TMO4+ Explained: What UK Grid Connection Reform Means for Factory Solar
On 15 April 2025 Ofgem approved TMO4+ — the biggest overhaul of UK grid connection policy in two decades. First Ready and Needed, First Connected replaces the first-come-first-served queue. Here is the practical impact on factory solar, G99 applications and co-located BESS projects — updated for April 2026.
What TMO4+ Actually Does
Before TMO4+, over 700 GW of speculative generation projects sat in a congested UK connection queue — many with no land rights, consents or funding. New solar and BESS developers routinely faced 10-15 year connection offers, blocking shovel-ready projects including factory rooftop schemes above 1 MW.
TMO4+ replaces the queue with a two-gate system managed by NESO (for transmission) and DNOs (for distribution):
- Gate 1: Indicative connection, no firm date. Low evidence requirements.
- Gate 2: Firm connection date, Ready and Needed status required. Applicant must demonstrate land rights, planning progress, commercial readiness and alignment with the Strategic Spatial Energy Plan.
NESO's November 2025 Connections Reform action plan removed around 400 GW of non-progressing queue positions, freeing headroom at transmission and grid supply points.
Does TMO4+ Affect Your Factory Solar Project?
Most typical factory rooftop systems are not affected by the worst of TMO4+. If your project is under 1 MW and connects at low or high voltage via a G99 application to your DNO, you are not in the transmission queue and your timelines are set by your DNO's local process.
Projects that are reshaped by TMO4+:
- Co-located BESS above 5 MW on the same connection point
- Rooftop PV and carport combined projects above 10 MW exporting to grid
- Private wire PPAs drawing residual supply from a new grid connection point
- Ground-mount solar on adjacent land being exported at 11 kV or 33 kV
Practical Impact on Factory G99 Applications
Under 1 MW rooftop
No direct impact. DNO G99 process unchanged. Typical timelines 8-16 weeks depending on DNO. Export limitation may still apply at constrained nodes.
1-5 MW rooftop or rooftop + BESS
Added evidence requirements at the DNO under Gate 1 submissions. Land rights, planning advice and commercial readiness documentation required. Timelines 14-26 weeks.
5-10 MW solar + BESS hybrid
Full Gate 1 / Gate 2 process. Strategic Spatial Energy Plan alignment test applies. Expect 26-52 weeks to firm connection offer. Queue-jumping possible via Ready and Needed status.
Private wire PPA
Private wire routes within the 2 km rule can bypass much of TMO4+ because the transmission connection is not modified. Popular for logistics parks and multi-tenant industrial estates.
DNO Timeline Snapshot (April 2026)
| DNO Area | Typical G99 Timeline | Typical Fee Band |
|---|---|---|
| UK Power Networks — Eastern | 8-16 weeks | £3,500-£12,000 |
| UK Power Networks — London | 10-20 weeks | £4,000-£15,000 |
| National Grid Electricity Distribution | 6-14 weeks | £3,000-£10,000 |
| SP Energy Networks | 8-16 weeks | £3,500-£11,000 |
| Scottish & Southern (SSEN) | 8-24 weeks | £3,500-£14,000 |
| Electricity North West | 8-18 weeks | £3,500-£12,000 |
| Northern Powergrid | 6-14 weeks | £3,000-£10,000 |
Frequently Asked Questions
Does TMO4+ affect rooftop solar at my factory?
G99 connections under 1 MW are generally outside the worst of the queue backlog. TMO4+ mainly reshapes large transmission and co-located BESS above 5 MW, but smaller rooftop projects still benefit from the clearer Gate 1/Gate 2 process.
What is First Ready, First Connected?
TMO4+ replaces the old first come, first served queue with a two-gate system. Only projects that are Ready (land, funding, consents) and Needed (aligned with the Strategic Spatial Energy Plan) proceed to Gate 2 and a firm connection date.
When did TMO4+ take effect?
Ofgem approved TMO4+ on 15 April 2025 and NESO launched the new process in late 2025. DNOs rolled out equivalent distribution-level reforms through early 2026.
Will my G99 timeline be longer or shorter under TMO4+?
For typical factory rooftop systems (under 1 MW), timelines are unchanged or slightly faster because the new rules free DNO capacity previously committed to speculative projects. Larger projects with co-located BESS may see added discipline and evidence requirements.
Related Reading
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