RIIO-3 Final Determinations. £28.1 billion upfront within a £90 billion pipeline.

Ofgem approved RIIO-3 Final Determinations for electricity transmission, gas transmission and gas distribution — £28.1 billion of upfront funding (a 16% increase on Draft Determinations) within a wider ~£90 billion investment pipeline across the 2026-2031 control period. The Sector Specific Methodology Decision was published 13 December 2023; the control period runs 1 April 2026 to 31 March 2031.

For National Gas Transmission and the four Gas Distribution Networks (Cadent, Northern Gas Networks, SGN, Wales & West Utilities), RIIO-GT3 and RIIO-GD3 are the first UK gas network price controls to operate during a structural gas demand decline. The strategic challenge is unprecedented: how to fund safe and reliable network operation while customer base + throughput fall, how to allocate stranded asset risk, how to invest in hydrogen readiness without certainty on the hydrogen for heat pathway, and how to maintain customer bill affordability under fewer customers funding similar network costs.

For electricity transmission and distribution, RIIO-ET3 and RIIO-ED3, the framework supports concurrent demand growth from heat decarbonisation (heat pumps), data centre cluster build-out, AI Growth Zone development and the Clean Power 2030 generation mix. Whole-system thinking, gas + electricity sector transition coordination, sits at the centre of the regulatory innovation. PR24 water sector lessons (RAPID gated SROs, the Bioresources market, Water Special Measures Act 2025 enforcement) inform cross-utility coordination.

Customer bills sit alongside PR24 water bill pressures and electricity bill profile under the same affordability constraint. Fuel poverty + cost recovery sustainability + investor confidence + cross-utility regulatory coordination shape the next five years.

GridteamAI's Gap 43 report decodes RIIO-GT3 + GD3 — the framework, the strategic challenges, the network operator positions, the hydrogen readiness investment direction, the gas grid exit pathway preparation, and the cross-volume integration with hydrogen production (Gap 13), CCUS (Gap 33), heat networks (Gap 14), heat decarbonisation (Gap 46) and gas market reform (Gap 47).