Ofgem Sets Timetable for June Heat Electricity Inquiry

Great Britain’s electricity-system operations during the heat of 22–26 June 2026 remain under review, with Ofgem yet to reach regulatory judgments on the events or operational actions described in NESO’s preliminary report. The regulator published that report alongside an inquiry update and outlined its timetable in a statement dated 19 October.

Ofgem said the inquiry covers system security, planning and forecasts by NESO, operational decisions, generator availability, balancing services and market responses. It also includes electricity flows through interconnectors. According to NESO, these high-voltage cable systems connect networks across countries or regions for electricity transfers and trading, and the operator can limit flows when system conditions require.

Using its regulatory powers, Ofgem commissioned NESO to review the week beginning 22 June. The resulting preliminary document records the sequence of events and actions taken, rather than offering recommendations or final conclusions. NESO describes the heat during the five-day period as exceptional and examines changing conditions affecting electricity demand, available generation, networks and market activity.

In a published NESO account, Craig Dyke, its Director of System Operations, said an Electricity Margin Notice issued on 23 June covered peak demand the next evening. The notice was withdrawn on 24 June following an improvement in margins. NESO says such notices ask market participants to identify capacity because more generation may be required; a notice does not, by itself, indicate imminent power cuts.

In a separate account published on 13 July, Dyke said there had been no disconnection of customer demand during 22–26 June and that voltage had stayed within its limits. Frequency also remained inside the statutory band, whose lower and upper limits are 49.5 Hz and 50.5 Hz. NESO recorded a minimum of 49.66 Hz. Those statements and measurements are the operator’s account, not a final determination by Ofgem.

Based on evidence available by 9 September, NESO’s preliminary report considers weather, generation availability, market behaviour, interconnector flows, transmission constraints and system operations. It says additional analysis is necessary to establish the contribution of each factor and assess the effectiveness of the responses.

Ofgem said it expected to release its conclusions about system security and compliance with security standards by 31 January 2027 at the latest. For conclusions concerning lessons from the events, the regulator set a deadline of 31 March 2027.

According to Ofgem, any enforcement investigation would be conditional on the inquiry establishing material grounds to believe that a licensee had failed to meet its obligations. The update did not announce an enforcement investigation.

* This article is based on publicly available information at the time of writing.