In July 2025, Britain's electricity averaged 129 gCO₂/kWh, in the low band (70–139 g). That is 30% dirtier than June 2025 (99 g), and 12% dirtier than July 2024 (115 g). Gas made 27.3% of the electricity generated, wind 20.7%, nuclear 16.4% and imports 16.3%; low-carbon sources together made 56.4%. The cleanest half hour was 33 g at 14:00 on Friday 4 July, and the dirtiest 233 g at 21:30 on Tuesday 1 July. Saturday 5 July was both the cleanest day (65 g on average) and the windiest (54.1% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Tue 1 Jul | 180 | 48.7% | 14.5% | 8.8% | 40.5% | 48 |
| Wed 2 Jul | 162 | 54.1% | 16.8% | 9.8% | 35.8% | 48 |
| Thu 3 Jul | 108 | 68.3% | 24.6% | 13.4% | 20.6% | 48 |
| Fri 4 Jul | 78 | 77.3% | 40.8% | 11.3% | 14.3% | 48 |
| Sat 5 Jul | 65 | 80.7% | 54.1% | 7.1% | 13.0% | 48 |
| Sun 6 Jul | 113 | 57.0% | 24.5% | 9.1% | 24.2% | 48 |
| Mon 7 Jul | 71 | 73.0% | 41.2% | 11.1% | 14.3% | 48 |
| Tue 8 Jul | 93 | 67.3% | 26.7% | 15.0% | 18.0% | 48 |
| Wed 9 Jul | 149 | 50.7% | 13.4% | 12.5% | 32.7% | 48 |
| Thu 10 Jul | 156 | 51.3% | 9.4% | 15.0% | 33.8% | 48 |
| Fri 11 Jul | 160 | 47.6% | 6.9% | 14.7% | 34.6% | 48 |
| Sat 12 Jul | 123 | 56.5% | 12.0% | 16.1% | 24.1% | 48 |
| Sun 13 Jul | 113 | 61.2% | 17.0% | 14.6% | 21.2% | 48 |
| Mon 14 Jul | 90 | 68.6% | 34.5% | 9.9% | 17.3% | 48 |
| Tue 15 Jul | 78 | 70.2% | 37.4% | 7.1% | 12.6% | 48 |
| Wed 16 Jul | 142 | 52.3% | 15.1% | 10.7% | 29.8% | 48 |
| Thu 17 Jul | 170 | 47.0% | 12.3% | 7.6% | 37.2% | 48 |
| Fri 18 Jul | 150 | 52.2% | 17.1% | 10.6% | 33.1% | 48 |
| Sat 19 Jul | 145 | 48.6% | 19.1% | 6.3% | 32.0% | 48 |
| Sun 20 Jul | 118 | 55.1% | 22.0% | 8.4% | 24.6% | 48 |
| Mon 21 Jul | 154 | 46.4% | 12.0% | 9.7% | 34.0% | 48 |
| Tue 22 Jul | 152 | 47.1% | 18.0% | 7.3% | 33.6% | 48 |
| Wed 23 Jul | 149 | 48.8% | 14.6% | 8.2% | 32.1% | 48 |
| Thu 24 Jul | 138 | 52.6% | 21.0% | 7.9% | 30.3% | 48 |
| Fri 25 Jul | 140 | 52.7% | 15.3% | 12.2% | 31.5% | 48 |
| Sat 26 Jul | 122 | 54.3% | 17.4% | 9.4% | 25.2% | 48 |
| Sun 27 Jul | 118 | 53.6% | 22.2% | 7.8% | 24.7% | 48 |
| Mon 28 Jul | 127 | 53.6% | 18.2% | 10.4% | 25.5% | 48 |
| Tue 29 Jul | 177 | 41.5% | 6.0% | 7.5% | 38.6% | 48 |
| Wed 30 Jul | 150 | 51.3% | 14.0% | 9.7% | 31.6% | 48 |
| Thu 31 Jul | 119 | 59.5% | 24.6% | 8.3% | 24.2% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in July 2025, with July 2024 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 80 hours, 11%
- Low (70–139 g): 338 hours, 45%
- Moderate (140–219 g): 321 hours, 43%
- High (220–299 g): 6 hours, 1%
Records in July 2025
- Cleanest half hour
- 33 g 14:00 on Friday 4 July
- Dirtiest half hour
- 233 g 21:30 on Tuesday 1 July
- Most wind
- 65.0% 03:00 on Saturday 5 July
- Most solar
- 44.4% 12:30 on Saturday 12 July
- Most low-carbon
- 94.9% 14:00 on Friday 4 July
- Least gas
- 4.3% 14:00 on Friday 4 July
- Cleanest day
- 65 g Saturday 5 July
- Dirtiest day
- 180 g Tuesday 1 July
- Windiest day
- 54.1% wind Saturday 5 July
- Sunniest day
- 16.1% solar Saturday 12 July
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.