Page type: primary-anchored (mirrors RIIO-GD3 Final Determinations)
Last updated: 2026-04-05
RIIO-GD3: Gas Distribution Price Control 2026-2031
RIIO-GD3 is Ofgem's price control for the four gas distribution networks in Great Britain, running from 1 April 2026 to 31 March 2031. It sets the revenues, outputs, and incentives for Cadent, Northern Gas Networks (NGN), SGN, and Wales and West Utilities (WWU), which together deliver gas to approximately 22 million homes and businesses.
Ofgem describes RIIO-GD3 as likely the "last steady-state price control" for the sector (GD Annex, para 2.5). The HSE's 30-year Iron Mains Risk Reduction Programme ends in 2032, and government decisions on the long-term future of gas -- hydrogen, decommissioning, managed decline -- are expected during the period. These will reshape regulation from RIIO-GD4 onwards.
Key parameters
| Parameter | Value | Source |
|---|---|---|
| Period | 1 Apr 2026 -- 31 Mar 2031 | GD Annex 1.1 |
| Baseline totex (sector) | GBP 14.6bn (2023/24 prices) | GD Annex 2.3 |
| Repex (pipe replacement) | GBP 6.5bn | GD Annex 2.3 |
| Cost of equity | 6.12% | Finance Annex |
| WACC (semi-nominal, gas) | 5.18% | Overview exec summary |
| TIM sharing factor | 50% (all GDNs) | GD Annex 5.520 |
| Ongoing efficiency | 1.0% pa | GD Annex 2.12 |
| Vulnerability allowance (VCMA) | GBP 165m | GD Annex 2.8 |
| NIA (gas distribution) | GBP 73m | GD Annex 2.8 |
| SIF (cross-sector) | GBP 500m total | Overview |
| GD depreciation (new assets) | Accelerated to 2050 (sum-of-digits) | Overview 7.4 |
What GDNs must deliver
Safety. The Emergency Response Time Licence Obligation requires 97% of gas escapes responded to within 1 hour (uncontrolled) or 2 hours (controlled). For RIIO-GD3, Ofgem has tightened this by banning retrospective downgrading of gas escape classifications and requiring detailed tracking of every breach (GD Annex 3.116-3.127).
Pipe replacement. GBP 6.5bn funds Tier 1 mains replacement under the HSE's Iron Mains Risk Reduction Programme. Tier 1 Mains Decommissioned, Tier 1 Services, and Tier 1 Iron Stubs PCDs track delivery. Non-mandatory repex is funded only where justified regardless of future network use (GD Annex 2.3-2.5).
Shrinkage reduction. Methane emissions from gas leakage account for 90-95% of GDNs' business carbon footprint. RIIO-GD3 tackles this through GBP 51.9m for Advanced Leakage Detection technology, the Digital Platform for Leakage Analytics (DPLA), and a new 7- and 28-Day Repair Standards financial incentive. A direct shrinkage incentive is deferred to RIIO-GD4 pending DPLA rollout (GD Annex 3.4-3.7).
Customer service. Customer satisfaction ODI-F thresholds are set above 9 out of 10. The Collaborative Streetworks incentive is expanded from London to nationwide, with GBP 95,000 per minimum project and GBP 160,000 per strategic project (GD Annex 3.234-3.251).
Vulnerability. GBP 165m dedicated VCMA allowance for supporting consumers in vulnerable situations and carbon monoxide safety, governed by an ISG-led National Steering Panel (GD Annex 2.8).
How uncertainty is managed
RIIO-GD3 includes a wide suite of uncertainty mechanisms reflecting the uncertain gas future:
- Heat Policy Re-opener: triggered by government decisions on hydrogen heating or blending
- HSE Policy Re-opener: triggered by changes to HSE requirements (eg post-IMRRP approach)
- Tier 2A Mains and Services Volume Driver: automatic adjustment for non-Tier 1 replacement volumes
- Complex Distribution Systems Re-opener: for emerging work on multiple-occupancy buildings
- Decarbonisation Project Development UIOLI: 0.5% of baseline totex per GDN for small projects
- Small Decarbonisation Projects Re-opener: for larger decarbonisation projects (GBP 1m-100m)
- Decarbonisation and Environmental Policy Re-opener: Authority-triggered for major policy changes
Cross-sector mechanisms also apply: RPE indexation for labour and materials; cost of equity and debt indexation; cyber resilience re-opener; digitalisation re-opener; and the Co-ordinated Adjustment Mechanism for transferring activities between networks.
Gas future and depreciation
Ofgem does not expect large-scale changes to gas networks during RIIO-3 (Overview, para 2.3). However, the government's June 2025 Gas Update to Market identified three strategic challenges: supply resilience, investment-affordability balance, and managing an orderly transition.
New asset depreciation is accelerated using a sum-of-digits method with asset lives set to reach zero by the 2050 net zero target. This adds approximately GBP 10/year to household bills but limits RAV growth and protects future consumers. Existing RAV depreciation is unchanged (Overview 7.4-7.7).
Ofgem reserves the right to adjust depreciation during RIIO-3 based on the government's upcoming call for evidence on network cost recovery, which will explore alternatives to accelerated depreciation for a shrinking gas consumer base (Overview 7.12-7.14).
Cost assessment
Ofgem uses a top-down econometric regression model to benchmark GDN totex, supplemented by non-regression analysis for specific cost categories and technical assessment for bespoke costs. The final efficient totex for the sector is GBP 25.7bn, 12% below GDN submissions (GD Annex Table 46). The 50% TIM sharing factor means GDNs retain half of any over- or underspend against allowances.
Defined terms
See the full defined terms register in the source file.
Cross-references
- Gas Act 1986 -- legal basis for Gas Transporter licences
- Gas Transporter Licence Standard Conditions -- being modified for RIIO-GD3 (statutory consultation Dec 2025)
- RIIO-3 Finance Annex -- cost of capital, debt, depreciation, RAV
- RIIO-3 SSMD GD Annex (July 2024) -- methodology framework
- HSE Iron Mains Risk Reduction Programme -- drives majority of repex
- NESO Regional Energy Strategic Plans -- distribution transition planning
- Government Midstream Gas System Update (June 2025) -- future of gas context
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