IN Brief:
- Ofgem has opened consultation on draft RIIO-ET3 electricity transmission reporting guidance.
- The consultation covers RIGs, regulatory reporting packs, the transmission glossary, and NARM reporting.
- Responses are due by close of business on 25 August 2026.
Ofgem has opened consultation on the proposed annual reporting framework for the onshore electricity transmission sector during the RIIO-ET3 price control period.
The consultation was published on 30 June 2026 and remains open until 25 August 2026. It covers draft updates for the RIIO-ET3 period from 2026 to 2031, including Regulatory Instructions and Guidance, the regulatory reporting pack data template, the transmission glossary, and network asset risk metric reporting.
The reporting documents set out how electricity transmission companies report cost, output, and performance data to Ofgem. The proposals are intended to improve clarity, consistency, and comparability, align reporting requirements with RIIO-ET3 decisions, and support regulatory monitoring.
The consultation has been informed by RIIO-ET3 business plan template assessment work, data review, and stakeholder engagement. Onshore electricity transmission network companies are identified as the primary respondents. Responses are requested by close of business on 25 August 2026.
The documents include the RIIO-ET3 Annual Reporting Framework consultation, consultation notice, draft Regulatory Instructions and Guidance document, draft Regulatory Reporting Pack template, draft Transmission Glossary, RIIO-3 NARM consultation document, NARM RIGs document, and NARM reporting template.
Although the consultation is administrative in form, it sits directly behind transmission delivery. The RIIO-ET3 period covers a critical phase for the onshore transmission system, with reinforcement, replacement, offshore integration, renewable connection, and asset-health programmes all moving through regulatory scrutiny.
Reporting frameworks influence how network companies evidence delivery, manage cost allowances, track outputs, and demonstrate asset-risk reduction. The structure of a reporting pack shapes the information base on which monitoring, future determinations, and investment scrutiny depend.
The inclusion of NARM reporting gives the consultation additional operational weight. The Network Asset Risk Metric is used to assess asset-health risk and the effect of interventions across the network. As transmission owners increase replacement and reinforcement work, consistent asset-risk reporting helps distinguish between expenditure that adds capacity and expenditure that reduces deterioration, failure probability, or service risk.
RIIO-ET3 arrives as the electricity system faces a major expansion requirement. Offshore wind connections, north-south power flows, interconnection, new demand from electrification, and replacement of ageing assets all place pressure on the transmission network. The regulatory framework must therefore handle both capital delivery and the operational risk of an increasingly loaded system.
Network innovation funding has also moved into sharper focus as electricity demand growth from EV charging, heat pumps, data centres, industrial electrification, and distributed generation creates new operating demands across GB networks. The current RIIO-ET3 reporting consultation sits at the formal regulatory end of the same pressure: networks must evidence performance, investment outcomes, and asset risk with consistent data.
The consultation also lands in a period where transmission investment is attracting growing public attention. New substations, overhead lines, underground cables, and grid reinforcements are increasingly visible in planning and community debates. Regulatory transparency around cost, delivery, outputs, and asset condition will be important in maintaining confidence that spending is controlled and justified.
For transmission companies, the proposed guidance will determine how data is structured and submitted over the five-year price control. That includes cost categories, definitions, performance measures, asset-risk treatment, and glossary alignment. Small inconsistencies in reporting definitions can create large problems when comparing delivery across companies or assessing whether outputs have been met.
The framework will also affect suppliers indirectly. Contractors, equipment manufacturers, engineering consultancies, and asset-management providers all operate within the delivery programmes that transmission owners report to Ofgem. Clearer reporting can sharpen requirements around evidence, asset data, project outputs, and handover documentation.
The practical value of the consultation lies in accountability. Transmission investment must expand quickly, while regulatory oversight still needs comparable data, clear definitions, and a consistent view of performance. RIIO-ET3 reporting will help determine whether network reinforcement, asset renewal, and system-resilience spending can be tracked at the level required for the scale of investment now entering the system.
