In August 2019, Britain's electricity averaged 182 gCO₂/kWh, in the moderate band (140–219 g). That is 18% cleaner than July 2019 (222 g). Gas made 35.0% of the electricity generated, nuclear 21.5%, wind 20.3% and imports 7.1%; low-carbon sources together made 56.7%. The cleanest half hour was 48 g at 16:00 on Thursday 22 August, and the dirtiest 293 g at 21:00 on Friday 2 August. The cleanest day was Saturday 10 August (91 g on average); the windiest was Saturday 17 August (40.4% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Thu 1 Aug | 233 | 44.2% | 9.1% | 5.4% | 48.5% | 48 |
| Fri 2 Aug | 254 | 41.2% | 5.4% | 6.1% | 52.1% | 48 |
| Sat 3 Aug | 241 | 40.4% | 4.3% | 6.5% | 49.2% | 48 |
| Sun 4 Aug | 216 | 46.0% | 10.5% | 5.7% | 43.3% | 48 |
| Mon 5 Aug | 180 | 54.7% | 18.3% | 6.6% | 35.1% | 48 |
| Tue 6 Aug | 174 | 58.0% | 19.0% | 5.9% | 31.6% | 48 |
| Wed 7 Aug | 160 | 61.5% | 21.9% | 6.1% | 28.8% | 48 |
| Thu 8 Aug | 216 | 49.8% | 11.6% | 6.1% | 41.8% | 48 |
| Fri 9 Aug | 124 | 70.0% | 34.3% | 5.1% | 23.3% | 48 |
| Sat 10 Aug | 91 | 75.6% | 34.0% | 5.5% | 16.9% | 48 |
| Sun 11 Aug | 114 | 71.8% | 31.6% | 6.2% | 21.8% | 48 |
| Mon 12 Aug | 226 | 45.9% | 12.1% | 5.5% | 44.3% | 48 |
| Tue 13 Aug | 232 | 44.6% | 9.4% | 6.9% | 44.1% | 48 |
| Wed 14 Aug | 232 | 44.2% | 14.3% | 1.7% | 44.9% | 48 |
| Thu 15 Aug | 148 | 63.9% | 27.5% | 6.6% | 24.9% | 48 |
| Fri 16 Aug | 148 | 63.0% | 33.0% | 1.5% | 30.0% | 48 |
| Sat 17 Aug | 116 | 73.6% | 40.4% | 6.8% | 21.3% | 48 |
| Sun 18 Aug | 117 | 74.4% | 39.2% | 7.6% | 20.5% | 48 |
| Mon 19 Aug | 147 | 65.4% | 30.7% | 6.5% | 26.4% | 48 |
| Tue 20 Aug | 207 | 50.0% | 13.8% | 6.5% | 40.2% | 48 |
| Wed 21 Aug | 173 | 56.0% | 20.4% | 6.2% | 32.8% | 48 |
| Thu 22 Aug | 136 | 64.7% | 31.3% | 5.8% | 25.5% | 48 |
| Fri 23 Aug | 169 | 59.4% | 21.1% | 7.5% | 30.0% | 48 |
| Sat 24 Aug | 196 | 52.3% | 12.8% | 8.6% | 38.5% | 48 |
| Sun 25 Aug | 218 | 45.4% | 7.3% | 8.5% | 43.9% | 48 |
| Mon 26 Aug | 230 | 46.5% | 8.3% | 7.4% | 48.0% | 48 |
| Tue 27 Aug | 263 | 41.3% | 6.3% | 5.2% | 51.8% | 48 |
| Wed 28 Aug | 237 | 47.7% | 14.7% | 3.7% | 47.1% | 48 |
| Thu 29 Aug | 174 | 62.4% | 25.2% | 6.2% | 32.5% | 48 |
| Fri 30 Aug | 137 | 70.5% | 32.2% | 5.7% | 23.7% | 48 |
| Sat 31 Aug | 117 | 72.2% | 28.4% | 6.3% | 22.4% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in August 2019, with July 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 1 hours, 0%
- Low (70–139 g): 216 hours, 29%
- Moderate (140–219 g): 286 hours, 38%
- High (220–299 g): 242 hours, 33%
Records in August 2019
- Cleanest half hour
- 48 g 16:00 on Thursday 22 August
- Dirtiest half hour
- 293 g 21:00 on Friday 2 August
- Most wind
- 75.5% 16:00 on Thursday 22 August
- Most solar
- 26.6% 12:30 on Saturday 24 August
- Most low-carbon
- 100.0% 16:00 on Thursday 22 August
- Least gas
- 0.0% 16:00 on Thursday 22 August
- Cleanest day
- 91 g Saturday 10 August
- Dirtiest day
- 263 g Tuesday 27 August
- Windiest day
- 40.4% wind Saturday 17 August
- Sunniest day
- 8.6% solar Saturday 24 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 31 October 2026.