What information does the G99 application require?
The G99 application form (available from your DNO portal — UKPN Portal, WPD/National Grid Portal, Northern Powergrid Portal, ENW Portal, SP Energy Networks Portal, SSEN Portal) requires: (1) Site address and MPAN number. (2) Proposed generator type (PV) and technology (inverter-based). (3) Total installed capacity in kW per phase and aggregate. (4) Proposed point of connection — usually the existing LV main switchboard or dedicated solar switchboard. (5) Single-line diagram showing connection arrangement. (6) Inverter manufacturer and model data sheet. (7) Protection relay settings schedule. (8) Anti-islanding confirmation. We produce the complete G99 application pack as part of our design stage — ready to submit immediately after structural survey.
G99 application step by step
Step 1: Pre-application capacity check (1-2 weeks). Run an informal capacity check with DNO — most offer online tools or informal email enquiry. Identifies obviously constrained substations before formal application costs. Step 2: G99 application submission (week 2-4). Submit completed application form + technical pack + application fee (typically £500-£2,500). DNO issues acknowledgement within 5 working days. Step 3: DNO technical study (65 working days statutory). DNO assesses impact on local network. If network is constrained, study may require a full load flow analysis from their network planning team. Step 4: Connection offer (week 16-20 typically). DNO issues Section 16 offer stating connection cost, works scope, and programme. You have 90 days to accept. Step 5: Connection works (6-14 months). DNO builds any necessary network reinforcement. Final Step: G99 commissioning and Protection Settings Test. Total typical timeline: 9-18 months first application to energised.
DNO regional comparison
UK Power Networks (London, SE, East): 4-8 months typical, online portal application. Western Power Distribution / National Grid ED (Midlands, SW, Wales): 6-12 months, well-resourced study team. Northern Powergrid (Yorkshire, NE): 5-10 months, online portal. Electricity North West (NW): 5-10 months. SP Energy Networks (Scotland Central, Merseyside, NW Wales): 5-10 months. SSEN (Scotland N, S England rural): 6-14 months, most constrained capacity in southern rural areas. NIE Networks (Northern Ireland): 8-16 months. Capacity constraints are most acute in southern England (UKPN and SSEN south) due to high renewable penetration on distribution networks.
When grid reinforcement is needed
Sites with capacity headroom on existing connection: minimal DNO fees (£2-10k connection works). Sites requiring grid reinforcement: £25k-£500k+ for contestable connection works — includes substation upgrades, new cable routes, transformer uprating. Constrained substations are increasingly common in southern UK and some northern rural areas. We run a pre-application capacity check during structural survey — if constraint is likely, we model the connection cost into the project economics before proceeding to formal application.
Optimising the G99 timeline
Submit G99 immediately after structural survey to start the clock. Run DNO process in parallel with planning permission (where required), lease consent, roof warranty consent, and insurer review — these parallel workstreams are not on the critical path if G99 is submitted first. For systems above 1 MW, expect 9-14 months total connection timeline. The application fee is non-refundable but the connection cost in the offer can be challenged via the DNO dispute process if it appears excessive.
Common questions
How do I submit a G99 application for warehouse solar?
Each DNO has its own portal and application form. UKPN: ukpowernetworks.co.uk portal. National Grid ED (formerly WPD): nationalgrid.co.uk. Northern Powergrid: northernpowergrid.com. Electricity North West: enwl.co.uk. SSEN: ssen.co.uk. We produce the complete G99 application pack — single-line diagram, inverter data sheets, protection schedule — as part of our design stage deliverable and submit on your behalf.
How long does a G99 application take to process?
DNOs have a statutory 65 working day (13 week) target for the technical study from acknowledgement of a complete application. In practice: straightforward connections in unconstrained areas complete in 10-12 weeks. Complex connections requiring load flow analysis from network planning can take 18-22 weeks before offer. We submit G99 immediately after structural survey so the study runs in parallel with all other project stages.
How long does G99 take in the UK from application to energised?
9-18 months total typical, depending on DNO region and grid capacity. Technical study 65 working days (3 months). Connection works 6-14 months. We submit G99 immediately after structural survey to start the clock and minimise the overall project timeline.
How much does G99 grid connection cost?
£2-10k for sites with capacity headroom on existing infrastructure (most modern industrial estate). £25-500k+ where grid reinforcement is required (substation upgrade, new cable route, transformer uprating). Pre-application capacity check during structural survey identifies constraints early — we model connection cost into project economics before committing to formal application.