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The Eastern Green Link series and ASTI — Scottish generation to English demand.
Scotland produces materially more renewable generation than it can consume; England consumes materially more than it produces. The onshore Scotland-to-England transmission corridors are constrained. The Eastern Green Link series provides subsea HVDC links that bypass that constraint — four links of 2 GW each, 8 GW combined nameplate, with a fifth in early scoping.
Five observations stand out: EGL1 and EGL2 are in construction — the programme has passed the regulatory hurdle; EGL3, EGL4 and GWNC secured early-investment approval in December 2025 — three superhighways, not two; the technology is standardised at 525 kV VSC across the series; ASTI is the procurement accelerator now informing RIIO-T3; and the operational delivery test is now in flight.
The consequence: the regulatory and investment-commitment work is largely complete for EGL1–EGL4, but the binding constraints on the Q3 2028 picture are now operational — cable factory capacity, vessel availability, converter-station construction and multi-jurisdictional consenting.
EGL1 received Ofgem approval in December 2022 and began construction in February 2025; EGL2 received final approval in August 2024 and targets energisation in 2029. EGL3 and EGL4 secured early-investment approval in December 2025 with DCO applications due to the Planning Inspectorate in 2026 and target operations of August 2034. The £3.4 bn 2022 estimate for EGL1+EGL2 is now £5.594 bn actual.
The EGL series is the backbone reinforcement that connects ScotWind and Scottish onshore wind to English demand. Without it, the Connections Reform pipeline (Gap 15) can issue Gate 2 offers for Scottish projects that cannot physically deliver. The NESO Cost Benefit Analysis values the redesigned EGL3/EGL4/GWNC package at £3–6 bn of consumer benefit versus the original network design.
The shape of this volume. Section 1 sets out the EGL headline figures. Section 2 develops twelve findings, each confidence-annotated. A chapter-weight pull at p. 14 anchors the argument. Section 3 decodes the transmission architecture. Section 4 steps through EGL1–EGL5 project-by-project. Section 5 decodes the ASTI framework and RIIO-T3. Section 6 sets out recommendations, with a one-page tear-out at p. 25.
EGL1 + EGL2 in construction; EGL3 + EGL4 + GWNC approved Dec 2025; EGL2 targets 2029, GWNC December 2033, EGL3 + EGL4 August 2034. EGL1 offshore installation runs ~2 years late at 2027–2028.
Navy blocks mark approvals and targets; the ink blocks are the Dec 2025 ASTI anchor and the Aug 2034 destination. The EGL1 offshore delay is flagged at MEDIUM confidence.
HIGH — anchored to a verified Ofgem or transmission-owner published position. MEDIUM — Ofgem / NESO direction of travel with material implementation questions open. LOW — GridteamAI inference where the source supports direction but not magnitude or pacing.
Findings 01 – 12 · summary
Findings 01 – 09 follow in detail · pp. 10 – 12 · 10 – 12 carried on the Section 6 matrix
EGL1 received Ofgem approval in December 2022 under ASTI, with construction commencing 13 February 2025; EGL2 received final approval in August 2024 and began construction in September 2024, targeting energisation in 2029. EGL1’s offshore construction is delayed by ~2 years, with cable installation now scheduled 2027–2028. The structural significance is that the programme has cleared the regulatory hurdle and is in the operational delivery phase — Q3 2028 status turns on execution, not further regulatory decisions.
Ofgem's December 2025 decision approved early construction funding for three schemes — EGL3 (8% of updated forecast cost), EGL4 (13%) and the Grimsby West–Norfolk Connection, a separate 75-mile 400 kV onshore link. National Grid, SSE and Scottish Power invest in the two subsea cables; both terminate at Anderby Creek, Lincolnshire. Target operations are August 2034 for EGL3/EGL4 and December 2033 for GWNC. DCO applications are due to the Planning Inspectorate in 2026.
EGL1, EGL2, EGL3 and EGL4 are each rated 2 GW (bi-pole), 525 kV DC, using Voltage Source Converter (VSC) technology on Cross-Linked Polyethylene (XLPE) cables, with mass-impregnated (MI) as fall-back — one technology platform across 8 GW of nameplate. Standardisation lowers supply-chain risk, lets operational capability accumulate across the fleet, and underwrites UK domestic supply-chain investment that pays back over multiple schemes plus EGL5 and beyond.