UK Grid Web, September 2026
The first verified map of the UK electricity transmission build-out. 48 nodes, 58 flows and 1,347 sourced facts, plus an honest register of what it could not prove.
The first verified map of the UK electricity transmission build-out: what it contains, what it already shows, and what it does not yet hold. This is the initial build. It will be extended from the nodes that matter most.
What the web maps
The web maps the transmission system as a supply chain and as an institution. On the physical side it runs from materials (copper, electrical steel, cable insulation, steel, concrete) through components (transformers, switchgear, HVDC cable and converters, towers, conductor) into the system itself, then down through grid supply points and distribution to the customer. On the institutional side it maps the sequence that has to complete before anything gets built: strategic planning, pre-construction, development consent, regulatory funding approval, the connections process, and construction.
Every node and every flow exists in the web only because a primary document says it does, with the sentence quoted. On top of that structure sit the rules that govern each flow, the companies and public bodies that occupy each position, the commitments that pull demand onto the structure or add capacity to it, and the dated events that show where it has broken or moved. Where something was looked for and not found, the web records the search instead of guessing.
What was created
| Output | Count |
|---|---|
| Verified nodes | 48 |
| Verified flows | 58 |
| Live facts | 1,347 |
| Primary sources | 232 |
| Actors, all with registry identifiers | 45 |
| Instruments | 28 |
| Commitments | 46 |
| Events | 15 |
| Links (actor, rule, commitment and event placements) | 504 |
| Recorded gaps | 405 |
| Retracted facts, kept on the record | 72 |
Of the 1,347 facts, 195 are corroborated by two independent issuers, 8 are derived arithmetically from other facts, and the remainder each rest on a single primary source. Seventy-two facts were retracted during the build and stay on the record with their reasons. The 45 actors range from the three transmission owners, the system operator and the regulator to the factories that make transformers, cable and converters. The 28 instruments are the statutes, licence conditions, codes, standards and regulatory decisions that govern the flows. The 46 commitments are the money and the mandates pointed at the structure: licence delivery obligations, price control allowances, factory expansions, supply frameworks and contracts.
Source: UK electricity grid map, 12 September 2026
Regulator documents (Ofgem, NESO, DESNZ, Companies House, US DOE) and company publications carry most of the evidence. Trade press and academic sources support nothing on their own.
Source: UK electricity grid map, 12 September 2026
Links are facts too: each one carries the sentence that places an actor on a node, a rule on a flow, or a commitment on the structure.
What the map already shows
The programme
Ofgem applied its accelerated framework to 26 onshore transmission projects worth £19.8bn in December 2022 and later designated 17 of them. National Grid Electricity Transmission's licence now sets a delivery date and, for six of them, a public allowance for each one. The RIIO-3 determination adds a £10.7bn baseline for the three transmission owners, £3.5bn for replacing ageing assets and around £4bn for advanced procurement, and is meant to see 80 projects completed within five years, with 3,500 km of new circuits and 4,400 km of overhead line upgraded. NGET's own plan runs to £31bn, of which £4.38bn was delivered in the year to March 2026.
Reset in December 2025 after a material scope change
- 31 December 2028E2DCHWUPOPN23
- 31 December 2029BTNOEDEUPTC1TKRE4
- 31 December 2030PTNOE4D32
- 31 December 2031AENCATNCCGNCEDN2SCD15
- 31 December 2033GWNC1
- 31 August 2034EGL3EGL42
Source: UK electricity grid map, 12 September 2026
EGL3, EGL4 and GWNC were reset in December 2025 after a material scope change. Fourteen of the seventeen allowances are confidential in the licence.
The supply chain
Lead times have moved in one direction. In 2010 a large transformer took five to twelve months from a US producer and six to sixteen from abroad. US producers now report up to and beyond 36 months. An IEA survey puts large transformers at up to four years and says average lead times for transformers and cables have almost doubled since 2021. Ofgem's own statement is 75 percent longer for transformers and 100 percent longer for cables, with HVDC cable often above five years. There is no substitute for a large power transformer, and qualifying a new manufacturer takes several years.
Source: UK electricity grid map, 12 September 2026
The 2010 figures are US market averages; the later figures are upper bounds reported to the US DOE, the IEA and Ofgem.
Demand against capacity
One hundred links in the web record a commitment pulling demand onto a node. Nine record capacity being added. The additions are Siemens Energy's Nuremberg transformer works, up 50 percent by 2028, Hitachi Energy's bushing plant in Tennessee by mid-2027, NKT's cable capacity in 2027, LS Cable's plant in Korea, GE Vernova's Stafford converter site, Painter Brothers' tower steel facility in Hereford by 2028, and Sumitomo Electric's cable factory at Nigg, the only one in Great Britain, where manufacturing has moved from 2026 to the second quarter of 2027. Against that, NKT's high-voltage order backlog stood at €10.2bn at the end of 2025.
Source: UK electricity grid map, 12 September 2026
The layers overlap: allowances, company plans and supply frameworks fund the same works, so they are not added. The allowance layer is incomplete because 18 licence allowances are confidential.
Connections
By September 2023, 549 GW of projects held connection agreements, 406 GW of them at transmission. The queue passed 700 GW before reform. The reformed process has moved 283 GW of generation and storage and 99 GW of demand forward, with 132 GW aligned to the 2030 clean power target, and the next application window opens in the second half of 2026. The stated aim is to cut the average wait from five years to six months. A substation at Uxbridge Moor is being built to connect more than a dozen data centres from 2029.
Events
A fire at North Hyde substation in March 2025 damaged two supergrid transformers and cost £19m to put right; the regulator's investigation is open. The 2021 fire at the IFA1 converter station produced £92m of insurance claims. NGET reports a system access bottleneck, the outages needed to build on a live network. Ofgem approved 89 percent of re-opener funding requests against a 95 percent target. 23,468 kg of SF6 has been removed from switchgear in the first stage of a £109m programme.
The three funding layers do not reconcile, and the web records that as a finding rather than a discrepancy. The £10.7bn baseline covers all three owners' core spending and excludes the accelerated projects. NGET's £31bn spans its whole programme, most of whose project allowances the licence keeps confidential.
What is not yet mapped
- Fourteen ASTI and four other licence allowances are confidential. Their values are recorded as gaps with the search that failed.
- Nineteen nodes have no named occupant, among them the materials, the distribution network beyond one licensee, offshore transmission owners and the demand side. Thirteen distribution licensees and the OFTO register are gaps.
- Two of the world's electrical steel producers, thyssenkrupp and POSCO, are recorded as leads, not actors.
- Eleven physical flows have no governing standard mapped. The institutional side of the web is better instrumented than the physical side.
- No constraint cost figure is held. The cost of Scottish wind curtailed while the corridors are built is the largest number the web does not yet contain.
What comes next
This is the root of the web, not its extent. The next builds start from the nodes the map itself points to: power transformers, where no relief is evidenced and the material chain runs through two named steel producers; HVDC cable and converters, where five makers hold the order books; and the connections process, where 99 GW of demand now sits. Each extension is built and verified to the same standard before it joins. Between builds, the web is re-checked against its sources, and what has changed is published as an update.
Sources
- Ofgem, Electricity Transmission Licence Standard Conditions (August 2026) and National Grid Electricity Transmission plc Special Conditions (September 2026), including the ASTI price control deliverable table.
- Ofgem, RIIO-3 Final Determinations, Electricity Transmission (4 December 2025); press release, 1 July 2025; Decision on accelerating onshore electricity transmission investment (15 December 2022); project assessment decisions for EGL1 (15 November 2024) and EGL2 (13 August 2024); consultation on material scope change for EGL3, EGL4 and GWNC (11 September 2025); call for input on the supply chain (25 March 2026).
- National Grid Electricity Transmission plc, Annual Report and Accounts 2025/26 (approved 22 July 2026); National Grid plc, Annual Report and Accounts 2025/26 (approved 13 May 2026).
- NESO, connections reform results (8 December 2025); DESNZ, Connections Action Plan (22 November 2023) and CfD Allocation Round 7 results (14 January 2026); EN-1 and EN-5 National Policy Statements (December 2025).
- US Department of Energy, Large Power Transformers and the U.S. Electric Grid (2014), Electric grid supply chain review (2022) and large transformer assessment (2024); IEA, Building the Future Transmission Grid (2025); USGS, Mineral Commodity Summaries, Copper (February 2026).
- Company publications: Siemens Energy (5 September 2025), Hitachi Energy (20 August 2025), Sumitomo Electric (14 May 2024, 9 July 2026), NKT Annual Report 2025, Prysmian (30 November 2023, 27 February 2024), Nexans (6 June 2024), GE Vernova (24 September 2024), SSEN Transmission (2023 to 2026), Painter Brothers; Companies House, GLEIF and SEC EDGAR records for every actor.
Every figure above is a promoted fact in the web with its quote and locator; the interactive map carries them by fact id.