In January 2020, Britain's electricity averaged 209 gCO₂/kWh, in the moderate band (140–219 g). That is 3% dirtier than December 2019 (203 g). Gas made 31.4% of the electricity generated, wind 26.3%, nuclear 20.1% and biomass 7.0%; low-carbon sources together made 56.9%. The cleanest half hour was 92 g at 23:00 on Wednesday 29 January, and the dirtiest 371 g at 06:30 on Tuesday 21 January. The cleanest day was Friday 31 January (141 g on average); the windiest was Saturday 11 January (38.9% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 Jan | 192 | – | – | – | – | 48 |
| Thu 2 Jan | 175 | – | – | – | – | 48 |
| Fri 3 Jan | 166 | 62.6% | 33.5% | 0.1% | 24.4% | 48 |
| Sat 4 Jan | 179 | 63.1% | 29.8% | 1.1% | 24.3% | 48 |
| Sun 5 Jan | 172 | 65.1% | 31.8% | 0.5% | 21.4% | 48 |
| Mon 6 Jan | 187 | 64.4% | 34.1% | 0.4% | 23.9% | 48 |
| Tue 7 Jan | 171 | 65.8% | 35.7% | 0.4% | 24.8% | 48 |
| Wed 8 Jan | 239 | 53.1% | 24.1% | 0.5% | 37.8% | 48 |
| Thu 9 Jan | 256 | 48.9% | 18.4% | 0.8% | 38.9% | 48 |
| Fri 10 Jan | 233 | 52.1% | 20.9% | 1.6% | 34.7% | 48 |
| Sat 11 Jan | 143 | 71.2% | 38.9% | 0.5% | 16.4% | 48 |
| Sun 12 Jan | 166 | 64.2% | 29.4% | 1.3% | 22.9% | 48 |
| Mon 13 Jan | 185 | 64.0% | 33.7% | 0.6% | 24.6% | 48 |
| Tue 14 Jan | 183 | 63.5% | 33.3% | 0.2% | 24.1% | 48 |
| Wed 15 Jan | 165 | 65.6% | 33.8% | 1.5% | 21.9% | 48 |
| Thu 16 Jan | 167 | 65.8% | 35.0% | 0.5% | 22.8% | 48 |
| Fri 17 Jan | 189 | 59.2% | 29.4% | 0.9% | 28.6% | 48 |
| Sat 18 Jan | 209 | 58.8% | 26.1% | 2.5% | 28.2% | 48 |
| Sun 19 Jan | 246 | 49.3% | 17.7% | 2.5% | 34.7% | 48 |
| Mon 20 Jan | 290 | 43.9% | 16.7% | 1.9% | 44.9% | 48 |
| Tue 21 Jan | 324 | 35.4% | 8.2% | 1.8% | 53.0% | 48 |
| Wed 22 Jan | 325 | 34.9% | 6.7% | 0.5% | 54.8% | 48 |
| Thu 23 Jan | 332 | 39.1% | 11.1% | 0.4% | 51.5% | 48 |
| Fri 24 Jan | 341 | 37.2% | 8.3% | 0.3% | 50.5% | 48 |
| Sat 25 Jan | 228 | 53.2% | 21.6% | 0.3% | 33.8% | 48 |
| Sun 26 Jan | 175 | 61.8% | 28.1% | 0.6% | 27.8% | 48 |
| Mon 27 Jan | 206 | 55.1% | 26.0% | 1.0% | 34.9% | 48 |
| Tue 28 Jan | 174 | 58.6% | 28.7% | 1.8% | 29.4% | 48 |
| Wed 29 Jan | 153 | 65.9% | 34.9% | 2.0% | 25.3% | 48 |
| Thu 30 Jan | 153 | 65.4% | 33.9% | 0.5% | 23.4% | 48 |
| Fri 31 Jan | 141 | 67.3% | 36.2% | 0.6% | 21.1% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in January 2020, with December 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 115 hours, 15%
- Moderate (140–219 g): 364 hours, 49%
- High (220–299 g): 152 hours, 20%
- Very high (300 g or more): 114 hours, 15%
Records in January 2020
- Cleanest half hour
- 92 g 23:00 on Wednesday 29 January
- Dirtiest half hour
- 371 g 06:30 on Tuesday 21 January
- Most wind
- 46.8% 22:30 on Tuesday 7 January
- Most solar
- 12.9% 11:30 on Saturday 18 January
- Most low-carbon
- 83.5% 03:30 on Wednesday 8 January
- Least gas
- 11.5% 10:30 on Saturday 11 January
- Cleanest day
- 141 g Friday 31 January
- Dirtiest day
- 341 g Friday 24 January
- Windiest day
- 38.9% wind Saturday 11 January
- Sunniest day
- 2.5% solar Saturday 18 January
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.