G98 and G99 for a home battery: telling the network
Every home battery joins the same local network as the street, so the company that runs it has to know. There is a legal duty behind that, and two engineering routes for meeting it.
In short
The law says the network operator must be told before or at commissioning that a battery will run alongside the network. In practice, systems up to 16 A per phase (about 3.68 kW on a single-phase home) are notified under G98 within 28 days of installation; storage over 3.68 kW, and most panels-plus-battery systems, go through a G99 application before installation.
The legal duty
Regulation 22 of the Electricity Safety, Quality and Continuity Regulations 2002 covers sources of electricity that run in parallel with the network. As well as the requirement to disconnect when the network fails, it says the distributor, your local network operator, must be told of the intention to run such a source before or at the time it is commissioned. Smaller sources, at 16 A per phase or less at low voltage, are exempt from some of the other conditions, but not from telling the operator.
Those other conditions are worth spelling out. Anyone who installs or runs a source in parallel must have equipment that prevents danger or interference with the network and, for a home's low-voltage installation, must meet the British Standard requirements. Above 16 A per phase they must also have the people and procedures to prevent danger, and must agree specific requirements with the network operator. At or below that level those two fall away, as long as the source switches itself off when the network supply goes and the operator has been told by commissioning. So the bigger the system, the more the law expects to be settled with the operator first.
The engineering routes: G98 and G99
The industry's engineering recommendations turn that duty into forms and timings. MCS, in its guidance for installers, is clear that every electricity-generating installation is notified to the network operator, battery storage included.
| G98 | G99 | |
|---|---|---|
| Covers | Up to and including 16 A per phase | Storage above 3.68 kW, and systems over the G98 limit |
| Timing | Within 28 days of installation | Before installation |
| Form for storage | G98 Form B | G99 Form A1.1, or an integrated fast-track form |
| Can bring conditions? | Not usually | Yes, the operator's reply can set conditions |
Demand when charging, generation when exporting
MCS notes that network operators class a battery as demand while it imports from the network. When it sends power the other way, it acts as generation. That is why storage goes through the same notification process as solar panels, even when there are no panels at all.
Why panels and a battery together usually mean G99
The G98 limit is about the total that can flow onto the network from a home. Panels and a battery on the same connection add together, and MCS observes that the combination will often exceed 16 A per phase. So adding storage to existing panels, or fitting both together, commonly takes the G99 route, even when neither part would on its own.
There is a quicker G99 path for that case. MCS describes a fast-track application for solar and storage together where the combined capacity is over 3.68 kW, the inverter is type-tested to G98 standards and the storage will not run when the grid fails. The form still goes in before installation, but the time to connection is shorter. A system designed to keep circuits running in a cut may not meet that last condition, so planning for backup in a power cut can change which application is made.
The number that decides the route is power in kW, set by the inverters, not the battery's capacity in kWh. A battery with a large capacity and a small inverter can be on the simpler route; a small battery with a powerful inverter may not be. kW and kWh explains the difference.
Who does it, and what you should see
Your installer normally prepares and submits the notification or application. National Grid Electricity Distribution, one of the regional operators, puts the G98 route in its own words: for small-scale generation or storage under G98, notify within 28 days of commissioning. Other operators publish similar guidance.
Ask for copies. For G98, a copy of the notification; for G99, the application and the operator's reply, including any conditions. They belong with the electrical certificate and the PAS 63100 statement in your home's records, and you may need them if you later add panels, change the battery or sell the house.
Each route has a follow-up step. Under G98, MCS says the operator reviews the notification and comes back to the installer if anything on it is wrong. Under G99, a separate installation document, the combined A3-1 and A3-2 forms, confirms what was actually fitted to G99 standards after the written application; MCS says it is completed for every Type A power generating facility, and an energy storage system is one. Ask for that document as well.
What G99 means for the timetable
Because a G99 application goes in before installation and the work waits for the reply, it sets the earliest date the job can be done. If you are offered an installation date, ask whether it allows for the reply, and what happens if the reply is late or comes back with conditions.
A note on plug-in solar
The 2026 rules on plug-in solar concern small panels that plug into a socket. The government's response describes them as small solar systems without batteries, with guidance covering G98 notification. They are a different product from home battery storage, which is wired into the home's electrics and notified as above. Regulation 22 itself was amended on 27 August 2026 so that a plug-in microgenerator meets an interim product specification of its own, rather than the British Standard requirements that apply to a wired installation.
For where the battery can physically go, see PAS 63100 in plain words; for the energy side of adding storage to panels you have, storage for existing panels.
Adding or changing equipment later
The notification describes the system as it was installed. If you later add a second battery, more panels or a different inverter, the total that could flow onto the network may change, and with it the route. A system that sat inside the G98 limit can move over it when panels are added, which then needs a G99 application before the extra equipment goes in. Ask any installer quoting for an addition to check what was notified before, and to say which route the enlarged system needs.
If you are not sure a battery was notified
If you bought a home with a battery already fitted, or the paperwork has gone missing, ask the installer named on the electrical certificate for a copy of the notification or application. If that isn't possible, the local network operator can usually tell you whether the system is on its records. Having that confirmed matters before you add anything, and it is the kind of document a buyer's solicitor may ask about.
To work out which operator that is, MCS gives two routes: the postcode search run by the Energy Networks Association, or the first two digits of the MPAN, the supply number on your electricity bill, which identify the distributor. Seven operators run the networks across fourteen districts. Some newer housing developments are on a section owned by an independent operator instead, which is not tied to one region. An operator may also prefer its own version of the forms, which is another reason to let the installer confirm the right one before anything is submitted.
What this page is based on
- Electricity Safety, Quality and Continuity Regulations 2002, regulation 22 (sources running in parallel with the network) (read 3 Nov 2026)
- MCS guidance for installers on telling the network operator (G98 and G99) (read 3 Nov 2026)
- National Grid Electricity Distribution: connecting generation and storage (read 3 Nov 2026)
- Government guidance on plug-in solar devices (2026), PDF (read 3 Nov 2026)
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