The statutory window for a DNO to return a G99 connection offer is 45 working days, but in 2026 real-world timelines run from a few weeks for small, simple sites to 4 to 6 months for most commercial projects, and considerably longer where network reinforcement or Gate 2 clearance under Ofgem's TMO4+ reform is required.
Introduction
The G99 connection offer determines when a project can be built, how much it will cost, and whether it can secure a grid connection at all. In 2026, the rules are shifting alongside Ofgem's wider connections reform, and timelines vary dramatically between projects, DNOs, and network regions. This article sets out what developers can realistically expect from a G99 application in 2026, drawing on Ofgem performance data and the operational impact of the TMO4+ reform.
The 45-working-day window vs. reality
The 45-working-day statutory window applies to the connection offer stage only, not the full end-to-end process. The clock starts when the DNO accepts the application as complete and stops when the offer is issued. It does not cover the pre-application enquiry, the developer's acceptance window, or the period between offer acceptance and energisation.
End-to-end timelines depend on project type, network condition, and queue position. The 45-day figure is the floor for a clean, well-prepared application on an uncongested part of the network. It is not a reliable forecast for projects requiring reinforcement, transmission impact assessment, or Gate 2 clearance.
Indicative 2026 timelines by project type
Realistic 2026 ranges for the connection-offer stage are as follows:
- G99 Fastest Option (small Type A with export limiting under 32A): 2 to 4 weeks
- Type A, no reinforcement: 6 to 10 weeks
- Type A or B with minor reinforcement: 3 to 6 months
- Type B or C requiring substation reinforcement: approximately 6 to 12 months
- Type C or D requiring transmission interaction: 12 months or more, plus Gate 2 clearance
Increasingly, even distribution-connected projects are subject to transmission impact assessment (TIA), particularly in constrained regions, adding further uncertainty to timelines.
Real-world reports from 2025 and 2026 show offer times stretching from a few weeks to over six months even on small commercial sites, with demand and queue backlog cited as the main drivers (Green Shield Group, 2025). Energisation is a separate matter: for Type B and above projects, the gap between offer acceptance and energisation is typically 12 to 36 months, dominated by substation reinforcement works.
Connection performance by DNO: what the Ofgem data shows
Ofgem does not publish a single "G99 wait time" league table. The connections data in the RIIO-ED2 annual reports covers all metered connections, predominantly domestic and small-commercial low-voltage jobs, rather than generation-only volumes. It is the best available proxy for DNO connection performance, and the trends broadly align with developer experience reported across the market.
Three indicators from the Ofgem RIIO-2 Electricity Distribution Annual Report 2024 to 2025 are most relevant (Ofgem, 2026).
Connection Guaranteed Standards (GSoP) failure rate, 2024-25
This is the percentage of cases where the DNO missed the statutory minimum.
| DNO Group | GSoP failure rate, 2024-25 |
|---|---|
| UK Power Networks | 0.02% |
| Electricity North West | 0.16% |
| NGED | 0.48% |
| SP Energy Networks | 0.93% |
| Northern Powergrid | 1.77% |
| SSEN | 3.23% (SSES 4.11%) |
Major Connections Incentive (MCI): customer satisfaction, 2024-25
Industry average was 8.72 out of 10. UK Power Networks (London Power Networks licence area) and SP Distribution scored above 9.0. SSEN's southern licence area (SSES) was lowest at 7.92.
Time to Connect (TTC): Year 2 ranking
Ranked best to worst by reward earned: Electricity North West, UK Power Networks, SSEN, SP Energy Networks, NGED, Northern Powergrid.
Two cautions apply. TTC and GSoP are weighted toward smaller LV connections, so a top-ranked DNO is not automatically the fastest on a Type B G99 application. And none of these metrics capture time to first G99 offer, which is the figure most generation applicants actually want. Ofgem has committed to making this kind of data more transparent under the connections reform package (Ofgem, 2025).
Each DNO also publishes a Major Connections Annual Report (MCAR) under RIIO-ED2. These break out customer satisfaction (MCCSS), time to quote (MCTTQ) and time to connect (MCTTC) by "Relevant Market Segment" including Distributed Generation, and are the closest thing to a G99-specific scorecard currently in the public domain. None split performance by G99 Type A/B/C/D, but they are the best per-DNO source.
What changes under 2026 connections reform
The biggest 2026 change is the integration of distribution applications into Ofgem's TMO4+ connections reform, approved in April 2025 and operationalised by the National Energy System Operator (NESO) through 2026 (Ofgem, 2025). Gate 1 offers are non-binding and indicative; Gate 2 offers are firm but only awarded to projects meeting readiness and strategic-need criteria.
NESO's published timeline schedules Gate 2 Phase 1 distribution offers between July and mid-November 2026, with Phase 2 distribution offers running from mid-October 2026 into March 2027 (NESO, 2026). Projects without land rights, planning progress, or grid-need alignment will not receive a firm Gate 2 offer in this window.
The reform is designed to clear the backlog. NESO has re-ordered the 722GW gross queue to prioritise 381.5GW of ready-to-build capacity (NESO, 2026). The trade-off is that speculative applications now face longer waits than the 45-day figure suggests, while well-prepared projects move through faster.
How site quality drives timeline
Most G99 delays are not caused by the DNO assessment itself but by the upstream work: choosing a site with sufficient grid headroom, identifying the correct point of connection, and screening out sites where reinforcement will be prohibitive. Under TMO4+, this matters more than ever because Gate 2 readiness criteria explicitly reward projects with mature site selection.
Feasibly compresses the pre-application screening into minutes by pulling live data from all UK DNOs alongside planning and geospatial datasets, accessible via natural language. For commercial developers, this means a better-targeted G99 application with a higher chance of an acceptable offer and a faster route through Gate 2. For community energy groups, it means the feasibility check that historically priced them out becomes affordable.
Conclusion
In 2026, a G99 application is both more important and more variable than at any point since the standard's introduction. The 45-working-day statutory offer window remains, but real timelines are governed by project type, network condition, and the Gate 2 readiness threshold under TMO4+ reform. Developers who pre-screen sites carefully will move through G99 faster, pay less in reinforcement charges, and reach energisation years ahead of those who treat the application as a starting line.