- Ofgem will oversee an independent investigation into allegations concerning NESO’s decision-making and record-keeping during June’s extreme heat.
- The electricity system moved outside NESO’s normal operating frequency range, but remained within statutory limits. NESO rejects claims that disconnections were imminent.
- The lasting issue is institutional trust: a publicly owned system operator with expanding planning powers must demonstrate that operational decisions are insulated from reputational considerations.
Ofgem has intervened in an investigation into the National Energy System Operator’s (NESO) handling of the UK’s electricity system during June’s heatwave, increasing scrutiny on allegations that senior staff interfered with operational decisions and discouraged proper record-keeping.
The regulator said it would ensure NESO’s externally commissioned review was “transparent, impartial” and governed by appropriate terms of reference.
The allegations concern the period from 22 to 26 June and include claims that system risk data may have been hidden, and that operational decision making was improperly influenced. Ofgem’s statement does not prejudge the claims, aiming to ensure the review can “get to the facts about what happened”.
NESO has appointed an external legal firm to investigate and has said the resulting findings will be published. The firm is expected to interview control room personnel, system managers and corporate affairs staff, as well as examining operational logs and communications. Reuters reported that fieldwork was due to conclude on 23 July, with a final report expected on 31 July.
The allegations, raised in Parliament by Conservative shadow energy secretary Claire Coutinho, include claims that corporate affairs staff sought to influence operational decisions to protect NESO’s reputation. Senior managers were also alleged to have encouraged staff to use documents without permanent version histories, potentially limiting the subsequent audit trail.
NESO says its procedures are designed to prevent such interference and that it is taking the allegations seriously. None has yet been substantiated.
Internal culture questioned
The operational backdrop is challenging and has become shrouded in controversy. On 23 June, grid frequency remained below NESO’s normal operating range of 49.8Hz to 50.2Hz for much of the period between 5.30 pm and 6.30 pm, reaching a low of 49.66Hz. That was outside the operator’s preferred range but above the statutory lower limit of 49.5Hz. NESO maintains that the system remained secure and that customer disconnections were never close.
The heatwave combined several stressors: weaker renewable generation, unplanned gas plant outages and increased cooling demand. NESO issued two electricity margin notices during the final week of June and procured high-priced flexible generation to maintain sufficient headroom.
Those technical questions will be examined separately from the governance investigation. A period of tight margins is not, by itself, evidence of operational failure. System operators routinely use balancing actions, reserve procurement and market notices to prevent tight conditions becoming emergencies.
The more consequential question is whether NESO’s internal culture allowed reputational concerns to affect the control room or the preservation of records. NESO is no longer simply a technical grid operator; as a publicly owned body, it now occupies a central position in network planning, connections reform, market design and the delivery of the government’s clean power ambitions.
That enlarged mandate gives it considerable influence over investment across the energy economy. It also raises the standard of transparency it must meet.
For industry, the inquiry is therefore less about whether Britain narrowly avoided a blackout than whether market participants, ministers and the public can trust the evidence on which system decisions are made.
