In December 2024, Britain's electricity averaged 128 gCO₂/kWh, in the low band (70–139 g). That is 25% cleaner than November 2024 (171 g), and 4% dirtier than December 2023 (123 g). Wind made 40.5% of the electricity generated, gas 29.4%, nuclear 12.8% and imports 9.2%; low-carbon sources together made 61.4%. The cleanest half hour was 32 g at 00:00 on Monday 23 December, and the dirtiest 303 g at 06:00 on Thursday 12 December. Sunday 22 December was both the cleanest day (51 g on average) and the windiest (64.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Mon 2 Dec | 161 | 53.7% | 34.6% | 1.5% | 35.5% | 35 |
| Tue 3 Dec | 217 | 38.3% | 18.4% | 1.3% | 49.9% | 48 |
| Wed 4 Dec | 202 | 46.0% | 29.0% | 0.8% | 48.0% | 48 |
| Thu 5 Dec | 96 | 70.1% | 52.5% | 0.5% | 18.8% | 48 |
| Fri 6 Dec | 119 | 64.8% | 44.7% | 1.1% | 25.0% | 48 |
| Sat 7 Dec | 76 | 74.2% | 55.8% | 0.3% | 15.6% | 48 |
| Sun 8 Dec | 67 | 76.3% | 57.8% | 0.8% | 13.7% | 48 |
| Mon 9 Dec | 133 | 56.4% | 37.1% | 0.8% | 29.5% | 48 |
| Tue 10 Dec | 197 | 43.3% | 24.6% | 0.3% | 46.3% | 48 |
| Wed 11 Dec | 264 | 28.0% | 9.0% | 0.2% | 63.5% | 48 |
| Thu 12 Dec | 278 | 26.1% | 5.6% | 0.3% | 67.0% | 48 |
| Fri 13 Dec | 271 | 29.6% | 9.0% | 0.3% | 65.5% | 48 |
| Sat 14 Dec | 139 | 60.5% | 39.2% | 1.8% | 32.8% | 48 |
| Sun 15 Dec | 61 | 80.6% | 62.2% | 0.8% | 12.8% | 48 |
| Mon 16 Dec | 81 | 76.1% | 57.2% | 0.8% | 18.5% | 48 |
| Tue 17 Dec | 113 | 67.8% | 47.6% | 0.3% | 26.3% | 48 |
| Wed 18 Dec | 81 | 72.4% | 52.6% | 0.7% | 17.3% | 48 |
| Thu 19 Dec | 66 | 74.4% | 53.7% | 1.7% | 13.4% | 48 |
| Fri 20 Dec | 72 | 72.9% | 52.2% | 0.7% | 14.8% | 48 |
| Sat 21 Dec | 59 | 81.4% | 62.8% | 0.7% | 12.6% | 48 |
| Sun 22 Dec | 51 | 83.7% | 64.8% | 1.5% | 10.6% | 48 |
| Mon 23 Dec | 102 | 64.8% | 43.8% | 0.6% | 23.2% | 48 |
| Tue 24 Dec | 86 | 70.5% | 47.5% | 0.9% | 18.3% | 48 |
| Wed 25 Dec | 99 | 66.6% | 39.5% | 1.0% | 21.4% | 48 |
| Thu 26 Dec | 162 | 43.7% | 14.9% | 0.9% | 39.7% | 48 |
| Fri 27 Dec | 209 | 34.5% | 9.3% | 0.5% | 53.1% | 48 |
| Sat 28 Dec | 174 | 48.4% | 22.2% | 0.5% | 42.2% | 48 |
| Sun 29 Dec | 91 | 73.0% | 47.9% | 1.0% | 21.0% | 48 |
| Mon 30 Dec | 71 | 79.0% | 55.1% | 1.6% | 14.5% | 48 |
| Tue 31 Dec | 61 | 81.9% | 61.7% | 0.7% | 13.0% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in December 2024, with December 2023 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 225 hours, 32%
- Low (70–139 g): 210 hours, 29%
- Moderate (140–219 g): 163 hours, 23%
- High (220–299 g): 115 hours, 16%
- Very high (300 g or more): 1 hours, 0%
Records in December 2024
- Cleanest half hour
- 32 g 00:00 on Monday 23 December
- Dirtiest half hour
- 303 g 06:00 on Thursday 12 December
- Most wind
- 72.7% 00:00 on Monday 23 December
- Most solar
- 10.4% 11:30 on Saturday 14 December
- Most low-carbon
- 91.5% 00:00 on Monday 23 December
- Least gas
- 5.5% 23:30 on Thursday 19 December
- Cleanest day
- 51 g Sunday 22 December
- Dirtiest day
- 278 g Thursday 12 December
- Windiest day
- 64.8% wind Sunday 22 December
- Sunniest day
- 1.8% solar Saturday 14 December
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.