In April 2023, Britain's electricity averaged 161 gCO₂/kWh, in the moderate band (140–219 g). That is 2% dirtier than March 2023 (158 g), and 11% cleaner than April 2022 (181 g). Gas made 35.7% of the electricity generated, wind 25.4%, nuclear 14.7% and imports 11.5%; low-carbon sources together made 52.8%. The cleanest half hour was 32 g at 14:30 on Monday 10 April, and the dirtiest 285 g at 05:00 on Wednesday 26 April. Monday 10 April was both the cleanest day (61 g on average) and the windiest (52.6% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Sat 1 Apr | 115 | 57.9% | 33.1% | 3.0% | 25.1% | 48 |
| Sun 2 Apr | 153 | 48.5% | 20.0% | 5.3% | 32.8% | 48 |
| Mon 3 Apr | 163 | 53.2% | 25.4% | 7.4% | 35.3% | 48 |
| Tue 4 Apr | 186 | 49.5% | 21.2% | 7.8% | 41.4% | 48 |
| Wed 5 Apr | 211 | 43.5% | 19.4% | 2.5% | 47.6% | 48 |
| Thu 6 Apr | 169 | 54.2% | 28.0% | 4.8% | 38.4% | 48 |
| Fri 7 Apr | 188 | 47.5% | 14.2% | 8.8% | 42.8% | 48 |
| Sat 8 Apr | 185 | 48.7% | 15.7% | 8.2% | 41.7% | 48 |
| Sun 9 Apr | 118 | 65.6% | 33.7% | 6.3% | 25.1% | 48 |
| Mon 10 Apr | 61 | 80.6% | 52.6% | 5.1% | 11.5% | 48 |
| Tue 11 Apr | 100 | 72.1% | 46.8% | 4.2% | 21.8% | 48 |
| Wed 12 Apr | 97 | 72.0% | 46.2% | 4.4% | 20.7% | 48 |
| Thu 13 Apr | 115 | 67.3% | 37.6% | 6.3% | 24.9% | 48 |
| Fri 14 Apr | 231 | 38.2% | 11.6% | 3.2% | 53.9% | 48 |
| Sat 15 Apr | 183 | 43.7% | 11.5% | 6.9% | 40.4% | 48 |
| Sun 16 Apr | 191 | 44.7% | 12.9% | 4.3% | 44.2% | 48 |
| Mon 17 Apr | 230 | 38.8% | 9.9% | 4.1% | 53.9% | 48 |
| Tue 18 Apr | 141 | 60.9% | 32.4% | 6.3% | 29.7% | 48 |
| Wed 19 Apr | 102 | 68.7% | 42.3% | 5.9% | 19.8% | 48 |
| Thu 20 Apr | 119 | 66.6% | 37.0% | 8.5% | 24.3% | 48 |
| Fri 21 Apr | 160 | 53.7% | 30.0% | 3.8% | 34.5% | 48 |
| Sat 22 Apr | 159 | 47.4% | 21.0% | 5.2% | 35.9% | 48 |
| Sun 23 Apr | 126 | 56.4% | 30.0% | 4.3% | 25.3% | 48 |
| Mon 24 Apr | 144 | 56.8% | 33.4% | 4.1% | 30.8% | 48 |
| Tue 25 Apr | 197 | 43.2% | 16.0% | 7.5% | 44.2% | 48 |
| Wed 26 Apr | 245 | 31.4% | 6.2% | 4.8% | 56.0% | 48 |
| Thu 27 Apr | 191 | 48.6% | 27.4% | 2.7% | 43.9% | 48 |
| Fri 28 Apr | 190 | 44.0% | 19.2% | 4.4% | 43.7% | 48 |
| Sat 29 Apr | 208 | 32.6% | 6.3% | 7.1% | 48.3% | 48 |
| Sun 30 Apr | 147 | 47.3% | 21.6% | 5.1% | 31.7% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in April 2023, with April 2022 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 31 hours, 4%
- Low (70–139 g): 221 hours, 31%
- Moderate (140–219 g): 361 hours, 50%
- High (220–299 g): 108 hours, 15%
Records in April 2023
- Cleanest half hour
- 32 g 14:30 on Monday 10 April
- Dirtiest half hour
- 285 g 05:00 on Wednesday 26 April
- Most wind
- 61.2% 23:00 on Monday 10 April
- Most solar
- 27.3% 13:00 on Friday 7 April
- Most low-carbon
- 88.1% 15:30 on Monday 10 April
- Least gas
- 6.3% 15:00 on Monday 10 April
- Cleanest day
- 61 g Monday 10 April
- Dirtiest day
- 245 g Wednesday 26 April
- Windiest day
- 52.6% wind Monday 10 April
- Sunniest day
- 8.8% solar Friday 7 April
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 24 October 2026.