G99 DNO Application Timeline for FE College Solar Projects
What FE college estates teams need to know about G99 grid connection applications, DNO timelines, and managing parallel-track project delivery.
Published 9 May 2026 by SEO Dons Editorial
The single most common cause of FE college solar project slippage is the G99 DNO grid connection application timeline. Most estates teams underestimate it. Here’s what to plan for.
What G99 is
G99 is the Energy Networks Association engineering recommendation governing grid connection of distributed generation above 17 kW per phase. Almost every FE college solar install above 50 kW total system size triggers G99 — which means almost every FE solar project needs a DNO application.
Each Distribution Network Operator (DNO) — Northern Powergrid in the North East, Electricity North West in NW England, ENWL across Yorkshire, NPg in Yorkshire and the East Midlands, UK Power Networks across East and South East, SSEN across Central Southern England, Western Power Distribution across the Midlands and South West, ScottishPower Energy Networks in Central and Southern Scotland, SP Manweb in North Wales and Cheshire — has its own G99 application process, fee structure, and typical turnaround.
Typical turnaround timelines
DNO processing varies but typical turnarounds in 2026:
- G98 (sub-17 kW per phase, very small installs): 2-4 weeks
- G99 simple, sub-50 kW total: 6-10 weeks
- G99 moderate, 50-200 kW: 10-14 weeks
- G99 large, 200-500 kW: 14-18 weeks
- G99 very large, 500 kW+: 16-22 weeks (sometimes longer where the DNO requests a Network Study)
Multi-site portfolio applications (FE group corp programmes) can sometimes be batch-processed by the same DNO — coordinating multiple applications with a single point of contact saves time but doesn’t reduce the per-site DNO processing minimum.
Why DNO timeline drives project slippage
The DNO timeline is the single longest-lead item in most FE solar projects. If your structural survey takes 3 weeks, your Salix application takes 8 weeks, your panel manufacture lead time is 6 weeks, but your G99 application takes 16 weeks — the DNO timeline determines everything.
Project managers who underestimate this end up with scaffold up, panels on site, and no commissioning capability because the DNO connection isn’t ready. We’ve seen FE projects sit at 95% complete for 6-8 weeks waiting for the DNO to issue the final connection agreement.
How to manage the G99 application
Three principles for FE college estates teams:
1. Start the G99 application as early as possible
The application doesn’t need a final detailed design — it needs the inverter specification, total kW capacity, point-of-connection location, and proposed connection date. We typically submit G99 within 2-3 weeks of project kickoff, in parallel with structural survey and Salix application preparation.
2. Use a competent DNO liaison
The DNO process is rules-heavy and varies by network. A specialist liaison who understands the relevant DNO’s typical clarification requests, scoring criteria, and timeline expectations dramatically reduces back-and-forth. We provide this as part of every project.
3. Plan installation around the DNO timeline, not vice versa
Most FE estates teams plan installation around the academic calendar (summer break, half-term) and assume the DNO will fit. It’s the wrong way round. Plan installation 2-3 weeks AFTER the expected G99 connection date, allowing buffer for DNO delay. If you can flex install dates by 2-4 weeks based on actual G99 progress, you avoid the “scaffold-up-no-commissioning” trap.
Common DNO clarification requests
The most common clarification requests from DNOs that slow applications:
- Network reinforcement assessment. For larger installs on weaker network sections, the DNO may need to assess whether voltage rise constrains the connection. Adds 3-6 weeks.
- Network Study. For installs above 500 kW on some networks, a full Network Study is required to confirm the connection. Adds 4-8 weeks plus a Network Study fee (£3,000-£15,000 typically).
- Export limitation requirements. Some DNOs require export-limited operation where the connection cannot accept full export. This affects inverter configuration and slightly reduces the project value, but doesn’t delay the connection.
- Single-line diagram clarifications. Small clarifications on the electrical design package — usually resolved in 1-2 weeks.
G99 fees
DNO G99 application fees vary:
- Application fee: £200-£500 typically
- Network Study fee (where required): £3,000-£15,000
- Connection agreement fee: £500-£2,000
- Network reinforcement cost (where required): Highly variable — sometimes zero, sometimes £10,000-£100,000+ for cable upgrades or substation reinforcement
For most FE college projects under 500 kW, total G99-related fees are £500-£3,000. For larger projects requiring Network Study or reinforcement, fees can be significantly higher — and these need to be modelled into the Salix bid up front.
What happens after the connection is approved
Once the DNO issues the connection agreement, the project can proceed to commissioning:
- DNO witness testing. The DNO physically attends commissioning to verify the protection settings and the import/export metering operation. Usually a single day; scheduled 2-4 weeks after connection agreement.
- MCS commissioning certificate. The MCS-certified installer issues the commissioning certificate confirming the installation meets MIS 3002 (commercial PV) standards. Triggers the Smart Export Guarantee registration.
- Smart Export Guarantee registration. The corporation registers with their chosen SEG licensee (Octopus Outgoing, E.ON Next Export Exclusive, etc.) for export tariff payments.
From DNO connection agreement to first commissioning is typically 4-8 weeks. After that the asset is fully operational and generating against the Salix repayment schedule.