G99 is the set of rules for connecting generation, such as solar panels and batteries, to the electricity grid in Great Britain. If your system is bigger than 16A per phase (3.68kW), you need approval from the network operator before you connect it.
G98 or G99?
| G98 | G99 | |
|---|---|---|
| Size | Up to 16A per phase (3.68kW) | Over 16A per phase |
| When you tell the network operator | After install, within 28 days | Before install: apply and wait for approval |
| Typical use | Small home systems | Larger homes, businesses, farms and solar farms |
The limit is based on the inverter’s output, not the panels. Batteries count too if they can export to the grid. Almost every commercial, farm or utility-scale system needs G99.
The four types
G99 sorts generation into four types by size. The bigger the type, the more technical studies and tests are needed.
- Type A: small systems, up to 1MW
- Type B: 1MW to under 10MW
- Type C: 10MW to under 50MW
- Type D: 50MW and over, or anything connecting at 110kV or above
Most commercial rooftops are Type A. Many solar farms are Type B.
How the application works
- Check who runs your local network. In the South West, the Midlands and South Wales, it is National Grid Electricity Distribution (NGED).
- Fill in the G99 form. It asks for the equipment, the site layout and a location plan, plus the inverter and battery data sheets.
- Submit it with your connection application. The network operator checks whether the local network can take it.
- Get a quote. NGED’s published standard for a generation quote is 45 working days at low voltage and 65 working days at high voltage.
- Accept, pay and build. Some upgrades on the network can take much longer than the paperwork.
- Commission and test. Larger systems need extra tests, and the network operator may want to witness them before you export.
What causes delays
- Missing data sheets or the wrong inverter model on the form.
- No export limit plan when the local network is busy. An export limit can turn a “no” into a “yes”.
- Layout drawings that don’t match what gets built.
- Leaving it too late. Apply as soon as the design is fixed, not when the panels arrive.
How we help
We prepare G99 forms and connection applications, submit them and chase them with the network operator, for commercial systems and solar farms. Our software fills G99 forms from your site records, and nothing goes out until you approve it.
Grid application and G99 fee → · Grid consultancy →
Sources
- NGED: generation (G99) applications
- NGED: connection guaranteed standards of performance
- GivEnergy: G98 vs G99, what’s the difference?
Facts last checked 25 October 2026. Rules and timescales change. Check with your network operator before you build.