In March 2023, Britain's electricity averaged 158 gCO₂/kWh, in the moderate band (140–219 g). That is 5% cleaner than February 2023 (166 g), and 15% cleaner than March 2022 (186 g). Gas made 34.1% of the electricity generated, wind 30.5%, nuclear 13.1% and imports 12.5%; low-carbon sources together made 53.0%. The cleanest half hour was 40 g at 10:30 on Wednesday 22 March, and the dirtiest 301 g at 21:00 on Tuesday 7 March. The cleanest day was Friday 24 March (62 g on average); the windiest was Wednesday 22 March (56.3% wind).
Carbon intensity, day by day
Day by day, as a table
| Day | gCO₂/kWh | Low-carbon | Wind | Solar | Gas | Half hours |
|---|---|---|---|---|---|---|
| Wed 1 Mar | 230 | 39.0% | 20.0% | 1.5% | 53.3% | 48 |
| Thu 2 Mar | 247 | 34.7% | 13.6% | 3.3% | 56.8% | 48 |
| Fri 3 Mar | 249 | 32.4% | 12.5% | 1.3% | 56.3% | 48 |
| Sat 4 Mar | 238 | 33.9% | 12.5% | 1.3% | 53.6% | 48 |
| Sun 5 Mar | 244 | 31.9% | 7.9% | 1.5% | 54.2% | 48 |
| Mon 6 Mar | 223 | 43.1% | 24.3% | 1.6% | 50.0% | 48 |
| Tue 7 Mar | 257 | 35.1% | 14.2% | 2.9% | 54.0% | 48 |
| Wed 8 Mar | 235 | 36.0% | 16.7% | 1.3% | 50.3% | 48 |
| Thu 9 Mar | 188 | 47.2% | 27.7% | 0.9% | 38.6% | 48 |
| Fri 10 Mar | 159 | 51.9% | 30.8% | 2.6% | 32.9% | 48 |
| Sat 11 Mar | 186 | 41.6% | 19.3% | 3.3% | 38.9% | 48 |
| Sun 12 Mar | 70 | 75.8% | 52.7% | 3.0% | 11.7% | 48 |
| Mon 13 Mar | 63 | 77.0% | 55.7% | 2.3% | 11.4% | 48 |
| Tue 14 Mar | 130 | 59.7% | 35.9% | 4.4% | 27.0% | 48 |
| Wed 15 Mar | 193 | 43.7% | 22.3% | 2.4% | 42.9% | 48 |
| Thu 16 Mar | 100 | 67.4% | 47.0% | 1.8% | 18.7% | 48 |
| Fri 17 Mar | 168 | 45.7% | 23.1% | 3.0% | 36.4% | 48 |
| Sat 18 Mar | 159 | 47.2% | 22.8% | 3.5% | 35.4% | 48 |
| Sun 19 Mar | 160 | 48.5% | 22.5% | 4.6% | 34.8% | 48 |
| Mon 20 Mar | 181 | 47.1% | 26.8% | 1.5% | 41.8% | 48 |
| Tue 21 Mar | 98 | 70.6% | 49.0% | 3.4% | 21.3% | 48 |
| Wed 22 Mar | 67 | 76.4% | 56.3% | 4.1% | 14.1% | 48 |
| Thu 23 Mar | 74 | 74.3% | 51.1% | 4.0% | 14.9% | 48 |
| Fri 24 Mar | 62 | 72.3% | 46.1% | 4.8% | 13.5% | 48 |
| Sat 25 Mar | 97 | 66.7% | 38.6% | 5.0% | 19.8% | 48 |
| Sun 26 Mar | 128 | 55.5% | 28.6% | 3.0% | 26.1% | 46 |
| Mon 27 Mar | 188 | 45.2% | 17.1% | 5.9% | 40.1% | 48 |
| Tue 28 Mar | 145 | 57.6% | 35.6% | 1.2% | 30.8% | 48 |
| Wed 29 Mar | 128 | 61.3% | 40.1% | 1.4% | 27.6% | 48 |
| Thu 30 Mar | 106 | 64.6% | 40.2% | 4.4% | 22.6% | 48 |
| Fri 31 Mar | 120 | 59.4% | 35.5% | 2.1% | 26.4% | 48 |
What powered the grid
Each fuel's average share of the electricity generated in Great Britain in March 2023, with March 2022 beneath it for comparison. Imports count as one source, as NESO counts them.
Hours in each carbon band
- Very low (under 70 g): 102 hours, 14%
- Low (70–139 g): 208 hours, 28%
- Moderate (140–219 g): 239 hours, 32%
- High (220–299 g): 194 hours, 26%
- Very high (300 g or more): 1 hours, 0%
Records in March 2023
- Cleanest half hour
- 40 g 10:30 on Wednesday 22 March
- Dirtiest half hour
- 301 g 21:00 on Tuesday 7 March
- Most wind
- 69.0% 04:30 on Monday 13 March
- Most solar
- 18.4% 13:00 on Monday 27 March
- Most low-carbon
- 86.6% 04:30 on Monday 13 March
- Least gas
- 6.3% 12:00 on Sunday 12 March
- Cleanest day
- 62 g Friday 24 March
- Dirtiest day
- 257 g Tuesday 7 March
- Windiest day
- 56.3% wind Wednesday 22 March
- Sunniest day
- 5.9% solar Monday 27 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 24 October 2026.