G98 and G99 are the two routes for connecting solar panels or a battery to the electricity network in Great Britain. The difference comes down to size and timing. G98 covers smaller systems, up to 16 amps per phase, and works on a fit-first, tell-later basis: your installer connects the system, then notifies your network operator within 28 days. G99 covers everything larger, and works the other way round: the network operator must approve the connection before installation starts.
If you are having an ordinary home solar system fitted, you will probably never need to think about either, because your installer handles it. But if you want to know what is actually happening with your paperwork, or you are planning something bigger, here is the whole picture.
What the threshold actually means
The dividing line is 16 amps per phase of generating capacity. On a standard single-phase household supply that works out at about 3.68 kW of inverter capacity. On a three-phase supply, around 11.04 kW.
Note that the limit applies to the inverter, not the panels, and it aggregates everything that generates. A battery inverter counts. So a house with a 3.6 kW solar inverter that adds a separate 3.6 kW battery inverter has just crossed the line, and the addition needs a G99 application even though each piece alone would have been fine. This catches people out constantly, and it is one of the first things we check when quoting a battery retrofit.
How G98 works
Your installer commissions the system, then submits a notification form to your distribution network operator, the company that runs the local wires, within 28 calendar days. The form covers the site, your MPAN (the number on your electricity bill), the equipment, its type-test reference and the installer's declaration. For a single home this is Form B. There is no waiting and no approval step. It is a notification, not a request.
How G99 works
Anything above the threshold needs the network operator's approval before work starts, because a larger system can affect the local network. The application covers your site, the equipment's technical details, and what you want to import and export. The operator assesses whether the local network can take it. Sometimes the answer is yes as asked. Sometimes it comes back with a condition, most commonly an export limit, which is handled through a scheme designed to a third standard called G100 that caps what your system can push onto the grid while letting you generate freely for your own use.
How long does it take? Honestly: it depends, and be wary of anyone quoting a fixed period. What is regulated is the time to issue a connection quotation, with published standards of 30 working days for smaller low-voltage cases and longer for complex ones. The overall journey depends on the local network, whether reinforcement is needed, and how complete the application was in the first place. A well-prepared application for a modest system is often straightforward. A large system on a constrained bit of network is not.
The Fast Track shortcut. For qualifying smaller installations, including many home solar-plus-battery combinations just over the G98 line, network operators run a streamlined G99 route. The criteria are technical, covering per-unit and aggregate capacity limits and type-tested equipment, but where a project qualifies it takes much of the waiting out. We check eligibility as standard.
What does it cost? For our region, domestic connection quotations covering up to four properties are currently not chargeable. Larger and more complex cases can attract assessment and design fees. There is no single universal "G99 fee", so treat any flat figure you read elsewhere with caution.
Who is my network operator?
Not your energy supplier. Your distribution network operator depends on where you live: across most of the North West it is Electricity North West across Greater Manchester, Lancashire and Cumbria, and SP Energy Networks across Merseyside, most of Cheshire and North Wales. Your installer deals with them on your behalf, which is the way it should be.
What this means in practice
Standard home solar: G98, handled after installation, nothing for you to do.
Home solar plus battery, or a battery retrofit: depends on the combined inverter capacity. Often G99, frequently Fast Track eligible. Worth checking before you sign with anyone.
Commercial systems: almost always G99, applied for properly before anything is ordered. On constrained networks, expect an export-limitation conversation.
Inherited a system with no paperwork? It happens a lot, especially where the installer has gone bust. Retrospective notification is possible and worth doing: the record matters for export payments, insurance and selling the property. We can sort it.
We prepare and submit all of this as part of every installation, because a bounced application costs weeks. If you just want the forms handled by someone who fills them in every week, that is part of the job. DB Energy is MCS certified for solar PV and battery storage, certificate NIC-601172.
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