The National Energy System Operator (Neso), a government-backed body responsible for balancing Britain's electricity, is facing accusations of downplaying a near-catastrophic energy crisis that occurred on June 23 during a severe heatwave. Whistleblowers have reportedly alerted Shadow Energy Secretary Claire Coutinho, claiming that Neso bosses were more concerned with the reputational damage of admitting grid instability than addressing operational failures. These sources allege that staff were instructed not to keep records of operational decisions to avoid public disclosure through Freedom of Information requests, and that corporate affairs staff interfered with control room operators.
Grid Instability During Heatwave
On June 23, as temperatures soared to 37C, Neso's control room engineers reportedly panicked as the national grid's frequency destabilized and dropped below strict operating limits, threatening widespread blackouts. This situation bore similarities to a 2025 blackout in Spain and Portugal, which caused disruptions to transportation, industry, and forced hospitals onto emergency power.
Neso, established under the Energy Act 2023, is tasked with ensuring the lights stay on and preparing the grid for the transition to Net Zero. Its sole shareholder is the Secretary of State for Energy Security and Net Zero. The organization, which employs approximately 2,200 people, recorded a loss of £409 million in 2024/25, with costs borne by taxpayers.
Challenges of Renewable Energy Integration
The increasing reliance on weather-dependent renewable sources like solar and wind power is making grid balancing more challenging. Unlike fossil fuel or nuclear power plants, renewable generation cannot be easily controlled to match demand. Experts note that as renewable energy constitutes a larger portion of the energy mix, the ability of grid operators to manage supply and demand fluctuations is diminished.
Neso's own interactive game simulating grid operation illustrates the complexity of maintaining the grid's frequency close to 50Hz. Operators must constantly adjust supply and demand, which is complicated by the intermittent nature of renewables. The game highlights that while renewable generation cannot be controlled at will, other sources can be adjusted, but this requires accurate weather forecasting.
Concerns Over Net Zero Targets
The incident has raised questions about the feasibility and cost of ambitious Net Zero targets. Ed Miliband, the current Secretary of State for Energy Security and Net Zero, has previously advocated for a carbon-free electricity grid by 2030. However, the estimated cost for grid upgrades to achieve this target has significantly increased, from £58 billion to £89 billion. Some experts, including Professor Sir Dieter Helm, question the attainability of such targets, while others, like Gary Smith of the GMB union, point to global supply chain limitations for necessary infrastructure like offshore wind farms.
Furthermore, Neso's plans for achieving a 95% carbon-free electricity system by 2030 include a need for "consumer-led flexibility," potentially involving price surges during peak demand times when supply is strained. Critics suggest that customers will ultimately bear the cost of this transition, either through blackouts or increased energy prices.
In response to the June 23 events, the government has confirmed an independent inquiry into what transpired. Neso's Chief Executive, Fintan Slye, reportedly told staff that allegations of breached grid security standards were false and criticized whistleblowers for their concerns.