In June 2021, Britain's electricity averaged 171 gCO₂/kWh, in the moderate band (140–219 g). That is 4% cleaner than May 2021 (178 g), and about the same as June 2020 (172 g). Gas made 36.0% of the electricity generated, nuclear 19.0%, wind 16.6% and imports 12.8%; low-carbon sources together made 50.8%. The cleanest half hour was 78 g at 03:30 on Monday 14 June, and the dirtiest 262 g at 21:30 on Wednesday 23 June. Friday 11 June was both the cleanest day (113 g on average) and the windiest (32.5% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Tue 1 Jun | 145 | 57.9% | 20.8% | 9.7% | 31.5% | 48 |
| Wed 2 Jun | 134 | 62.9% | 29.4% | 7.6% | 27.8% | 48 |
| Thu 3 Jun | 158 | 51.8% | 18.9% | 5.9% | 36.8% | 48 |
| Fri 4 Jun | 171 | 47.8% | 12.4% | 6.4% | 39.8% | 48 |
| Sat 5 Jun | 164 | 50.1% | 8.3% | 8.9% | 37.5% | 48 |
| Sun 6 Jun | 184 | 44.0% | 4.4% | 6.9% | 42.3% | 48 |
| Mon 7 Jun | 188 | 45.2% | 8.5% | 6.9% | 43.3% | 48 |
| Tue 8 Jun | 162 | 53.5% | 14.2% | 9.0% | 35.2% | 48 |
| Wed 9 Jun | 142 | 59.0% | 21.5% | 7.1% | 29.9% | 48 |
| Thu 10 Jun | 135 | 60.8% | 26.6% | 4.6% | 27.6% | 48 |
| Fri 11 Jun | 113 | 66.4% | 32.5% | 5.1% | 23.6% | 48 |
| Sat 12 Jun | 122 | 62.6% | 21.1% | 9.7% | 26.4% | 48 |
| Sun 13 Jun | 124 | 61.8% | 19.7% | 9.4% | 25.7% | 48 |
| Mon 14 Jun | 125 | 62.5% | 26.1% | 6.9% | 26.2% | 48 |
| Tue 15 Jun | 167 | 53.9% | 15.2% | 9.0% | 35.3% | 48 |
| Wed 16 Jun | 156 | 54.3% | 18.9% | 7.4% | 34.1% | 48 |
| Thu 17 Jun | 210 | 42.4% | 8.8% | 4.7% | 44.7% | 48 |
| Fri 18 Jun | 176 | 50.7% | 19.0% | 3.1% | 36.7% | 48 |
| Sat 19 Jun | 173 | 49.0% | 14.4% | 4.3% | 37.5% | 48 |
| Sun 20 Jun | 174 | 46.9% | 13.5% | 4.0% | 37.7% | 48 |
| Mon 21 Jun | 165 | 49.5% | 22.2% | 3.2% | 33.3% | 48 |
| Tue 22 Jun | 184 | 48.6% | 18.1% | 6.5% | 36.0% | 48 |
| Wed 23 Jun | 224 | 39.7% | 6.4% | 7.7% | 44.9% | 48 |
| Thu 24 Jun | 208 | 42.4% | 12.0% | 4.9% | 43.5% | 48 |
| Fri 25 Jun | 177 | 52.8% | 23.1% | 4.5% | 32.0% | 48 |
| Sat 26 Jun | 199 | 42.8% | 10.3% | 7.1% | 39.6% | 48 |
| Sun 27 Jun | 191 | 44.8% | 16.6% | 3.7% | 37.7% | 48 |
| Mon 28 Jun | 230 | 37.3% | 9.5% | 3.6% | 45.8% | 48 |
| Tue 29 Jun | 216 | 39.0% | 10.8% | 4.4% | 45.9% | 48 |
| Wed 30 Jun | 203 | 42.4% | 13.5% | 5.1% | 41.9% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in June 2021, with June 2020 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 158 hours, 22%
- Moderate (140–219 g): 502 hours, 70%
- High (220–299 g): 61 hours, 8%
Records in June 2021
- Cleanest half hour
- 78 g 03:30 on Monday 14 June
- Dirtiest half hour
- 262 g 21:30 on Wednesday 23 June
- Most wind
- 41.2% 02:30 on Friday 11 June
- Most solar
- 26.9% 14:00 on Saturday 12 June
- Most low-carbon
- 78.4% 04:30 on Monday 14 June
- Least gas
- 15.2% 14:00 on Sunday 13 June
- Cleanest day
- 113 g Friday 11 June
- Dirtiest day
- 230 g Monday 28 June
- Windiest day
- 32.5% wind Friday 11 June
- Sunniest day
- 9.7% solar Tuesday 1 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 27 October 2026.