Direction to NESO on CSNP publication timing

What changed

Ofgem has directed NESO to delay the first Centralised Strategic Network Plan by 12 months. The submission deadline moves from 30 June 2027 to 15 September 2028; the publication deadline moves from 31 December 2027 to 15 December 2028. NESO requested the derogation itself, writing to Ofgem on 23 March 2026. Ofgem granted it on 15 April 2026, modifying NESO's ESO and GSO licence conditions to accommodate the new dates.

The stated reason is alignment with the revised Strategic Spatial Energy Plan timeline. The SSEP is the spatial input that tells the CSNP where generation and demand will sit; without it, NESO cannot plan the networks to connect them. The SSEP slipped first, and the CSNP has now followed.

What this means in practice

The CSNP is supposed to be the coordinating document for electricity, gas, and hydrogen network investment over a 25-year horizon. It is the mechanism through which transmission investment decisions stop being reactive and start being planned. Without it, network investment continues on the current basis: individual needs cases assessed in isolation, no coordinated view of where capacity should be built, and no framework for sequencing reinforcement against anticipated demand.

The practical consequences fall on three groups:

Developers waiting for grid connections. The CSNP was expected to provide the strategic framework that justifies anticipatory investment — building network capacity ahead of confirmed demand. Every month without that framework is another month where NESO and transmission owners lack the planning basis to invest ahead of need. The connection queue, already measured in years, does not shorten while the strategic plan is delayed. Projects with grid connection dates in the late 2020s are carrying costs — land options, planning consents, financing commitments — that compound with every month of delay. A 12-month slip in the CSNP does not mechanically add 12 months to every connection date, but it removes the planning instrument that was supposed to accelerate the queue.

Transmission owners (NGET, SPT, SSEN-T). These companies need the CSNP to underpin their investment programmes. RIIO-T2 runs to 2026, and the ET3 price control is being set now. The absence of a CSNP during the ET3 determination period means Ofgem is setting a five-year transmission price control without the 25-year strategic plan that is supposed to inform it. Transmission companies will submit business plans based on needs cases they can justify individually, not on a coordinated network strategy. The risk is that ET3 either underinvests (because individual needs cases cannot capture system-wide benefits) or overinvests in the wrong places (because there is no spatial plan to guide where capacity is most needed).

Consumers. Uncoordinated network investment is more expensive than coordinated investment. Building a transmission link to serve one project, then reinforcing it two years later to serve three more, costs more than building it right the first time. The CSNP exists precisely to avoid this. Its delay means the window of uncoordinated investment extends by another year, and the excess cost eventually lands in TNUoS charges.

There is a deeper structural point. NESO requested this derogation. It was not imposed. The system operator concluded that it could not produce a credible CSNP without the SSEP as an input, which is a reasonable technical judgment. But it also reveals the dependency chain: DESNZ produces the SSEP, NESO uses it to produce the CSNP, Ofgem uses the CSNP to assess transmission investment, and transmission owners use Ofgem's approvals to build. A 12-month delay at the top of the chain cascades. The SSEP was already late. The CSNP is now late. The investment decisions that depend on the CSNP are deferred by implication.

What happens next

The revised timeline has three dates that matter:

- SSEP publication: Must now arrive far enough ahead of September 2028 for NESO to use it as an input. The exact SSEP date has not been confirmed publicly, but the CSNP delay implies DESNZ does not expect to deliver a final SSEP before mid-2027 at the earliest. - 15 September 2028: NESO submits the first CSNP to Ofgem for approval. - 15 December 2028: NESO publishes the approved CSNP.

Between now and then, NESO will continue developing the CSNP methodology, running stakeholder engagement, and building the analytical framework. The three-month window between submission and publication (September to December 2028) is Ofgem's review and approval period.

The RIIO-ET3 determination will proceed in parallel. Ofgem will need to set a transmission price control for 2026-2031 without the CSNP that was supposed to inform long-term network needs. This creates pressure either to build flexibility into ET3 (uncertainty mechanisms, reopeners) or to accept that the first years of ET3 will be planned on the old basis.

Watch the SSEP timeline. If the SSEP slips again, the CSNP slips again. The dependency is explicit and acknowledged. The question is whether DESNZ can hold its own deadline when the planning framework it depends on — local authority engagement, spatial analysis, cross-vector modelling — faces the same institutional capacity constraints that delayed it the first time.