In May 2024, Britain's electricity averaged 124 gCO₂/kWh, in the low band (70–139 g). That is 33% dirtier than April 2024 (93 g), and 16% cleaner than May 2023 (148 g). Gas made 27.1% of the electricity generated, wind 20.3%, nuclear 18.9% and imports 16.5%; low-carbon sources together made 56.0%. The cleanest half hour was 35 g at 13:00 on Sunday 12 May, and the dirtiest 221 g at 20:30 on Friday 17 May. The cleanest day was Thursday 30 May (54 g on average); the windiest was Thursday 23 May (42.7% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 May | 130 | 56.7% | 17.5% | 6.3% | 26.4% | 48 |
| Thu 2 May | 73 | 70.1% | 36.3% | 5.2% | 13.2% | 48 |
| Fri 3 May | 115 | 59.6% | 26.5% | 3.6% | 23.2% | 48 |
| Sat 4 May | 131 | 55.0% | 16.2% | 8.4% | 27.6% | 48 |
| Sun 5 May | 162 | 45.5% | 6.1% | 7.9% | 34.7% | 48 |
| Mon 6 May | 161 | 46.7% | 7.6% | 6.2% | 35.9% | 48 |
| Tue 7 May | 167 | 46.7% | 8.1% | 8.1% | 36.9% | 48 |
| Wed 8 May | 150 | 51.6% | 11.7% | 9.1% | 34.0% | 48 |
| Thu 9 May | 140 | 52.4% | 11.5% | 10.9% | 30.6% | 48 |
| Fri 10 May | 155 | 47.8% | 6.8% | 10.5% | 34.9% | 48 |
| Sat 11 May | 99 | 60.4% | 18.5% | 11.8% | 22.6% | 48 |
| Sun 12 May | 76 | 71.4% | 34.6% | 10.7% | 16.0% | 48 |
| Mon 13 May | 110 | 65.5% | 28.4% | 6.2% | 22.5% | 48 |
| Tue 14 May | 127 | 60.4% | 30.1% | 4.9% | 29.1% | 48 |
| Wed 15 May | 165 | 46.6% | 11.3% | 7.6% | 39.0% | 48 |
| Thu 16 May | 182 | 42.2% | 10.3% | 5.1% | 42.0% | 48 |
| Fri 17 May | 171 | 42.4% | 8.0% | 9.3% | 40.6% | 48 |
| Sat 18 May | 145 | 47.6% | 11.6% | 8.7% | 32.5% | 48 |
| Sun 19 May | 111 | 55.9% | 15.1% | 12.6% | 22.6% | 48 |
| Mon 20 May | 144 | 49.8% | 14.9% | 9.9% | 31.2% | 48 |
| Tue 21 May | 178 | 40.0% | 8.3% | 5.9% | 41.7% | 48 |
| Wed 22 May | 113 | 58.0% | 30.8% | 3.2% | 24.8% | 48 |
| Thu 23 May | 78 | 70.4% | 42.7% | 5.3% | 17.3% | 48 |
| Fri 24 May | 181 | 39.2% | 8.2% | 6.4% | 43.4% | 48 |
| Sat 25 May | 108 | 55.8% | 17.7% | 10.5% | 22.1% | 48 |
| Sun 26 May | 85 | 61.6% | 25.3% | 8.1% | 15.1% | 48 |
| Mon 27 May | 90 | 62.7% | 24.0% | 10.0% | 17.1% | 48 |
| Tue 28 May | 100 | 60.4% | 28.8% | 3.9% | 20.8% | 48 |
| Wed 29 May | 98 | 67.7% | 30.9% | 10.3% | 17.0% | 48 |
| Thu 30 May | 54 | 72.2% | 39.9% | 7.2% | 13.0% | 48 |
| Fri 31 May | 56 | 73.5% | 41.6% | 6.5% | 11.1% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in May 2024, with May 2023 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 124 hours, 17%
- Low (70–139 g): 319 hours, 43%
- Moderate (140–219 g): 302 hours, 41%
- High (220–299 g): 1 hours, 0%
Records in May 2024
- Cleanest half hour
- 35 g 13:00 on Sunday 12 May
- Dirtiest half hour
- 221 g 20:30 on Friday 17 May
- Most wind
- 61.5% 02:30 on Thursday 23 May
- Most solar
- 36.0% 13:00 on Sunday 19 May
- Most low-carbon
- 84.5% 03:30 on Thursday 23 May
- Least gas
- 6.0% 10:00 on Thursday 23 May
- Cleanest day
- 54 g Thursday 30 May
- Dirtiest day
- 182 g Thursday 16 May
- Windiest day
- 42.7% wind Thursday 23 May
- Sunniest day
- 12.6% solar Sunday 19 May
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 22 October 2026.