Neso Rejects Whistleblower Claims Over June Heatwave Grid Management
UK's National Energy System Operator dismisses allegations its decisions compromised grid security during June's record heat, as separate scrutiny over balancing costs persists.
The UK's National Energy System Operator dismissed allegations from whistleblowers on Wednesday (2026-07-08) that called into question its management of grid security during the system stress that accompanied June's record-breaking heatwave, Montel reported. Neso told Montel that all operational decisions had been made in line with standard procedures, pushing back against claims that its conduct during the heatwave had compromised grid security.5
The rebuttal does not close all scrutiny of the operator. Separately, an analyst told Montel that UK consumers could be paying higher electricity bills partly because of capacity hoarding during interconnector trading with Europe, with parties allegedly submitting bids to Neso's capacity auctions at extremely high prices, well above the imbalance levels subsequently observed, according to regulator Ofgem. Operational conduct during peak demand and the cost of securing system balance are now running as parallel concerns against the same organisation.2
Neso's balancing costs are partly determined by what it can transact across interconnectors into Europe. If parties are gaming the capacity auction for those flows, the cost lands on UK consumers and raises questions for Ofgem about auction design rather than just individual conduct. Ofgem has already flagged the auction bidding pattern, noting instances where bids were submitted at levels far exceeding what the imbalance price subsequently turned out to be — a distinction between manipulation and legitimate uncertainty hedging that only a formal investigation could draw.2
NBP gas front-month was trading at €45.52 on Friday (2026-07-10) morning, up 1.92% on the day, reflecting the degree to which gas-fired generation remains the marginal price-setter in the UK during periods of high demand.
The June heatwave that prompted the whistleblower allegations created exactly the system conditions that expose the gap between a grid built around dispatchable fossil generation and one being reshaped by variable renewables. When demand spikes and wind output is low, balancing costs rise and the margin for operational error narrows.5
The broader European grid context explains why such pressures are likely to recur. On the continent, requests to connect renewable capacity are outstripping grid infrastructure across multiple countries. Montenegro's transmission system operator warned in May (2026-05-12) that its grid holds roughly 1 GW of capacity against around 7 GW of grid connection requests, an imbalance generating unintended cross-border flows into neighbouring systems, Ivan Asanovic, CEO of CGES, told an energy event in Belgrade.4
Europe's major operators are responding with unprecedented capital commitments. TenneT, the Netherlands' sole TSO and Germany's largest, plans to spend around €200bn by 2034, while France's RTE has budgeted €100bn between 2025 and 2040. The EU TSO body Entso-E estimates the total needed to meet EU electrification targets by 2050 at around €800bn.3
The UK, operating outside that coordinated European framework since Brexit, manages interconnector flows to a continent undergoing this transformation without the same planning structures. That position gives Neso less visibility into the cross-border capacity picture and more exposure to the pricing dynamics that are now drawing Ofgem's scrutiny.1
Neso's rejection of the whistleblower claims settles one immediate question about June's heatwave. Ofgem's documented concern about auction bidding patterns is the longer-running thread — whether the regulator advances from flagging conduct to opening a formal probe will shape how interconnector capacity is priced in the next period of system stress.