In April 2019, Britain's electricity averaged 212 gCO₂/kWh, in the moderate band (140–219 g). That is 8% dirtier than March 2019 (197 g). Gas made 41.7% of the electricity generated, nuclear 21.0%, wind 17.1% and imports 6.4%; low-carbon sources together made 50.5%. The cleanest half hour was 99 g at 03:00 on Saturday 27 April, and the dirtiest 309 g at 19:00 on Thursday 11 April. Saturday 27 April was both the cleanest day (134 g on average) and the windiest (30.4% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Mon 1 Apr | 214 | 50.8% | 16.9% | 6.0% | 40.8% | 48 |
| Tue 2 Apr | 262 | 40.4% | 9.9% | 4.1% | 50.7% | 48 |
| Wed 3 Apr | 238 | 46.2% | 15.4% | 3.5% | 46.1% | 48 |
| Thu 4 Apr | 211 | 51.6% | 21.9% | 2.8% | 41.0% | 48 |
| Fri 5 Apr | 190 | 57.1% | 25.0% | 3.6% | 35.9% | 48 |
| Sat 6 Apr | 232 | 44.3% | 12.1% | 4.2% | 48.1% | 48 |
| Sun 7 Apr | 219 | 47.8% | 16.2% | 3.3% | 44.7% | 48 |
| Mon 8 Apr | 245 | 46.2% | 14.4% | 3.7% | 45.7% | 48 |
| Tue 9 Apr | 227 | 49.7% | 18.8% | 3.1% | 43.1% | 48 |
| Wed 10 Apr | 247 | 43.6% | 12.0% | 6.3% | 48.7% | 48 |
| Thu 11 Apr | 274 | 39.0% | 6.9% | 6.7% | 52.9% | 48 |
| Fri 12 Apr | 253 | 41.1% | 13.0% | 4.5% | 50.9% | 48 |
| Sat 13 Apr | 181 | 55.1% | 24.6% | 6.7% | 37.0% | 48 |
| Sun 14 Apr | 165 | 59.6% | 29.1% | 4.8% | 32.4% | 48 |
| Mon 15 Apr | 163 | 63.6% | 29.5% | 6.5% | 26.9% | 48 |
| Tue 16 Apr | 220 | 50.3% | 17.7% | 3.2% | 42.4% | 48 |
| Wed 17 Apr | 239 | 46.7% | 12.8% | 6.0% | 44.1% | 48 |
| Thu 18 Apr | 208 | 53.5% | 17.1% | 6.7% | 38.6% | 48 |
| Fri 19 Apr | 205 | 51.1% | 14.3% | 9.2% | 43.0% | 48 |
| Sat 20 Apr | 205 | 52.1% | 8.4% | 9.6% | 40.4% | 48 |
| Sun 21 Apr | 198 | 53.2% | 11.5% | 8.8% | 40.0% | 48 |
| Mon 22 Apr | 165 | 60.1% | 21.1% | 8.7% | 34.1% | 48 |
| Tue 23 Apr | 195 | 56.7% | 21.6% | 5.3% | 35.5% | 48 |
| Wed 24 Apr | 206 | 52.1% | 21.3% | 3.8% | 40.4% | 48 |
| Thu 25 Apr | 200 | 50.5% | 19.8% | 5.2% | 42.7% | 48 |
| Fri 26 Apr | 165 | 59.0% | 27.0% | 4.8% | 33.1% | 48 |
| Sat 27 Apr | 134 | 65.6% | 30.4% | 5.2% | 26.3% | 48 |
| Sun 28 Apr | 201 | 50.7% | 15.1% | 5.1% | 42.5% | 48 |
| Mon 29 Apr | 263 | 37.4% | 5.3% | 4.6% | 52.8% | 48 |
| Tue 30 Apr | 249 | 40.5% | 5.3% | 6.0% | 50.8% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in April 2019, with March 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 52 hours, 7%
- Moderate (140–219 g): 332 hours, 46%
- High (220–299 g): 333 hours, 46%
- Very high (300 g or more): 4 hours, 1%
Records in April 2019
- Cleanest half hour
- 99 g 03:00 on Saturday 27 April
- Dirtiest half hour
- 309 g 19:00 on Thursday 11 April
- Most wind
- 40.6% 23:30 on Friday 26 April
- Most solar
- 30.3% 13:30 on Sunday 21 April
- Most low-carbon
- 74.5% 13:30 on Monday 22 April
- Least gas
- 16.9% 23:30 on Friday 26 April
- Cleanest day
- 134 g Saturday 27 April
- Dirtiest day
- 274 g Thursday 11 April
- Windiest day
- 30.4% wind Saturday 27 April
- Sunniest day
- 9.6% solar Saturday 20 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 31 October 2026.