Who runs the network in the borough
Electricity North West runs the cables and substations that carry power to and from homes across the Wigan borough; on its own pages it also appears as SP Electricity North West. It is not your energy supplier, and you will rarely deal with it directly, but anything in a home that generates or stores electricity connects to its network, and its micro-generation page puts the rule in one sentence: anyone planning to connect generators or storage must inform it or complete an application (Electricity North West).
Those connections add up. Government figures count 6,529 solar PV installations of every size in the borough at the end of 2025, against 4,399 at the end of 2020, a rise of 48% by our arithmetic (DESNZ). Every new system now goes through one of two routes, G98 or G99. For a household, the practical points are that the installer handles the paperwork, and that the quote should say which route applies before you sign. The glossary has short definitions of both.
G98: fit first, then tell the network
Most home systems fall under G98. Electricity North West says it applies to all generation installations up to 16 amps per phase, which means up to 3.68 kW on a single-phase supply and up to 11.04 kW on a three-phase one, and that the rating of an installation is taken to be the inverter's continuous steady state rating (Electricity North West). The figure that counts is the inverter's, not the total of the panels, which is why a quote should name the inverter and give its rating.
Under G98 the installer commissions the system first and notifies afterwards. MCS tells installers that for solar PV under G98 the network operator needs to be notified within 28 days of the system being commissioned (MCS), and for a single home Electricity North West asks for its G98 Form B, returned by email (Electricity North West). Ask the installer for a copy of the form it sends. It belongs with the MCS certificate in the papers you keep, and anyone who later adds a battery or a heat pump will want to see it.
One home or several makes a difference too. Electricity North West says that for a generator or storage at a single premises it is unlikely to need to do any work on the network, but that at multiple premises it may need to, and the notice is then made on its G98 Form A instead (Electricity North West). In a borough where 71.7% of households live in a semi or a terrace (Census 2021, our arithmetic), neighbours may sign up with one installer together, or a landlord may fit a whole row at once. Ask whether the installer is treating the job as separate homes or as one scheme across several, because the network answer can differ.
G99: apply, wait, then switch on
Anything over 16 amps per phase falls under G99, and the order of events reverses. Electricity North West asks for the relevant Energy Networks Association application form, together with a single line diagram of the proposed installation; only once the application has been accepted and the system installed does the commissioning paperwork follow. Its instruction is plain: do not switch on the generation system until the commissioning documents have been reviewed and approved (Electricity North West). MCS puts it the same way to installers: under G99, prior permission to connect is needed (MCS).
For a household that changes the timetable. A G99 application has to be made, and answered, before the system can run, so a quote for a larger system should say when the installer will apply and what happens to the job if the answer takes a while. Electricity North West's G99 page gives no timescales, and this guide does not guess at them; ask the installer what it expects and get the answer in writing. If the network needs anything further, its page says, the engineer will say so and it will be set out in the project specification section of the quote letter it sends.
Two more details from that page are worth knowing. If the inverter is not fully type tested, an extra commissioning form has to go in alongside the single line diagram; and for some systems the network attends to watch the commissioning engineer test the protection systems, which it calls witness testing (Electricity North West). A quote for a larger system should say whether either applies, and who pays for the time involved.
Adding a battery
A battery changes the sums, because storage connects to the same network as the panels. MCS's guidance to installers is that a battery within the G98 limit can be notified on G98 Form B within 28 days of installation, but that where solar with storage goes above 3.68 kW, the application form must reach the network operator before installation. There is also a fast-track form for integrated solar and battery systems, which likewise has to be submitted before installation (MCS).
So a battery added a few years after the panels can move a home from one route to the other. Tell whoever fits it what is already on the roof, ask which route the combined system falls under, and see batteries for sizing and prices. MCS says heat pumps are notified to the network operator as well, with their own rules on when; solar with a heat pump covers how the two fit together.
The inverter matters again at the end of its working life. A replacement with a higher rating than the original, or one that also runs a battery, can change the route, so treat a replacement as a fresh question for the network rather than a like-for-like swap, and ask the firm doing it whether a new notice or application is needed.
Export limiting
Export limiting is a setting or a device that caps how much power a system can send out to the network, so that the panels and battery can be larger than the export the network has agreed to. Electricity North West's G99 page lists a G100 Form C among the documents to submit where export limitation applies (Electricity North West). Whether it suits a particular home depends on the network at that address and on how much of the power the household will use itself, which only the installer's design and the network's answer can settle.
If an installer proposes it, ask three things: what export limit it will set, how that setting is protected from being changed, and what the limit does to the yearly estimate of power sent out, which matters for an export tariff. A system that is limited should say so in the papers you keep.
What the quote should say about the network
A good quote leaves no doubt about the network. The table sets out the differences; the list after it is what to look for on paper.
| G98 | G99 | |
|---|---|---|
| Size | Up to 16 A per phase: 3.68 kW single-phase, 11.04 kW three-phase | Over 16 A per phase |
| What is measured | The inverter's continuous rating | The same; solar with storage over the G98 limit lands here |
| When the network hears | Within 28 days of commissioning | Before installation, by application |
| Paperwork | G98 Form B for a single home | An ENA application form and a single line diagram, then commissioning documents |
| Switching on | After commissioning | Only once the commissioning documents are reviewed and approved |
- The route, G98 or G99, and the reason for it.
- The inverter's make, model and rating, and whether it is fully type tested.
- Who sends the notice or application, and when; for G99, whether it goes in before you are asked to pay more than a deposit.
- Any export limit, and the figure it is set at.
- Copies of everything sent to Electricity North West, for your records.
MCS also advises checking that every price covers commissioning the system (MCS), the step that comes before the G98 notice. What a quote should include sets out the rest of the paperwork, the costs page gives the North West prices to compare against, and checking a solar installer covers the firm itself.
If no copy of the notice reaches you within a few weeks of the system being switched on, ask for it. MCS guidance is that a G98 notice goes in within 28 days of commissioning, so a firm that cannot produce one after that has a gap in its paperwork, and it is worth closing before a battery or a heat pump is added. Raise it in writing, as you would any other missing document.