How long does a G99 grid connection application take?

Under the Engineering Recommendation G99, Distribution Network Operators (DNOs) must acknowledge a complete application within 10 business days. For straightforward low-voltage connections, a decision is typically issued within 45 calendar days. Complex applications — for example those requiring network reinforcement or high-voltage connections — may take longer and may require a feasibility study.

Do I need a G99 application for a 4kW solar system?

It depends on the inverter export capacity. A 4kWp solar PV system on a single-phase connection typically exports at up to 3.68kW (16A × 230V). If the inverter is configured to export above this threshold, G99 applies. Many 4kWp systems with export limiting set below 16A can use the G98 notification process instead. Confirm the export capacity with your inverter manufacturer and installer.

Which DNOs handle G99 applications in the UK?

The six licensed Distribution Network Operators in Great Britain are: National Grid Electricity Distribution (NGED, covering South West, South Wales, East Midlands, West Midlands), UK Power Networks (London, South East, East of England), Northern Powergrid (North East, Yorkshire), SP Energy Networks (Scotland and North Wales), Electricity North West (North West England), and SSE Networks (South Scotland, North of Scotland). Each DNO has its own application portal and fee schedule for G99 applications.

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G98 and G99 Grid Connection Applications — UK Solar & Generation Guide

Q: What is the difference between G98 and G99?

G98 covers micro-generation systems with an export capacity of up to 16A per phase (typically up to 3.68kW single-phase or 11.04kW three-phase). G99 covers all generation units above this threshold. G98 installations use a simplified notification process; G99 installations require a full application and DNO approval before connection.

A practical guide to G98 notification and G99 application processes for solar PV and other small-scale generation in the UK. Covers which threshold applies, how to submit to your DNO, typical timelines, and how property data helps solar installers target the right homes.

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G98 vs G99 — the key threshold

Both G98 and G99 are Engineering Recommendations published by Energy Networks Association (ENA). They set out the technical requirements for connecting generation equipment to the UK distribution network. The threshold that determines which applies is 16 amperes per phase of export capacity.

G98 — micro-generation (≤16A per phase)

Export capacity up to 16A per phase
Single-phase: up to ~3.68 kW export
Three-phase: up to ~11.04 kW export
Notification only — no prior DNO approval needed
Submit notification within 28 days of commissioning
No application fee
Most residential solar PV installations fall under G98

G99 — larger generation (>16A per phase)

Export capacity above 16A per phase
Full application required before connection
DNO has 45 calendar days to decide (typical)
Application fee payable (DNO-specific)
May require protection relay and type testing
Common for commercial solar, battery, and wind

The G99 application process

If your installation exceeds the G98 threshold, you must apply to the relevant Distribution Network Operator (DNO) before energising the system. The process typically follows these stages:

Pre-application check: Confirm the connection voltage, export capacity, and any protection requirements with the installer or electrical engineer. Prepare technical specifications for the inverter and generation unit.
Submit the application: Each DNO operates its own online portal (e.g. NGED's Connections Portal, UKPN's Connections Online). Submit the G99 Application Form Part A with technical details and site address. Pay the application fee.
DNO review: The DNO acknowledges the application within 10 business days and carries out a network impact assessment. For straightforward low-voltage connections, approval typically comes within 45 calendar days. Complex cases may require a feasibility study and additional fee.
Offer issued: If the network can accommodate the connection without reinforcement, the DNO issues a connection offer. If reinforcement is needed, costs are shared under the relevant charging methodology.
Commissioning: Once installed, the installer submits the Commissioning Form (G99 Part B) to the DNO confirming the unit is connected in accordance with the approved design. A commissioning test is performed to verify protection settings.

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FAQ

What is the difference between G98 and G99?

G98 applies to micro-generation units with an export capacity of 16A per phase or less. G99 applies to all generation above this threshold. G98 requires only a post-commissioning notification to the DNO; G99 requires a full application and approval before the system can be connected.

How long does a G99 application take?

Under the Engineering Recommendation G99, a DNO must acknowledge a complete application within 10 business days. Straightforward low-voltage connections are typically decided within 45 calendar days. Complex applications involving network reinforcement or high-voltage connections may take longer.

Do I need a G99 application for a 5kW solar system?

It depends on the inverter's configured export capacity, not the panel peak power. A 5kWp system with an inverter configured to export at 16A or below on a single-phase supply can use the G98 notification process. If the inverter exports above 16A, G99 applies. Check the inverter specification and confirm with a qualified electrical engineer.

Which DNO should I apply to?

The correct DNO is determined by the property's location. The six licensed DNOs in Great Britain are: National Grid Electricity Distribution (NGED), UK Power Networks (UKPN), Northern Powergrid, SP Energy Networks, Electricity North West, and SSE Networks. Your installer or the Energy Networks Association website can confirm which DNO covers a specific address.

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