In August 2023, Britain's electricity averaged 161 gCO₂/kWh, in the moderate band (140–219 g). That is 13% dirtier than July 2023 (143 g), and 27% cleaner than August 2022 (221 g). Gas made 36.2% of the electricity generated, wind 25.1%, nuclear 15.7% and imports 11.1%; low-carbon sources together made 52.3%. The cleanest half hour was 40 g at 13:30 on Saturday 19 August, and the dirtiest 283 g at 22:30 on Tuesday 15 August. Saturday 19 August was both the cleanest day (90 g on average) and the windiest (51.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Tue 1 Aug | 147 | 56.3% | 30.7% | 5.8% | 32.3% | 48 |
| Wed 2 Aug | 107 | 63.5% | 40.3% | 4.5% | 21.4% | 48 |
| Thu 3 Aug | 116 | 60.8% | 39.0% | 6.0% | 25.0% | 48 |
| Fri 4 Aug | 184 | 44.4% | 20.0% | 5.5% | 41.8% | 48 |
| Sat 5 Aug | 172 | 42.8% | 19.5% | 3.9% | 39.3% | 48 |
| Sun 6 Aug | 101 | 60.1% | 34.9% | 8.4% | 20.2% | 48 |
| Mon 7 Aug | 145 | 50.0% | 23.0% | 7.7% | 29.2% | 48 |
| Tue 8 Aug | 149 | 52.8% | 28.3% | 4.5% | 32.3% | 48 |
| Wed 9 Aug | 188 | 44.4% | 14.7% | 7.6% | 41.5% | 48 |
| Thu 10 Aug | 201 | 42.1% | 12.7% | 7.6% | 46.7% | 48 |
| Fri 11 Aug | 116 | 66.9% | 38.4% | 7.7% | 23.3% | 48 |
| Sat 12 Aug | 100 | 69.5% | 44.0% | 6.0% | 19.9% | 48 |
| Sun 13 Aug | 114 | 62.9% | 36.6% | 6.0% | 23.8% | 48 |
| Mon 14 Aug | 164 | 50.2% | 24.9% | 4.1% | 38.0% | 48 |
| Tue 15 Aug | 195 | 41.9% | 13.4% | 7.1% | 44.1% | 48 |
| Wed 16 Aug | 232 | 34.2% | 5.4% | 7.6% | 53.7% | 48 |
| Thu 17 Aug | 161 | 55.7% | 29.9% | 6.1% | 38.2% | 48 |
| Fri 18 Aug | 136 | 63.2% | 41.0% | 2.9% | 29.5% | 48 |
| Sat 19 Aug | 90 | 76.3% | 51.8% | 6.8% | 18.8% | 48 |
| Sun 20 Aug | 127 | 59.3% | 29.5% | 8.5% | 27.8% | 48 |
| Mon 21 Aug | 149 | 58.8% | 34.0% | 5.9% | 34.5% | 48 |
| Tue 22 Aug | 175 | 54.2% | 29.4% | 6.4% | 38.5% | 48 |
| Wed 23 Aug | 241 | 36.8% | 10.7% | 6.3% | 51.6% | 48 |
| Thu 24 Aug | 233 | 40.1% | 13.2% | 5.1% | 52.8% | 48 |
| Fri 25 Aug | 218 | 41.6% | 12.3% | 5.6% | 52.8% | 48 |
| Sat 26 Aug | 176 | 47.2% | 11.3% | 7.0% | 40.6% | 48 |
| Sun 27 Aug | 134 | 54.6% | 18.9% | 6.0% | 29.9% | 48 |
| Mon 28 Aug | 171 | 50.2% | 16.4% | 5.5% | 40.8% | 48 |
| Tue 29 Aug | 175 | 51.1% | 22.1% | 3.9% | 42.6% | 48 |
| Wed 30 Aug | 167 | 52.9% | 22.0% | 6.1% | 40.3% | 48 |
| Thu 31 Aug | 216 | 37.8% | 8.7% | 3.9% | 51.9% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in August 2023, with August 2022 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 18 hours, 2%
- Low (70–139 g): 249 hours, 33%
- Moderate (140–219 g): 367 hours, 49%
- High (220–299 g): 111 hours, 15%
Records in August 2023
- Cleanest half hour
- 40 g 13:30 on Saturday 19 August
- Dirtiest half hour
- 283 g 22:30 on Tuesday 15 August
- Most wind
- 58.0% 03:00 on Saturday 19 August
- Most solar
- 24.7% 12:30 on Sunday 20 August
- Most low-carbon
- 90.0% 13:30 on Saturday 19 August
- Least gas
- 9.1% 12:00 on Friday 11 August
- Cleanest day
- 90 g Saturday 19 August
- Dirtiest day
- 241 g Wednesday 23 August
- Windiest day
- 51.8% wind Saturday 19 August
- Sunniest day
- 8.5% solar Sunday 20 August
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 23 October 2026.