Planning solar panels, battery storage or an EV charger and keep hearing about G98 and G99? These are just the rulebooks your installer follows when connecting generation to the grid, but they affect what paperwork is needed and when your project can go ahead.
Do you already have solar or generation?
The first question is whether your property already has any generation connected to the grid, such as solar PV, a small wind turbine or a home battery with an inverter. If you are starting from scratch with a single, modest system, the route is often simpler.
If your home has existing solar, or you are planning more than one device that can export (for example solar plus battery plus an EV charger that can export), your installer will usually need to take a closer look and may lean towards a G99 process.
No existing solar or battery and a fairly standard system size: often G98 notification after installation
Existing solar or plans for multiple export-capable devices: more likely G99 application before installation
Very large systems or unusual setups: almost always G99
From a homeowner’s point of view, the key difference is timing. G98 is usually a simple notification sent to the Distribution Network Operator (DNO) after the installer has commissioned the system. G99 typically means an application has to be approved before the main installation can proceed.
Are you adding battery storage to your system?
Battery storage can either make things straightforward or more complex, depending on how it is connected and controlled. Many modern solar and battery packages are designed to sit comfortably within G98 limits when installed as a single, combined system.
If the installer can configure the system so that the total export to the grid never exceeds a standard small-scale limit, the DNO may allow a G98-style notification or a simplified application route, even if there is both solar and battery on site.
However, where batteries are added separately, or the combined export from multiple inverters could exceed that limit, G99 is more likely. This is because the DNO needs to be confident that, at peak output, your home will not push too much power back into local cables.
Is your inverter rating above typical small-scale limits?
A key factor in G98 vs G99 is the size of the inverter or inverters, measured in kilowatts (kW). G98 is aimed at smaller, standard domestic systems. Once you go above the usual small-scale threshold, G99 tends to apply.
Your installer will look at the total generation capacity on site, not just the panels alone. If you have more than one inverter, they will add these together. Even if you do not intend to export all of that at once, the DNO cares about the theoretical maximum.
To stay within G98, some systems use export limitation devices to cap how much power can flow back to the grid. If the DNO agrees, this can keep the process simpler, but it still needs to be clearly documented on the paperwork.
Do you intend to export, or keep everything for self-use?
Some homeowners like the idea of “off-grid” style setups or keeping everything for self-consumption. In practice, most grid-tied systems still have the ability to export when the battery is full and the house is not using much power.
If your system has any ability to export to the grid, G98 or G99 will apply. Truly zero-export systems usually require extra control equipment and firm limits agreed with the DNO, which again brings you into G99 territory in many cases.
From your perspective, the outcome is about what you can do with your energy. If export is allowed, you may be able to access smart export tariffs. If export is limited or blocked, the design will focus more on covering your own usage and charging your battery instead.
Retrofit scenarios: changing what is already there
Adding a battery to existing solar panels
If you already have solar and want to retrofit a battery, your installer has to look at the full picture. Even if the original solar system was installed under G98, the combined export potential of solar plus battery could push you towards a G99 application.
Sometimes the installer can use an export limitation scheme to keep the total export within G98-style limits, but this still needs to be agreed and documented. The DNO wants a clear record of what is on your property and how it behaves.
Swapping or upgrading an inverter
Replacing a failed inverter like-for-like is often straightforward, but upsizing it or changing the type can change the G98 or G99 position. A larger inverter, or one that can deliver more power to the grid, may trigger G99 requirements.
Your electrician will usually ask for details of the existing system, including the original DNO paperwork if available, so they can see which route was used and whether a fresh application or notification is needed.
Adding an EV charger alongside solar and battery
EV chargers add extra load to your supply, and some smart chargers can also export or interact with the grid. Even if your charger does not export, the DNO is interested in the overall demand and generation on your service.
This is where load calculations matter. Your installer will look at:
The maximum draw of the EV charger, usually 7 kW or more
The generation potential of solar and battery inverters
The size and rating of your incoming supply and consumer unit
If the combination is high compared to your supply capacity, a G99 application and possibly supply upgrades or export limitation may be needed. This is all about keeping the local network safe and reliable.
What your installer needs from you
To work out whether G98 or G99 is likely and prepare the right paperwork, your installer will ask for some basic site information. Having this ready speeds up the design and any DNO submissions.
Before speaking to your electrician, try to gather:
Your MPAN (found on your electricity bill)
Clear photos of your electricity meter and any existing generation meter
Photos of your consumer unit (fuse board) with the cover closed and open
Roof orientation and approximate panel area or existing array size
Existing inverter make, model and rating (from the label on the unit)
With this information, a competent installer can quickly judge whether G98 notification is likely to be sufficient or if a G99 application is required, and explain the steps in plain language.
Next steps and getting helpful guidance
You do not need to become an expert in G98 or G99, but it is helpful to understand that they shape the route your project takes with the DNO. The most important thing is choosing an installer who will handle the design, calculations and paperwork properly.
If you are considering solar PV, battery storage or an upgrade to an existing system, J. Durka Electrical Services can help with both the technical design and the full DNO process so you do not have to wrestle with forms yourself.
For more detail on how systems are designed, have a look at the Solar PV Battery Storage service page and get in touch to talk through your own property and goals.
To discuss your project and get clear advice on whether G98 or G99 is likely to apply, contact J. Durka Electrical Services on 07977479071. The team can review your photos and details, suggest suitable options, and manage the paperwork from start to finish.
