In February 2021, Britain's electricity averaged 179 gCO₂/kWh, in the moderate band (140–219 g). That is 18% cleaner than January 2021 (219 g), and 2% dirtier than February 2020 (176 g). Gas made 35.1% of the electricity generated, wind 27.6%, nuclear 15.5% and imports 8.0%; low-carbon sources together made 54.3%. The cleanest half hour was 70 g at 02:00 on Thursday 25 February, and the dirtiest 297 g at 19:30 on Wednesday 10 February. The cleanest day was Saturday 20 February (108 g on average); the windiest was Saturday 13 February (42.3% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Mon 1 Feb | 258 | 36.0% | 11.3% | 0.9% | 50.2% | 48 |
| Tue 2 Feb | 167 | 54.7% | 32.9% | 1.1% | 33.7% | 48 |
| Wed 3 Feb | 194 | 52.3% | 27.3% | 1.1% | 34.2% | 48 |
| Thu 4 Feb | 188 | 50.1% | 25.1% | 0.8% | 39.3% | 48 |
| Fri 5 Feb | 205 | 48.3% | 21.7% | 1.8% | 39.9% | 48 |
| Sat 6 Feb | 156 | 56.8% | 33.1% | 1.5% | 32.6% | 48 |
| Sun 7 Feb | 123 | 66.2% | 42.0% | 0.9% | 24.3% | 48 |
| Mon 8 Feb | 168 | 56.0% | 32.4% | 1.1% | 34.6% | 48 |
| Tue 9 Feb | 222 | 45.8% | 22.7% | 1.4% | 42.1% | 48 |
| Wed 10 Feb | 260 | 41.1% | 15.9% | 2.2% | 45.7% | 48 |
| Thu 11 Feb | 248 | 41.0% | 16.5% | 2.2% | 46.8% | 48 |
| Fri 12 Feb | 169 | 60.1% | 34.9% | 2.4% | 31.5% | 48 |
| Sat 13 Feb | 128 | 68.1% | 42.3% | 2.1% | 23.0% | 48 |
| Sun 14 Feb | 130 | 67.7% | 42.3% | 0.6% | 21.9% | 48 |
| Mon 15 Feb | 175 | 56.5% | 28.1% | 1.8% | 32.5% | 48 |
| Tue 16 Feb | 166 | 61.2% | 33.6% | 1.2% | 29.4% | 48 |
| Wed 17 Feb | 158 | 64.6% | 36.5% | 1.6% | 24.9% | 48 |
| Thu 18 Feb | 155 | 65.8% | 36.7% | 2.4% | 25.3% | 48 |
| Fri 19 Feb | 139 | 63.9% | 36.8% | 0.8% | 25.0% | 48 |
| Sat 20 Feb | 108 | 68.8% | 41.8% | 1.8% | 22.1% | 48 |
| Sun 21 Feb | 168 | 54.9% | 26.0% | 1.9% | 36.5% | 48 |
| Mon 22 Feb | 216 | 43.9% | 15.1% | 2.0% | 43.5% | 48 |
| Tue 23 Feb | 129 | 64.6% | 33.5% | 2.8% | 26.2% | 48 |
| Wed 24 Feb | 122 | 66.2% | 36.1% | 2.0% | 26.7% | 48 |
| Thu 25 Feb | 175 | 54.7% | 25.1% | 3.2% | 34.8% | 48 |
| Fri 26 Feb | 205 | 43.1% | 13.0% | 5.1% | 47.2% | 48 |
| Sat 27 Feb | 239 | 37.5% | 6.3% | 5.4% | 51.6% | 48 |
| Sun 28 Feb | 247 | 31.4% | 4.2% | 5.4% | 57.6% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in February 2021, with February 2020 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 182 hours, 27%
- Moderate (140–219 g): 329 hours, 49%
- High (220–299 g): 162 hours, 24%
Records in February 2021
- Cleanest half hour
- 70 g 02:00 on Thursday 25 February
- Dirtiest half hour
- 297 g 19:30 on Wednesday 10 February
- Most wind
- 52.8% 04:30 on Sunday 7 February
- Most solar
- 21.1% 12:30 on Sunday 28 February
- Most low-carbon
- 79.9% 04:30 on Sunday 7 February
- Least gas
- 12.7% 02:00 on Thursday 25 February
- Cleanest day
- 108 g Saturday 20 February
- Dirtiest day
- 260 g Wednesday 10 February
- Windiest day
- 42.3% wind Saturday 13 February
- Sunniest day
- 5.4% solar Saturday 27 February
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 28 October 2026.