Solar Panel Installer Widnes, an independent guide / The grid

G98 and G99: notify after, or apply first

Two engineering documents decide how a home generator is connected in Great Britain. Which one applies to you depends on a single number on the inverter's label, and on whether a battery brings an inverter of its own.

Sources checked on 3 November 2026. Written by SEO Dons, which sells and fits nothing.

Side by side

The two connection routes for a home system
	G98	G99
Covers	Inverters exporting up to 16 A per phase in total	Everything above that, battery inverters included
Sequence	Install, switch on, notify within 28 days	Apply, wait for a reply, then install and switch on
Conditions	None in advance	Possibly an export limit or design changes
Who acts	The installer	The installer, with your signature on the application

The number that decides it

The threshold is about what the inverters can push onto the cables, not the panels' combined rating. That is why eleven 440 W panels, 4.84 kWp, can sit on the notify-after route behind a 3.68 kW inverter. On a three-phase supply the limit is 16 amps on each phase, 11.04 kW in all, provided the load is spread so no single phase carries more than its share.

Batteries are where homeowners are most often caught out. A battery that shares a hybrid inverter adds nothing to the total, because that one inverter is still the ceiling. A battery with its own inverter adds that inverter's rating: a 3.68 kW solar inverter plus a 3 kW battery inverter makes 6.68 kW, so the system needs approval first, even though the panels have not changed. Adding a battery to an existing system later can change the route in the same way.

The network in Widnes

SP Energy Networks runs the local cables under its SP Manweb licence. Halton Borough Council's infrastructure plan of 2010 recorded the whole borough as on that network, and the council's own grid offer for its microgrid at Ditton came from the same company in 2021. The same plan noted electricity constraints around Widnes Waterfront at that time. Whether any constraint touches your street today is something only an application would show.

When an application is needed

A G99 application describes the inverters, any battery, the protection settings and any export limit. The network may accept it as it stands, ask for a limit on exports, or ask for a change. Timing varies; for a larger home system it can add weeks, which a good quote will allow for. Under G99 an export limit is part of the design that is approved; on its own it does not move a system back to the notify-after route.

Six systems and their routes

Example Widnes systems on a single-phase supply
System	Inverters could export	Route
8 panels, 3.6 kW inverter	3.60 kW	G98: notify after
11 panels, 3.68 kW inverter	3.68 kW	G98: notify after
11 panels, 3.68 kW inverter, battery with its own 3 kW inverter	6.68 kW	G99: apply first
14 panels, 3.68 kW inverter	3.68 kW	G98: notify after
14 panels, 5 kW hybrid with battery	5.00 kW	G99: apply first
14 panels, 5 kW hybrid, 3.68 kW export limit	5.00 kW	G99: apply first

Two of these surprise people. The battery example has the same panels as the eleven-panel system above it but needs approval, because its battery has an inverter of its own. And fourteen panels on a 3.68 kW inverter stay on the simpler route, at the cost of clipping about 4.8% of their output: the trade the connection checker lets you weigh.

Three-phase homes

A few homes have a three-phase supply. There the notify-after limit is 16 amps on each phase, up to 11.04 kW of inverters in all, provided they are spread so that no phase carries more than its 3.68 kW. A single-phase 5 kW inverter connected to one phase of a three-phase supply is over the limit for that phase and still needs approval; a three-phase inverter of the same rating, which shares its output across the phases, does not. The installer can tell which supply you have from the meter and the main fuse.

Changes after switch-on

The route depends on the system as it ends up, not as it started. Adding a battery with its own inverter, swapping the inverter for a larger one, or adding a second array with an inverter of its own all change the total that could be exported, and each needs a fresh notification or, if the new total is over the limit, an application. Removing an export limit is a change too. Keep the original papers, because the next installer will ask for them.

What it means for the quote

An application adds time rather than much cost, but it should be visible on the quote: who prepares it, whether the price depends on the answer, and what happens if the network asks for a limit. Weigh those terms alongside the price on prices, and use the questions on choosing an installer to get them in writing.

Papers to keep

The G98 notification, or the G99 approval with any conditions.
A note of the inverter settings, including any export limit.
The MCS certificate and the electrical installation certificate.
Product datasheets and warranties for the panels, inverter and any battery.

You will want these if you sell the house, add a battery, or apply for an export tariff. See after switch-on for the rest of the paperwork.

Sources for this page

Questions about G98 and G99

Do I have to tell anyone before solar panels are connected in Widnes?

For a small system, no: the installer connects it and notifies SP Energy Networks within 28 days. For a larger one, the installer applies first and waits for an answer. Either way it is the installer's job, not yours.

How long does a G99 application take?

It varies with the size of the system and the state of the local network, and can add several weeks. A quote for a larger system should say whether an application is needed and allow for the wait.

Can SP Energy Networks refuse a home solar system?

It can attach conditions to a larger system, most often a limit on how much may be exported, or ask for changes to the design. Systems on the notify-after route are not refused in advance.

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