Connections

Seven hundred gigawatts waiting on a 55-gigawatt system, and the reform re-sorting the queue.

The GB connection queue holds more than 700 GW of generation and storage against a system with 55 GW winter peak demand. Most of those projects will not be built. The 2025 TM04+ reform introduces a two-gate readiness process that re-sorts who holds a place. This route traces the problem, the reform, and the practical connection routes today.

12Route 12 of 12 · Operations and networks
13 min read 4 sections 1 diagram 1 decision tool Last verified

After this route you will be able to

  • Explain how the GB connection queue grew to its current size.
  • Describe the TM04+ two-gate readiness process.
  • Distinguish transmission from distribution connections, and which body signs off each.
  • Identify what a flexible connection is and where it is now standard.
  • Make a reasoned call on a project-level connection strategy.
Grid Supply Point substation where new generation connects to the transmission system

25 April 2025Ofgem approves TM04+ · two-gate readiness reform goes live

Ofgem approved the largest single reform of GB connections in a generation. A ten-year problem reshaped in a single decision.

On 25 April 2025, Ofgem approved CUSC Modification 434 (TM04+). The reform re-sorts the 700+ GW connection queue through a two-gate process, requires projects to demonstrate readiness on land rights, planning consent and financing, and gives priority to projects aligned with Clean Power 2030.

The queue had grown from around 75 GW in 2020 to over 700 GW by 2024. Under the old first-come, first-served regime, any project that paid a small fee could hold its place indefinitely. The network assumed all queue members were real when calculating reinforcement needs, which delayed actual projects behind phantom ones.

Implementation is now running through 2025 and 2026. Every project in the queue receives a readiness assessment. Projects that do not pass move to a slower track. Projects that do pass and align with Clean Power 2030 can accelerate. By 2027, the queue is expected to reduce by 40-60 percent through re-sorting and withdrawal.

The reform re-sorts the queue. It does not add physical capacity. What is the right long-run balance between queue discipline, network reinforcement, and flexible connection use?

The answer depends on understanding how connection authority splits. Transmission connections go through NESO. Distribution connections go through the local DNO. Each has different process, different cost, different timeline.

Section 01 · How connections work

Transmission via NESO. Distribution via the DNO. Different processes, same physical grid.

The connection process depends on the voltage level at which a project connects. Above roughly 132 kV, NESO is the counterparty. Below, the local DNO (transitioning to DSO) is.

Diagram 01 · GB connection pathways

The queue dwarfs realistic need. TM04+ is designed to reduce the queue to projects that can demonstrate they will actually build and connect within a credible timeframe.

Transmission connections (≥132 kV entry, or large projects including offshore wind farms). Applicant submits to NESO, who models the network impact, offers a date for a full technical acceptance, requires payment of a security bond. Timeline from application to first power: 5-15 years. Cost of the connection works: £5m-£500m+ depending on scale.

Distribution connections (<132 kV, or embedded generation). Applicant applies to the local DNO. DNO models the constraint, offers a connection date, quotes the reinforcement cost. Timeline 6-36 months for smaller projects; up to 7 years for large battery or solar projects. Cost typically £100k-£20m.

Flexible connections are available in both tiers. The connection is accepted but with an agreement that the network operator can curtail output at times of constraint. Many grid-scale batteries in England operate on flexible connections today.

Section 02 · TM04+

Two gates. Readiness, alignment, and a slower track for the rest.

TM04+ restructures the queue around two assessment gates. The mechanics matter because they determine which projects deliver by 2030 and which slip to 2035+.

Gate 1 (Readiness). Every queued project must demonstrate land rights (option or ownership), planning progress (at least application submitted), and financing progress (letter of intent, term sheet or confirmed funding). Projects failing Gate 1 slip to a slower track.

Gate 2 (Alignment). Projects passing Gate 1 are further categorised by alignment with the Clean Power 2030 Action Plan. CP2030-aligned projects receive priority treatment for connection dates and capacity allocation.

Projects failing either gate are not cancelled. They move to a slower track where they can still secure a connection date, but behind all Gate 2 projects and subject to rolling readiness reviews.

The effect is that speculative projects and those not aligned with government strategy face a longer wait. Projects that are ready and aligned can accelerate. The queue is re-sorted rather than shortened, which is the correct mechanism given that many queue entries were real-but-late rather than never-going-to-happen.

Connection applicants must satisfy the readiness criteria on land rights, planning consent and financing set out in CMP434. Projects not meeting these criteria by the relevant assessment date will be moved to a slower track, retaining their right to connect but without priority queue treatment.

CUSC Modification CMP434 (TM04+), Ofgem approval April 2025

Section 03 · Project strategy

Firm offer, flexible offer, or locate differently?

A developer facing a long firm-connection date has three choices. Each trades speed against cost and against output value.

No option is wrong. The decision depends on capital structure and site economics. Wait for firm 2032. Maximise output value. Accept flexible 2028. Start earning sooner. Relocate to a less-constrained node. This is the right answer for large utility-scale wind, where the output is CfD-indexed and the project economics need full capacity. Start over This is increasingly the right answer for grid-scale batteries and merchant solar. Curtailment is rarely as bad as worst-case models predict. Start over This is the locational-marginal-pricing case in practice: send the developer somewhere the grid has headroom, even if generation conditions are slightly worse. Start over

Check your understanding

Three questions on what you have just read.

Paying a security bond Land, planning and financing readiness Construction-ready status Being awarded a CfD NESO The local transmission owner The local DNO Ofgem A connection with a movable date An interconnector connection Network can curtail output at constrained times A flexible tariff

Key takeaways

  • The queue is 700+ GW against a 55 GW peak system. Most queue entries will not build.
  • TM04+ re-sorts the queue with two gates: readiness, then CP2030 alignment.
  • Transmission connections go through NESO. Distribution via DNO. Different timelines, different costs.
  • Flexible connections trade maximum output for faster connection. Many 2025 grid-scale batteries operate this way.
  • The reform is working through 2025-26. Expected queue reduction of 40-60 percent by 2027.

References

  1. Ofgem: CMP434 TM04+ decision

    Two-gate readiness process, approval April 2025.

    Primary regulatory reference.

  2. NESO: Connecting to the network

    Application process, queue statistics, connection offer mechanics.

    Primary process source.

  3. DESNZ: Clean Power 2030 Action Plan

    Strategic alignment criteria referenced by Gate 2.

    Policy anchor.

  4. NESO: Connection and Use of System Code (CUSC)

    Home of the modification process for connection reform.

    Code authority.

The next route covers system resilience. What happens when the connections, voltage, and balancing layers are all stressed at once.