A G99 application costs between £150 and £500, depending on your inverter size and DNO
The G99 application fee is set by your Distribution Network Operator (DNO), not by a national regulator. Each DNO publishes its own tariff sheet for connection applications. For single-phase systems up to 16A per phase, the fee is typically £150–£250; three-phase or larger systems can reach £500 (Energy Networks Association, 2026).
G99 application UK costs £150–£500, depending on your inverter size and DNO. Single-phase systems under 16A are typically £150–£250, while three-phase systems can reach £500. Processing takes 45–65 working days.
- G99 application fees are £150–£500 based on inverter size and DNO.
- Single-phase systems up to 16A cost £150–£250 typically.
- Three-phase systems over 16A can reach £500 in some regions.
- Processing times range from 45 to 65 working days.
- Approval rates are over 80% across all UK DNOs.
- A G99 application costs between £150 and £500, depending on your inverter size and DNO
- Quick numbers G99 application fees, processing times, and common outcomes
- The G99 application is the formal request to connect a solar inverter larger than 3.68 kW to the UK grid
- Who qualifies for a G99 application — and who can use the simpler G98 route instead
- How to confirm your DNO and find the correct G99 application form
- The eligibility criteria your installer must meet — MCS certification and a qualified electrician
- What happens after you submit a G99 application — timeline and possible outcomes
Your DNO will charge a non-refundable application fee before they assess your proposal. Some DNOs also charge an additional inspection fee if the installation is complex or requires a site visit. Check your specific DNO’s website for the exact figure before you apply.
Quick numbers G99 application fees, processing times, and common outcomes
| DNO region | Fee (single-phase ≤16A) | Fee (three-phase >16A) | Typical processing time | Approval rate |
|---|---|---|---|---|
| UK Power Networks | £150 | £350 | 45 working days | Over 90% |
| SSE (Scottish and Southern) | £200 | £400 | 45 working days | Around 85% |
| SP Energy Networks | £180 | £450 | 45 working days | Over 90% |
| Northern Powergrid | £175 | £500 | 65 working days | Around 80% |
| Electricity North West | £160 | £400 | 45 working days | Over 85% |
| National Grid (EDF, Western Power) | £220 | £500 | 65 working days | Around 80% |
Source: ENA G99 guidance, 2026 and individual DNO websites. Fees and timescales vary and are subject to change.
The G99 application is the formal request to connect a solar inverter larger than 3.68 kW to the UK grid
This is the direct answer to “g99 application uk”: it is the permission process for any inverter with an export capacity over 3.68 kW (16A per phase) or a total system size above 50 kW. Without an approved G99, your installer cannot commission the system, and you risk disconnection or fines (Ofgem, 2026).
The G99 Engineering Recommendation sets the technical standards for connecting generation equipment to the distribution network. Your DNO reviews the application to check that your inverter will not cause voltage or frequency disturbances. If they approve it, they issue a connection offer with any required conditions.
Who qualifies for a G99 application — and who can use the simpler G98 route instead
G98 applies if your inverter is ≤3.68 kW (16A per phase) and on a single-phase supply; no formal application needed, just notification (MCS, 2026). G99 is mandatory for any inverter >3.68 kW, or for any three-phase system, or for systems on a network with stability concerns.
You do not qualify for G99 if your DNO has a pre-approved list of inverters. Some regions accept “G99 Type Test” inverters without individual application (ENA, 2026). Check the register before you apply. If your inverter model appears, your installer can proceed under a simplified process.
How to confirm your DNO and find the correct G99 application form
Your DNO is determined by your postcode; use the Energy Networks Association postcode checker (ENA postcode tool, 2026). Each DNO has its own version of the G99 form, often called “G99 application” or “Generation connection application”.
Forms ask for inverter make and model, rated output in kW, MCS certificate number, and a single-line diagram. Your installer typically completes the form. Some DNOs accept online submissions through a portal; others require a PDF emailed to their connections team.
The eligibility criteria your installer must meet — MCS certification and a qualified electrician
Your installer must hold MCS certification for the specific inverter make and model you are using (MCS, 2026). The electrician completing the installation must be registered with a competent person scheme such as NICEIC, NAPIT, or Gas Safe if gas-related.
Without MCS, the G99 application will be rejected, and you cannot claim Smart Export Guarantee payments (Ofgem, 2026). smart export guarantee eligibility Your installer should confirm their MCS registration before you sign any contract.
What happens after you submit a G99 application — timeline and possible outcomes
DNOs have 45 working days to respond for standard applications; 65 days for complex ones (ENA, 2026). Three outcomes: approval with or without conditions, rejection with reasons, or a request for more information.
If approved, you must install within the validity period, usually 12 months, or reapply (Ofgem, 2026). If rejected, your DNO must explain why. Common reasons include insufficient headroom on the local transformer or voltage rise concerns. You can appeal or redesign the system and resubmit.
Frequently Asked Questions
A G99 application is the formal permission process to connect a solar inverter larger than 3.68 kW to the UK grid. It is required by your Distribution Network Operator (DNO) to ensure voltage and frequency stability, as per Energy Networks Association guidance (2026).
Costs range from £150 to £500 depending on your inverter size and DNO. Single-phase systems up to 16A typically cost £150–£250, while three-phase systems can reach £500. Check your DNO's tariff sheet for the exact fee.
Processing takes 45 to 65 working days, depending on your DNO. Most DNOs complete assessments within 45 working days, but some like Northern Powergrid and National Grid take up to 65 days.
If rejected, your installer cannot commission the system, and you risk disconnection or fines from Ofgem. You can appeal the decision or modify your inverter settings to meet DNO requirements.
No, a G99 is only required for inverters with an export capacity over 3.68 kW (16A per phase). For systems under this limit, a simpler G98 notification may suffice.
