Britain's largest community solar project, Derril Water in North Devon, has been unexpectedly forced to cease operations for the duration of its first summer. The shutdown, mandated by the government's energy system operator, the National Energy System Operator (Neso), aims to prevent the local power grid from being overloaded with renewable energy, particularly from a surge in rooftop solar installations in the area.
The decision to halt generation came weeks before a period of record high temperatures across Europe, which had led to warnings about power supply. According to the cooperative's board, the shutdown was enforced without warning, with Neso understood to have directed National Grid to switch off a critical 'super grid transformer' to prevent voltage levels from exceeding safety limits. This measure was deemed necessary due to the difficulty in managing high volumes of rooftop solar power during long, sunny summer days, which can generate more electricity than a local grid can safely handle.
The financial ramifications for the nearly 10,000 members of the cooperative are substantial, with an estimated £2 million in lost revenue before the park is permitted to restart in September. The board of Derril Water, in a letter to its members, expressed that the timing of the shutdown 'could not be worse' and would 'substantially impact' the scheme's finances and its ability to pay members. They also noted that while the exact trigger for the shutdown remained unclear, network operators appeared to have been aware of a looming problem.
Concerns about the North Devon network's capacity issues have reportedly been known since 2023, with specialist equipment upgrades initially slated for installation by the end of 2025. However, these crucial measures were delayed and are now expected to be completed in September this year. The cooperative does not anticipate receiving compensation or insurance to cover the significant loss of income from the solar park, which was funded by £20 million raised directly from its members and a £22 million long-term bank loan.
Derril Water began generating electricity in September 2025, following a challenging period that saw its original developer, Ripple Energy, go into administration in early 2025 due to construction delays and rising costs. Ripple Energy, which had aimed for Derril Water to be a blueprint for consumer-owned solar parks, was subsequently acquired by 1st Energy. Despite the recent setback, the volunteer board stated that most members understand the issue lies with the grid infrastructure, not the solar park itself or its management. A National Grid spokesperson confirmed generation curtailment in the local area to maintain system security and stated they are working with Neso to find solutions to these temporary constraints.