Persistent cloud drops British Isles solar output in early February

Cloud-bearing weather systems dominated the British Isles, significantly reducing irradiance and solar generation across the UK and Ireland between 9 and 18 February 2025. Persistent cloud cover first arrived from the east under the influence of a Scandinavian high-pressure system and was followed by clouds from the Atlantic. This combination resulted in historically low PV output, with Ireland most severely impacted.

Between 9 and 18 February, solar generation across the British Isles reached its lowest levels relative to capacity in at least a decade. Analysis of the distribution network in the UK revealed that all Distribution Network Operator regions, except for UK Power Networks (UKPN) in southeast England, recorded their lowest PV generation for this time of year in ten years. The UKPN region saw its second-lowest February performance in the same period. 

The Northern Power Grid (NPG) distribution area, covering northeast England, was among the hardest hit, with generation down 56% compared to normal levels. Other Distribution Network Operator areas, including Scottish Power Energy Networks (SPEN), Scottish and Southern Electricity Networks (SSEN), Electricity North West Limited Grid (ENWL), and National Grid Electricity Distribution (NGED) also saw reductions of 30%-39%.

The first phase of prolonged cloud cover was driven by an easterly flow linked to a Scandinavian high pressure system. This setup channeled low-level cloud over the British Isles, reducing solar irradiance across much of the region. Later in the period, a strong jet stream over the Atlantic intensified frontal systems, which moved in from the west and brought widespread cloud and rainfall. These systems suppressed irradiance, particularly across Ireland and many parts of Great Britain, taking solar output below seasonal norms.

Some locations in Ireland and Great Britain recorded their lowest solar irradiance levels in 18 years, across the 9 to 18 February period. For example, Dublin saw mean daily irradiance drop to 0.45 kWh, while Belfast recorded an even lower 0.42 kWh. Newcastle upon Tyne, which fared slightly better with a mean daily irradiance of 0.65 kWh, was still at its lowest mark in 18 years. Great Britain was not as strongly affected as Ireland, as it was less influenced by the Atlantic weather systems. However, Ireland remained under persistent cloud cover throughout the period, leading to its particularly low overall irradiance.

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