In October 2019, Britain's electricity averaged 202 gCO₂/kWh, in the moderate band (140–219 g). That is 13% dirtier than September 2019 (178 g). Gas made 39.7% of the electricity generated, nuclear 21.9%, wind 21.4% and imports 5.7%; low-carbon sources together made 53.0%. The cleanest half hour was 75 g at 02:00 on Thursday 10 October, and the dirtiest 311 g at 07:00 on Monday 28 October. The cleanest day was Sunday 6 October (127 g on average); the windiest was Thursday 10 October (35.6% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Tue 1 Oct | 194 | 56.9% | 25.0% | 2.4% | 37.8% | 48 |
| Wed 2 Oct | 207 | 53.7% | 20.3% | 5.0% | 40.5% | 48 |
| Thu 3 Oct | 225 | 48.2% | 17.6% | 1.9% | 44.6% | 48 |
| Fri 4 Oct | 192 | 55.6% | 23.3% | 1.9% | 36.2% | 48 |
| Sat 5 Oct | 183 | 54.3% | 19.2% | 2.5% | 35.2% | 48 |
| Sun 6 Oct | 127 | 68.3% | 32.5% | 3.6% | 24.6% | 48 |
| Mon 7 Oct | 185 | 59.4% | 27.9% | 1.1% | 35.6% | 48 |
| Tue 8 Oct | 141 | 68.7% | 34.6% | 3.2% | 26.7% | 48 |
| Wed 9 Oct | 136 | 68.5% | 34.6% | 3.2% | 25.5% | 48 |
| Thu 10 Oct | 138 | 68.4% | 35.6% | 2.6% | 24.0% | 48 |
| Fri 11 Oct | 140 | 66.7% | 35.2% | 1.3% | 24.6% | 48 |
| Sat 12 Oct | 191 | 51.0% | 17.1% | 1.9% | 39.2% | 48 |
| Sun 13 Oct | 218 | 44.5% | 12.7% | 1.4% | 45.9% | 48 |
| Mon 14 Oct | 253 | 39.5% | 10.6% | 0.9% | 51.0% | 48 |
| Tue 15 Oct | 260 | 41.3% | 11.7% | 2.0% | 49.3% | 48 |
| Wed 16 Oct | 218 | 49.2% | 19.3% | 2.6% | 40.2% | 48 |
| Thu 17 Oct | 249 | 44.1% | 15.2% | 2.6% | 48.5% | 48 |
| Fri 18 Oct | 228 | 48.4% | 19.9% | 2.4% | 43.4% | 48 |
| Sat 19 Oct | 162 | 58.1% | 25.3% | 3.2% | 33.0% | 48 |
| Sun 20 Oct | 160 | 57.6% | 23.8% | 2.5% | 33.0% | 48 |
| Mon 21 Oct | 235 | 48.5% | 17.8% | 1.4% | 47.9% | 48 |
| Tue 22 Oct | 232 | 48.9% | 17.6% | 2.8% | 48.5% | 48 |
| Wed 23 Oct | 228 | 47.7% | 16.9% | 2.1% | 46.5% | 48 |
| Thu 24 Oct | 217 | 48.0% | 17.1% | 1.2% | 43.9% | 48 |
| Fri 25 Oct | 198 | 52.0% | 23.1% | 0.6% | 38.8% | 48 |
| Sat 26 Oct | 173 | 57.2% | 27.2% | 0.7% | 33.5% | 48 |
| Sun 27 Oct | 153 | 62.6% | 25.6% | 4.2% | 29.5% | 50 |
| Mon 28 Oct | 271 | 38.6% | 9.3% | 2.4% | 53.4% | 48 |
| Tue 29 Oct | 255 | 42.6% | 12.8% | 1.9% | 50.6% | 48 |
| Wed 30 Oct | 249 | 46.1% | 16.0% | 2.0% | 50.5% | 48 |
| Thu 31 Oct | 233 | 47.2% | 17.2% | 1.6% | 48.9% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in October 2019, with September 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 121 hours, 16%
- Moderate (140–219 g): 304 hours, 41%
- High (220–299 g): 320 hours, 43%
- Very high (300 g or more): 2 hours, 0%
Records in October 2019
- Cleanest half hour
- 75 g 02:00 on Thursday 10 October
- Dirtiest half hour
- 311 g 07:00 on Monday 28 October
- Most wind
- 47.8% 03:30 on Friday 11 October
- Most solar
- 19.7% 11:00 on Sunday 27 October
- Most low-carbon
- 83.8% 03:30 on Thursday 10 October
- Least gas
- 12.2% 01:00 on Friday 11 October
- Cleanest day
- 127 g Sunday 6 October
- Dirtiest day
- 271 g Monday 28 October
- Windiest day
- 35.6% wind Thursday 10 October
- Sunniest day
- 5.0% solar Wednesday 2 October
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 30 October 2026.