Draft Centralised Strategic Network Plan Guidance

What changed

Ofgem has finalised its guidance for the Centralised Strategic Network Plan. The draft guidance was consulted on in August 2025, the consultation closed on 2 September 2025, and Ofgem published its decision on 17 November 2025 after receiving 21 responses. The guidance sets the rules NESO must follow when it builds the CSNP Methodology, which in turn determines what transmission infrastructure gets recommended for construction across Great Britain.

The CSNP is a single, NESO-produced, long-term plan covering electricity transmission, natural gas transmission, and, for the first time, hydrogen transport and storage. It replaces the previous arrangement under which each transmission owner planned its own network and the system operator coordinated at the margins. The decision document records where stakeholders asked for material changes to the draft and how Ofgem responded; it is designed to be read alongside the finalised guidance rather than as a standalone instrument. The guidance is "largely aligned" with Ofgem's 2023 CSNP policy decision, with Ofgem flagging the points where it departed and giving reasons.

What this means in practice

The substance of the CSNP is not in this guidance; it is in the methodology NESO writes against it. Ofgem made a deliberate choice to wait for NESO to develop its approach before pinning down requirements, so that NESO could "explore potential approaches without being overly limited by pre-set requirements." That sequencing matters. The body that runs the system, connects generators, and advises on network need is also the body designing the rules that decide which networks get built. The guidance is the only external constraint on that methodology, and it is written at the level of expectations rather than hard tests. Whoever owns the methodology owns the answers; the discipline on NESO is procedural, not a binding cost test that forces the plan to justify each reinforcement against the cost it imposes on consumers.

For transmission owners, the planning function moves decisively away from them. National Grid Electricity Transmission, SP Transmission, and SSEN Transmission no longer set the strategic shape of their own networks; they build what the centralised plan specifies. This concentrates the build decision in one place. It also concentrates the failure mode: a methodology that systematically over-specifies reinforcement produces over-build across all three onshore electricity TOs at once, and consumers fund it through transmission charges under the RIIO framework. A centralised plan is only as disciplined as the cost test inside its methodology.

The hydrogen inclusion is the most consequential forward signal. Putting hydrogen transport and storage inside a whole-system transmission plan, alongside electricity and gas, formalises hydrogen networks as a regulated transmission asset class in waiting. There is no hydrogen transmission network to plan today. Including it in the CSNP scope creates the planning machinery before the asset exists, which is the standard route by which a new regulated network gets built: define the planning obligation, then the need case follows, then the RAB. Anyone tracking where the next consumer-funded network buildout originates should read this as the planning hook for it.

For generators and developers, the practical consequence is indirect but real. The CSNP determines where reinforcement happens and therefore where connection capacity opens up. A centralised plan with a credible build programme could shorten the path to connection in reinforced corridors; a plan that recommends large strategic reinforcement without a delivery mechanism is a target, not a connection. The test is not the elegance of the plan but whether the reinforcements in it actually get consented and built on the timeline the plan assumes. Delay between plan and delivery is a transfer of value from everyone waiting on the queue to the future.

What happens next

The immediate next step is NESO's CSNP Methodology, developed against this finalised guidance. NESO has been working the methodology with network owners, government, and Ofgem since the 2023 policy decision, so the guidance lands on a methodology already in train rather than starting it from scratch. The methodology is where the substantive consultation fights will be: cost-benefit approach, treatment of optionality and uncertainty, how non-network and behind-the-meter alternatives are weighed against reinforcement, and the basis on which hydrogen need is assessed when no network exists.

Watch for the first CSNP Methodology consultation and then the first CSNP itself. The methodology document is the one to scrutinise line by line: it contains the cost test, the counterfactual treatment, and the assumptions that decide whether the plan disciplines spend or rationalises it. The guidance approved here sets the frame; the methodology fills it, and the first CSNP applies it to actual reinforcement decisions that flow through to RIIO transmission allowances and consumer charges. The hydrogen scope should be tracked separately: any move from "in scope of the plan" to "need case established" is the point at which a new consumer-funded network stops being hypothetical.