Grid connection

Adding a battery to an existing solar install can trip a G98 system into G99 territory, and that changes the paperwork

Grid Guru's August 2026 newsletter spells out the threshold that catches a lot of retrofits: an AC-coupled battery with its own inverter can push a 3.68 kW single-phase system over the 16 A per phase G98 limit, which means a full G99 application, approved before installation, rather than the simple notify-after-fitting G98 route.

20 August 2026 · Source: Grid Guru

Most standard rooftop installs in Herne Bay went in under G98, the notify-your-DNO-after-the-fact route covering anything at or under 16 A per phase, 3.68 kW on a single-phase supply. Adding a battery later is where it gets more complicated, and the answer depends on how the battery is wired in, not just how big it is.

An AC-coupled battery has its own inverter, separate from the solar inverter, and its export capacity stacks on top of what's already there. Add a 3.6 kW AC-coupled battery inverter to an existing 3.68 kW solar system and the combined figure is over the G98 ceiling, meaning UK Power Networks needs to approve a G99 application before the battery goes live, not after. A DC-coupled battery sitting behind the existing hybrid inverter is a different case, since it often doesn't increase the site's export capacity at all and can keep the original G98 notification valid.

The Herne Bay Conservation Area covers 41 Grade II listed buildings, including Telford Terrace and the Hanover, Brunswick and Oxenden squares, and a good number of those homes went solar under the simpler G98 route. Anyone weighing up adding storage now should ask their installer directly which wiring approach they're proposing and whether it changes the DNO paperwork, before assuming a battery add-on is as quick as the original install was.

Nothing here changes the underlying VAT or SEG position, both of which stay live and worth using regardless of which grid connection route a battery ends up needing.

Read the original: Grid Guru. Commentary is Herne Bay Solar's own editorial view; the original reporting is credited to its publisher.

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