 |
| Thu 26 Jun | 81 | 74.0% | 40.3% | 9.8% | 17.2% | 48 |
| Fri 27 Jun | 71 | 79.2% | 46.1% | 10.1% | 14.6% | 48 |
| Sat 28 Jun | 66 | 82.7% | 51.8% | 9.9% | 14.1% | 48 |
| Sun 29 Jun | 112 | 61.6% | 23.6% | 11.6% | 22.2% | 48 |
| Mon 30 Jun | 134 | 61.0% | 25.4% | 11.4% | 28.6% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in June 2025, with June 2024 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 201 hours, 28%
- Low (70–139 g): 395 hours, 55%
- Moderate (140–219 g): 122 hours, 17%
- High (220–299 g): 3 hours, 0%
Records in June 2025
- Cleanest half hour
- 31 g 13:00 on Tuesday 3 June
- Dirtiest half hour
- 231 g 21:30 on Tuesday 10 June
- Most wind
- 68.1% 04:30 on Tuesday 3 June
- Most solar
- 38.8% 13:00 on Thursday 19 June
- Most low-carbon
- 92.7% 15:00 on Sunday 1 June
- Least gas
- 4.9% 12:00 on Tuesday 24 June
- Cleanest day
- 56 g Sunday 22 June
- Dirtiest day
- 160 g Wednesday 25 June
- Windiest day
- 56.8% wind Tuesday 3 June
- Sunniest day
- 14.1% solar Thursday 19 June
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.