G98 and G99 Explained: Connecting a Home Battery to the UK Grid
- G98 and G99 are Energy Networks Association connection rules for small generation and storage.
- G98: smaller systems up to 16 A per phase are connected and then notified.
- G99: larger systems need the network operator's permission before connection.
- Solar plus battery together can push a home into G99.
- Your installer normally handles the notification, but you should ask to see it.
In the UK, a home battery that can feed the grid has to be reported to your network operator. G98 is the simple notify-afterwards route for smaller systems, while G99 needs approval first.
Why the grid needs to know
A battery that can export electricity counts as generation as far as the network is concerned. The local network operator (the DNO) needs to know what is connected so it can keep the street's wiring safe and stable. The rules that set this out are the Energy Networks Association engineering recommendations known as G98 and G99.
G98: connect and notify
G98 covers fully type-tested systems up to 16 A per phase, which on a normal single-phase home is about 3.68 kW. The installer notifies the DNO within 28 days of installation. No permission is needed first, according to the MCS guidance we read.
Because it is simpler, most small battery-only installs aim for this route where the product allows it.
G99: ask first
Above the 16 A per phase level, you need the operator's approval before connecting. The MCS guidance says an integrated solar and battery system will often exceed that and fall under G99, with an application submitted before installation. A fast-track route exists for some systems above 3.68 kW that use an inverter type-tested to G98 and where the storage does not operate when the grid fails.
The MCS table does not spell out how every standalone battery above 3.68 kW is classed, and DNOs can ask for their own forms. So the safe approach is to confirm with the DNO, or ask your installer to confirm in writing.
Good to know
Do not accept a verbal assurance that the DNO has been told. Ask for the reference or confirmation.
What you should do
Ask the installer which route applies to your system and who submits it. Keep a copy of the notification or approval with your commissioning paperwork. This can matter when you sell the house or claim on a warranty or insurance.
Plug-in solar became legal in Great Britain on 27 August, but plug-in batteries were not part of that change, so they do not give you a way round these rules. Our guide to plug-in batteries explains where that stands. For installed systems, a good installer will make the grid side routine. See also our UK country guide for the wider rules.
Common questions
Do I need DNO permission for a home battery?
It depends on the size of the system. Smaller systems are notified after installation (G98), and larger ones need approval first (G99). Your installer should confirm which applies.
Who submits the G98 or G99 paperwork?
Normally the installer. Check this is in the quote, and ask for a copy of what they submit.
Does adding a battery to existing solar change the connection route?
It can, because the combined system may be larger than your existing notification covered. Tell the installer about your existing setup.
What if my battery is not set to export?
Whether an export limit changes the route depends on the product and the DNO. We could not confirm a general rule, so ask the DNO or installer.
Related guides
Want to know which battery size fits your home?
Use our free calculator to get a size, savings and payback estimate.