In April 2025, Britain's electricity averaged 133 gCO₂/kWh, in the low band (70–139 g). That is 9% cleaner than March 2025 (146 g), and 43% dirtier than April 2024 (93 g). Gas made 28.2% of the electricity generated, wind 24.6%, imports 14.7% and nuclear 14.6%; low-carbon sources together made 57.1%. The cleanest half hour was 34 g at 13:00 on Wednesday 16 April, and the dirtiest 251 g at 20:30 on Monday 7 April. The cleanest day was Saturday 5 April (67 g on average); the windiest was Wednesday 16 April (47.4% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Tue 1 Apr | 80 | 71.9% | 39.3% | 16.2% | 13.9% | 33 |
| Wed 2 Apr | 69 | 75.6% | 46.4% | 10.6% | 11.2% | 48 |
| Thu 3 Apr | 81 | 72.4% | 43.7% | 9.5% | 14.8% | 48 |
| Fri 4 Apr | 76 | 74.0% | 42.6% | 9.0% | 13.2% | 48 |
| Sat 5 Apr | 67 | 75.7% | 42.6% | 12.2% | 10.6% | 48 |
| Sun 6 Apr | 98 | 64.7% | 30.1% | 13.1% | 17.7% | 48 |
| Mon 7 Apr | 183 | 45.1% | 9.0% | 11.7% | 41.9% | 48 |
| Tue 8 Apr | 207 | 39.0% | 4.8% | 10.7% | 49.0% | 48 |
| Wed 9 Apr | 178 | 46.8% | 13.0% | 9.6% | 39.4% | 48 |
| Thu 10 Apr | 154 | 53.5% | 16.7% | 10.7% | 33.2% | 48 |
| Fri 11 Apr | 147 | 55.3% | 16.5% | 11.9% | 32.1% | 48 |
| Sat 12 Apr | 107 | 61.9% | 24.1% | 9.6% | 19.5% | 48 |
| Sun 13 Apr | 87 | 66.6% | 31.7% | 8.5% | 15.0% | 48 |
| Mon 14 Apr | 104 | 65.2% | 32.7% | 7.0% | 20.1% | 48 |
| Tue 15 Apr | 165 | 47.5% | 16.5% | 4.1% | 35.5% | 48 |
| Wed 16 Apr | 72 | 74.2% | 47.4% | 7.0% | 15.2% | 48 |
| Thu 17 Apr | 148 | 53.6% | 17.7% | 10.3% | 33.0% | 48 |
| Fri 18 Apr | 96 | 66.1% | 34.3% | 5.5% | 17.2% | 48 |
| Sat 19 Apr | 77 | 70.0% | 43.5% | 7.8% | 14.7% | 48 |
| Sun 20 Apr | 139 | 52.2% | 16.2% | 11.6% | 28.7% | 48 |
| Mon 21 Apr | 173 | 44.2% | 16.4% | 5.9% | 39.7% | 48 |
| Tue 22 Apr | 178 | 44.6% | 14.2% | 10.0% | 41.5% | 48 |
| Wed 23 Apr | 198 | 40.0% | 15.0% | 6.1% | 47.1% | 48 |
| Thu 24 Apr | 180 | 45.4% | 16.0% | 9.0% | 41.5% | 48 |
| Fri 25 Apr | 161 | 49.5% | 20.7% | 8.2% | 36.4% | 48 |
| Sat 26 Apr | 135 | 51.4% | 21.0% | 8.7% | 28.1% | 48 |
| Sun 27 Apr | 87 | 67.5% | 33.7% | 12.9% | 16.5% | 48 |
| Mon 28 Apr | 152 | 53.5% | 17.9% | 12.5% | 32.3% | 48 |
| Tue 29 Apr | 186 | 44.5% | 8.4% | 13.4% | 41.9% | 48 |
| Wed 30 Apr | 182 | 45.2% | 9.3% | 13.4% | 41.1% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in April 2025, with April 2024 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, 18%
- Low (70–139 g): 268 hours, 38%
- Moderate (140–219 g): 271 hours, 38%
- High (220–299 g): 46 hours, 6%
Records in April 2025
- Cleanest half hour
- 34 g 13:00 on Wednesday 16 April
- Dirtiest half hour
- 251 g 20:30 on Monday 7 April
- Most wind
- 62.1% 00:30 on Wednesday 2 April
- Most solar
- 40.3% 13:00 on Sunday 6 April
- Most low-carbon
- 91.1% 14:30 on Saturday 5 April
- Least gas
- 4.7% 13:00 on Wednesday 2 April
- Cleanest day
- 67 g Saturday 5 April
- Dirtiest day
- 207 g Tuesday 8 April
- Windiest day
- 47.4% wind Wednesday 16 April
- Sunniest day
- 13.4% solar Tuesday 29 April
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 20 October 2026.