October 2025 was a fascinating month for UK renewable energy, showcasing the dramatic variability inherent in wind and solar generation.
Storm Amy’s Impact
Storm Amy, the first named storm of the 2025/26 season, struck the UK on October 3-4 with exceptional force. The storm brought record-breaking winds, with gusts reaching 92 mph in Northern Ireland (a new October record for the region) and 96 mph at Tyree in northern Scotland. The central pressure dropped to 944 hectopascals, with Baltasound in Shetland recording 947.9 hPa, setting a new UK lowest pressure record for October. However, from a wind energy perspective, the chart shows wind generation peaked around 16,500 MW during the early October period—substantial, but perhaps disappointing given the storm’s intensity, as the strongest winds often force turbines to shut down for safety reasons.
The Dunkelflaute Period
Following Storm Amy, the UK experienced an extended “Dunkelflaute”—a German term meaning “dark wind lull”—characterized by minimal wind and solar generation. Your chart clearly shows this six-day period around October 12-18, where wind generation plummeted to barely noticeable levels (dropping below 5,000 MW for extended periods) while solar output remained minimal due to the seasonal decline and cloud cover. During such events, the UK typically sees wind contributing only 3-4% of electricity needs, with gas-fired plants stepping in to provide around 60% of demand. These events can last from hours to several days and are most common during winter months, with 50-150 hours occurring on average per month during November through January.
Late October Recovery
The final week of October brought renewed wind activity, with multiple depressions tracking across the UK generating wind power consistently above 13,000-17,000 MW. This pattern of variable renewable generation underscores the challenge facing the UK as it pursues its target of 42.9% renewable energy (as of September 2025) while aiming to fully decarbonize the electricity system by 2035.