In March 2019, Britain's electricity averaged 197 gCO₂/kWh, in the moderate band (140–219 g). That is 9% cleaner than February 2019 (216 g). Gas made 37.5% of the electricity generated, wind 21.8%, nuclear 18.1% and imports 9.2%; low-carbon sources together made 51.6%. The cleanest half hour was 84 g at 01:30 on Monday 25 March, and the dirtiest 326 g at 17:00 on Monday 18 March. The cleanest day was Sunday 17 March (131 g on average); the windiest was Wednesday 13 March (33.8% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Fri 1 Mar | 278 | 34.1% | 6.7% | 1.2% | 54.6% | 48 |
| Sat 2 Mar | 168 | 53.4% | 24.9% | 2.7% | 34.9% | 48 |
| Sun 3 Mar | 159 | 57.3% | 30.7% | 1.0% | 33.7% | 48 |
| Mon 4 Mar | 164 | 55.5% | 26.7% | 3.3% | 35.3% | 48 |
| Tue 5 Mar | 215 | 46.9% | 19.0% | 3.3% | 42.1% | 48 |
| Wed 6 Mar | 177 | 55.2% | 26.4% | 1.3% | 33.4% | 48 |
| Thu 7 Mar | 168 | 59.1% | 28.4% | 2.5% | 28.2% | 48 |
| Fri 8 Mar | 208 | 50.1% | 21.1% | 1.8% | 37.7% | 48 |
| Sat 9 Mar | 144 | 63.0% | 31.8% | 4.2% | 27.6% | 48 |
| Sun 10 Mar | 170 | 55.9% | 26.0% | 4.1% | 33.6% | 48 |
| Mon 11 Mar | 168 | 58.8% | 30.0% | 4.9% | 29.8% | 48 |
| Tue 12 Mar | 179 | 55.6% | 31.9% | 1.4% | 32.5% | 48 |
| Wed 13 Mar | 162 | 59.5% | 33.8% | 3.2% | 28.0% | 48 |
| Thu 14 Mar | 165 | 58.6% | 31.6% | 3.9% | 29.3% | 48 |
| Fri 15 Mar | 154 | 60.6% | 31.3% | 2.6% | 28.6% | 48 |
| Sat 16 Mar | 162 | 57.1% | 29.1% | 1.3% | 31.7% | 48 |
| Sun 17 Mar | 131 | 65.0% | 32.6% | 5.5% | 24.6% | 48 |
| Mon 18 Mar | 267 | 37.5% | 8.8% | 2.9% | 50.1% | 48 |
| Tue 19 Mar | 253 | 40.6% | 12.3% | 2.4% | 48.6% | 48 |
| Wed 20 Mar | 221 | 45.0% | 16.3% | 2.9% | 44.8% | 48 |
| Thu 21 Mar | 244 | 42.5% | 13.1% | 2.1% | 46.7% | 48 |
| Fri 22 Mar | 210 | 51.3% | 22.2% | 1.6% | 36.6% | 48 |
| Sat 23 Mar | 218 | 47.7% | 16.4% | 3.9% | 42.3% | 48 |
| Sun 24 Mar | 145 | 62.3% | 27.6% | 7.4% | 28.2% | 48 |
| Mon 25 Mar | 196 | 54.4% | 20.4% | 6.4% | 34.9% | 48 |
| Tue 26 Mar | 245 | 43.7% | 13.4% | 4.9% | 45.4% | 48 |
| Wed 27 Mar | 254 | 41.2% | 12.5% | 3.6% | 47.7% | 48 |
| Thu 28 Mar | 244 | 43.1% | 12.9% | 5.5% | 46.8% | 48 |
| Fri 29 Mar | 227 | 46.7% | 13.6% | 6.4% | 42.4% | 48 |
| Sat 30 Mar | 231 | 45.7% | 9.5% | 6.2% | 44.2% | 48 |
| Sun 31 Mar | 192 | 52.2% | 15.7% | 4.8% | 38.1% | 46 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in March 2019, with February 2019 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Low (70–139 g): 126 hours, 17%
- Moderate (140–219 g): 358 hours, 48%
- High (220–299 g): 240 hours, 32%
- Very high (300 g or more): 19 hours, 3%
Records in March 2019
- Cleanest half hour
- 84 g 01:30 on Monday 25 March
- Dirtiest half hour
- 326 g 17:00 on Monday 18 March
- Most wind
- 45.2% 04:00 on Monday 11 March
- Most solar
- 25.4% 11:00 on Sunday 24 March
- Most low-carbon
- 76.6% 03:30 on Monday 25 March
- Least gas
- 14.3% 02:00 on Monday 25 March
- Cleanest day
- 131 g Sunday 17 March
- Dirtiest day
- 278 g Friday 1 March
- Windiest day
- 33.8% wind Wednesday 13 March
- Sunniest day
- 7.4% solar Sunday 24 March
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.