Wind Lulls in 2025
The Electricity System Operator for Great Britain (ESO) publishes its Future Energy Scenarios (FES) every year. Every year they show a significant increase in installed wind turbine capacity connected to the National Grid.
They also acknowledge a problem referred to as “Dunkelflaute”. This is a period when there is little or no wind – a wind lull.
The table below shows the periods when wind contributed less than 10% of grid demand in the first half of 2025 and confirms that “Dunkelflaute” has a significant effect on the contribution of wind to demand.
| Month | Total Hours <10% | No of Lulls | No of Lulls >5 hours | No of Lulls >10 hours | Maximum Lull (hours) |
| 2025 | | | | | |
| January | 165 | 13 | 6 | 6 | 51 |
| February | 24 | 5 | 2 | 1 | 12.5 |
| March | 103.5 | 13 | 7 | 4 | 34.5 |
| April | 168 | 11 | 9 | 7 | 47.5 |
| May | 70.5 | 10 | 5 | 4 | 19.5 |
| June | 54 | 6 | 4 | 2 | 21 |
| TOTAL | 585 | 58 | 33 | 24 | |
The table confirms not only that low wind speeds occur, but that they are frequent and often extended.
Have the wind lulls decreased over the past 3 years with more and more wind turbines being connected to the grid? The table below compares the above with 2023 and 2024.
| Month | Total Hours <10% | No of Lulls >10 hours |
| | 2023 | 2024 | 2025 | 2023 | 2024 | 2025 |
| January | 30 | 22 | 165 | 1 | 0 | 6 |
| February | 57 | 92 | 24 | 2 | 3 | 1 |
| March | 96 | 90.5 | 103.5 | 4 | 2 | 4 |
| April | 137 | 57.5 | 168 | 5 | 2 | 7 |
| May | 146.5 | 264 | 70.5 | 6 | 6 | 4 |
| June | 150.5 | 98.5 | 54 | 3 | 4 | 2 |
| TOTAL | 617 | 624.5 | 585 | 21 | 23 | 24 |
| | | | | | | |
The table confirms that there is little difference between the total number of hours when wind contributed less than 10% between 2023, 2024 and 2025 despite the increase in generating capacity. It also confirms that extended wind lulls, greater than 10 hours in duration, have not reduced in numbers.
Looking at the extended wind lulls in more detail.
| Month | Maximum Lull (hours) | Although May 2024 exhibited a wind lull of lull of 93 hours, the data for 2025 is more concerning as January, March and April 2025, all colder months, show the longest lulls over the three years. |
| | 2023 | 2024 | 2025 |
| January | 18 | 7 | 51 |
| February | 15 | 38 | 12.5 |
| March | 20.5 | 29 | 34.5 |
| April | 31.5 | 23.5 | 47.5 |
| May | 27 | 93 | 19.5 |
| June | 55.5 | 31.5 | 21 |
| | | | |
The shortfall was met by gas and interconnectors but by 2050 there will be little gas and how reliant should we be on interconnectors?
Looking at periods when wind contributes less than 15% of demand shows a significant increase over the 10% lulls. Both the total hours and the maximum wind lull are about twice that of the 10% figures.
| Month | Total Hours <15% | No of Lulls | No of Lulls >5 hours | No of Lulls >10 hours | Maximum Lull (hours) |
| 2025 | | | | | |
| January | 236 | 12 | 7 | 6 | 104 |
| February | 113 | 13 | 8 | 4 | 25 |
| March | 233 | 18 | 11 | 8 | 54.5 |
| April | 286.5 | 14 | 9 | 9 | 83 |
| May | 175.5 | 15 | 9 | 6 | 38.5 |
| June | 95.5 | 11 | 5 | 4 | 26.5 |
| TOTAL | 1139.5 | 83 | 49 | 37 | |
Assuming weather patterns remain the same in future years, it can also be assumed that wind lulls will not significantly decrease as the capacity of operational wind turbines is increased.
A document from ESO, Clean Power 2030, commissioned by Ed Miliband and published last year, shows an increase in offshore wind capacity from 14.7GW in 2023 to 50.6GW by 2030 and an increase in onshore wind from 13.7GW to 27.3GW.
Obviously a reliance on a strategy where wind represents 80% of generating capacity is not sound and having recognised that wind lulls exist, the National Grid should revisit their strategy.