In May 2019, Britain's electricity averaged 210 gCO₂/kWh, in the moderate band (140–219 g). That is about the same as April 2019 (212 g). Gas made 43.1% of the electricity generated, nuclear 21.6%, wind 12.2% and imports 8.4%; low-carbon sources together made 48.3%. The cleanest half hour was 75 g at 13:30 on Sunday 26 May, and the dirtiest 302 g at 06:00 on Tuesday 7 May. Sunday 26 May was both the cleanest day (105 g on average) and the windiest (30.6% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 May | 270 | 35.8% | 3.0% | 4.1% | 56.0% | 48 |
| Thu 2 May | 233 | 43.7% | 10.0% | 4.7% | 48.6% | 48 |
| Fri 3 May | 223 | 45.1% | 12.5% | 3.3% | 46.3% | 48 |
| Sat 4 May | 127 | 67.7% | 27.5% | 8.7% | 25.2% | 48 |
| Sun 5 May | 182 | 53.8% | 16.8% | 6.0% | 37.7% | 48 |
| Mon 6 May | 240 | 41.9% | 7.7% | 5.3% | 50.6% | 48 |
| Tue 7 May | 266 | 35.8% | 4.7% | 5.2% | 57.6% | 48 |
| Wed 8 May | 189 | 51.5% | 22.2% | 3.0% | 41.2% | 48 |
| Thu 9 May | 240 | 42.4% | 12.9% | 3.2% | 51.2% | 48 |
| Fri 10 May | 267 | 36.0% | 3.3% | 5.7% | 56.1% | 48 |
| Sat 11 May | 224 | 46.0% | 7.3% | 7.5% | 45.3% | 48 |
| Sun 12 May | 221 | 46.7% | 4.4% | 9.7% | 44.4% | 48 |
| Mon 13 May | 221 | 46.0% | 7.0% | 9.1% | 47.3% | 48 |
| Tue 14 May | 224 | 45.9% | 7.4% | 9.2% | 49.4% | 48 |
| Wed 15 May | 220 | 45.4% | 7.8% | 8.6% | 45.5% | 48 |
| Thu 16 May | 182 | 54.9% | 17.2% | 8.1% | 35.3% | 48 |
| Fri 17 May | 210 | 47.9% | 15.1% | 3.2% | 42.1% | 48 |
| Sat 18 May | 238 | 41.4% | 5.8% | 4.4% | 46.8% | 48 |
| Sun 19 May | 239 | 41.3% | 4.0% | 5.9% | 47.1% | 48 |
| Mon 20 May | 246 | 39.6% | 5.4% | 6.4% | 51.7% | 48 |
| Tue 21 May | 239 | 42.4% | 7.4% | 8.1% | 49.6% | 48 |
| Wed 22 May | 222 | 44.3% | 10.8% | 8.0% | 46.3% | 48 |
| Thu 23 May | 192 | 52.7% | 15.7% | 8.3% | 38.5% | 48 |
| Fri 24 May | 195 | 52.0% | 14.7% | 7.0% | 39.4% | 48 |
| Sat 25 May | 197 | 50.9% | 8.7% | 7.7% | 38.8% | 48 |
| Sun 26 May | 105 | 73.1% | 30.6% | 5.9% | 17.4% | 48 |
| Mon 27 May | 159 | 60.8% | 17.8% | 7.0% | 31.0% | 48 |
| Tue 28 May | 218 | 45.7% | 8.4% | 6.0% | 45.5% | 48 |
| Wed 29 May | 209 | 46.2% | 12.7% | 3.6% | 43.5% | 48 |
| Thu 30 May | 145 | 62.3% | 25.5% | 6.1% | 27.8% | 48 |
| Fri 31 May | 160 | 58.6% | 22.7% | 5.3% | 31.8% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in May 2019, 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): 68 hours, 9%
- Moderate (140–219 g): 317 hours, 43%
- High (220–299 g): 359 hours, 48%
- Very high (300 g or more): 1 hours, 0%
Records in May 2019
- Cleanest half hour
- 75 g 13:30 on Sunday 26 May
- Dirtiest half hour
- 302 g 06:00 on Tuesday 7 May
- Most wind
- 36.8% 03:00 on Thursday 30 May
- Most solar
- 26.6% 12:30 on Tuesday 14 May
- Most low-carbon
- 79.8% 06:00 on Sunday 26 May
- Least gas
- 10.2% 13:30 on Sunday 26 May
- Cleanest day
- 105 g Sunday 26 May
- Dirtiest day
- 270 g Wednesday 1 May
- Windiest day
- 30.6% wind Sunday 26 May
- Sunniest day
- 9.7% solar Sunday 12 May
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.