In April 2020, Britain's electricity averaged 168 gCO₂/kWh, in the moderate band (140–219 g). That is 11% cleaner than March 2020 (189 g), and 21% cleaner than April 2019 (212 g). Gas made 32.3% of the electricity generated, nuclear 20.9%, wind 19.2% and imports 9.6%; low-carbon sources together made 57.2%. The cleanest half hour was 72 g at 22:00 on Monday 20 April, and the dirtiest 309 g at 21:00 on Wednesday 8 April. The cleanest day was Monday 20 April (93 g on average); the windiest was Sunday 5 April (43.9% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 Apr | 232 | 42.1% | 18.3% | 3.1% | 46.1% | 48 |
| Thu 2 Apr | 171 | 59.0% | 31.5% | 4.6% | 27.2% | 48 |
| Fri 3 Apr | 243 | 41.4% | 13.6% | 4.9% | 44.8% | 48 |
| Sat 4 Apr | 179 | 55.2% | 23.0% | 7.3% | 30.9% | 48 |
| Sun 5 Apr | 103 | 76.7% | 43.9% | 8.6% | 18.3% | 48 |
| Mon 6 Apr | 140 | 66.6% | 31.5% | 7.7% | 26.7% | 48 |
| Tue 7 Apr | 200 | 54.4% | 18.3% | 8.3% | 37.5% | 48 |
| Wed 8 Apr | 239 | 46.1% | 10.7% | 7.3% | 45.2% | 48 |
| Thu 9 Apr | 222 | 47.7% | 11.0% | 7.8% | 41.9% | 48 |
| Fri 10 Apr | 191 | 50.8% | 12.9% | 8.8% | 38.9% | 48 |
| Sat 11 Apr | 159 | 58.8% | 20.8% | 9.1% | 31.3% | 48 |
| Sun 12 Apr | 163 | 56.0% | 16.3% | 7.6% | 32.9% | 48 |
| Mon 13 Apr | 130 | 64.2% | 23.3% | 8.4% | 27.3% | 48 |
| Tue 14 Apr | 190 | 52.2% | 11.6% | 9.0% | 36.9% | 48 |
| Wed 15 Apr | 175 | 56.9% | 13.5% | 9.5% | 32.7% | 48 |
| Thu 16 Apr | 174 | 56.2% | 12.5% | 8.2% | 33.0% | 48 |
| Fri 17 Apr | 120 | 68.8% | 26.9% | 5.7% | 22.4% | 48 |
| Sat 18 Apr | 175 | 54.8% | 18.2% | 4.2% | 35.0% | 48 |
| Sun 19 Apr | 125 | 67.9% | 24.9% | 10.1% | 23.3% | 48 |
| Mon 20 Apr | 93 | 76.9% | 37.1% | 10.1% | 19.6% | 48 |
| Tue 21 Apr | 94 | 76.1% | 37.3% | 9.9% | 19.8% | 48 |
| Wed 22 Apr | 118 | 68.0% | 28.8% | 9.7% | 24.2% | 48 |
| Thu 23 Apr | 177 | 52.8% | 9.8% | 8.8% | 34.3% | 48 |
| Fri 24 Apr | 199 | 48.0% | 5.1% | 8.3% | 36.2% | 48 |
| Sat 25 Apr | 185 | 50.9% | 5.2% | 8.9% | 33.5% | 48 |
| Sun 26 Apr | 173 | 54.9% | 9.4% | 8.6% | 30.7% | 48 |
| Mon 27 Apr | 200 | 47.6% | 7.3% | 5.7% | 38.5% | 48 |
| Tue 28 Apr | 194 | 45.9% | 10.1% | 1.8% | 41.3% | 48 |
| Wed 29 Apr | 156 | 55.2% | 16.5% | 4.2% | 32.3% | 48 |
| Thu 30 Apr | 123 | 62.6% | 25.1% | 4.8% | 25.5% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in April 2020, with April 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 228 hours, 32%
- Moderate (140–219 g): 384 hours, 53%
- High (220–299 g): 106 hours, 15%
- Very high (300 g or more): 3 hours, 0%
Records in April 2020
- Cleanest half hour
- 72 g 22:00 on Monday 20 April
- Dirtiest half hour
- 309 g 21:00 on Wednesday 8 April
- Most wind
- 52.0% 01:00 on Monday 6 April
- Most solar
- 30.6% 13:00 on Sunday 19 April
- Most low-carbon
- 83.4% 11:30 on Sunday 5 April
- Least gas
- 13.5% 11:00 on Sunday 5 April
- Cleanest day
- 93 g Monday 20 April
- Dirtiest day
- 243 g Friday 3 April
- Windiest day
- 43.9% wind Sunday 5 April
- Sunniest day
- 10.1% solar Sunday 19 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 29 October 2026.