In July 2019, Britain's electricity averaged 222 gCO₂/kWh, in the high band (220–299 g). That is 3% dirtier than June 2019 (216 g). Gas made 45.3% of the electricity generated, nuclear 18.7%, wind 13.5% and imports 7.8%; low-carbon sources together made 46.3%. The cleanest half hour was 91 g at 14:00 on Saturday 20 July, and the dirtiest 314 g at 04:00 on Thursday 25 July. The cleanest day was Saturday 20 July (146 g on average); the windiest was Monday 1 July (30.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Mon 1 Jul | 148 | 63.2% | 30.8% | 6.7% | 29.1% | 48 |
| Tue 2 Jul | 227 | 44.8% | 13.6% | 6.8% | 45.1% | 48 |
| Wed 3 Jul | 248 | 40.8% | 9.4% | 7.8% | 50.2% | 48 |
| Thu 4 Jul | 219 | 46.2% | 15.8% | 8.3% | 44.0% | 48 |
| Fri 5 Jul | 226 | 44.4% | 14.0% | 7.5% | 45.5% | 48 |
| Sat 6 Jul | 226 | 44.9% | 13.5% | 5.8% | 45.3% | 48 |
| Sun 7 Jul | 243 | 41.5% | 7.9% | 7.5% | 47.6% | 48 |
| Mon 8 Jul | 274 | 35.0% | 4.9% | 6.4% | 55.1% | 48 |
| Tue 9 Jul | 270 | 34.2% | 5.3% | 4.1% | 56.0% | 48 |
| Wed 10 Jul | 259 | 35.4% | 6.4% | 5.8% | 54.8% | 48 |
| Thu 11 Jul | 267 | 35.7% | 6.5% | 5.7% | 56.5% | 48 |
| Fri 12 Jul | 222 | 44.2% | 11.4% | 7.0% | 44.2% | 48 |
| Sat 13 Jul | 213 | 45.4% | 11.6% | 5.7% | 43.5% | 48 |
| Sun 14 Jul | 226 | 44.1% | 8.9% | 6.5% | 44.5% | 48 |
| Mon 15 Jul | 258 | 36.8% | 4.4% | 6.7% | 53.0% | 48 |
| Tue 16 Jul | 258 | 37.3% | 3.4% | 7.1% | 52.4% | 48 |
| Wed 17 Jul | 221 | 46.0% | 12.6% | 5.8% | 47.2% | 48 |
| Thu 18 Jul | 220 | 47.4% | 13.8% | 5.8% | 45.9% | 48 |
| Fri 19 Jul | 224 | 45.9% | 14.0% | 2.5% | 48.3% | 48 |
| Sat 20 Jul | 146 | 62.8% | 23.3% | 7.3% | 27.1% | 48 |
| Sun 21 Jul | 155 | 61.9% | 21.3% | 7.1% | 27.2% | 48 |
| Mon 22 Jul | 157 | 64.3% | 29.9% | 6.5% | 30.3% | 48 |
| Tue 23 Jul | 214 | 50.0% | 15.8% | 7.8% | 45.5% | 48 |
| Wed 24 Jul | 240 | 47.2% | 15.4% | 6.7% | 49.6% | 48 |
| Thu 25 Jul | 246 | 47.2% | 15.9% | 6.6% | 50.2% | 48 |
| Fri 26 Jul | 246 | 43.3% | 13.1% | 4.3% | 52.5% | 48 |
| Sat 27 Jul | 232 | 43.8% | 12.3% | 3.4% | 46.1% | 48 |
| Sun 28 Jul | 191 | 52.7% | 18.4% | 4.8% | 38.4% | 48 |
| Mon 29 Jul | 236 | 44.1% | 8.7% | 7.0% | 49.6% | 48 |
| Tue 30 Jul | 206 | 49.4% | 15.8% | 4.2% | 43.5% | 48 |
| Wed 31 Jul | 177 | 56.6% | 20.6% | 5.1% | 37.7% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in July 2019, with June 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 42 hours, 6%
- Moderate (140–219 g): 260 hours, 35%
- High (220–299 g): 435 hours, 58%
- Very high (300 g or more): 8 hours, 1%
Records in July 2019
- Cleanest half hour
- 91 g 14:00 on Saturday 20 July
- Dirtiest half hour
- 314 g 04:00 on Thursday 25 July
- Most wind
- 45.4% 01:00 on Monday 1 July
- Most solar
- 24.4% 13:00 on Thursday 4 July
- Most low-carbon
- 77.9% 01:30 on Monday 22 July
- Least gas
- 16.6% 14:00 on Saturday 20 July
- Cleanest day
- 146 g Saturday 20 July
- Dirtiest day
- 274 g Monday 8 July
- Windiest day
- 30.8% wind Monday 1 July
- Sunniest day
- 8.3% solar Thursday 4 July
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.