G98 vs G99: grid connection applications for installers

Every solar PV array, battery or vehicle-to-grid charger that can run in parallel with the network needs the distribution network operator (DNO) to know about it, and sometimes to approve it first. Which route applies comes down to two Energy Networks Association (ENA) Engineering Recommendations: G98 and G99. Get the choice wrong and a finished installation can sit switched off while the DNO catches up, or be connected without the approval it needed.

This guide explains the G98 vs G99 decision, the G99 application process including the fast track route, where export limitation fits, and what changed for storage in 2026. It is based on EREC G98 Issue 2 and EREC G99 Issue 2, both published on 10 March 2025 with new storage requirements in force from 1 March 2026, and on the ENA's Distributed Generation Connection Guide (March 2026).

The short answer

G98 covers Fully Type Tested micro-generation up to and including 16 A per phase in total at a single premises: 3.68 kW on a single-phase supply or 11.04 kW on three-phase. It is "fit and inform": install, commission, then notify the DNO within 28 days. Anything bigger falls under G99, which means applying to the DNO and waiting for approval before connecting. Small type-tested solar and battery systems above 16 A per phase can often use the G99 fast track, which cuts the DNO response to 10 days or less.

What are G98 and G99?

G98 and G99 are ENA Engineering Recommendations (ERECs) that sit under the Distribution Code. They set the technical and process requirements for connecting generation in parallel with the public distribution network in Great Britain.

• EREC G98: requirements for the connection of Fully Type Tested micro-generators, up to and including 16 A per phase, in parallel with public low voltage distribution networks.

• EREC G99: requirements for the connection of all other generation equipment in parallel with public distribution networks, from domestic systems just over 16 A per phase up to large power stations.

Both replaced the older G83 and G59 recommendations for generation connected from 27 April 2019. They apply to any source that can run in parallel with the network, which includes solar PV, wind, small hydro, CHP, battery storage and vehicle-to-grid (V2G) chargers. In GB law, electricity storage is a form of generation, so a battery is assessed in exactly the same way.

Northern Ireland uses its own versions, G98/NI and G99/NI, with G99/NI Issue 2 published on 1 May 2026. The detail in this guide is for GB.

The 16 A per phase threshold

The G98 vs G99 decision turns on one figure: 16 A per phase, which equates to 3.68 kW single-phase or 11.04 kW three-phase. Three points decide whether a job is under or over it.

• It is the total at the premises, not per device. The threshold applies to the aggregate capacity of all micro-generators at a single premises, including anything already installed. A 3.6 kW PV system already notified under G98 plus a new battery will usually push the site into G99.

• It is Registered Capacity, not panel wattage. For inverter-connected equipment, Registered Capacity is the lesser of the inverter rating and the rating of the energy source. A 5 kWp array on a 3.68 kW inverter is a 3.68 kW generator.

• Storage counts. A battery inverter that can export adds to the total. Where several inverter-connected units are installed together, the route is based on their total installed capacity; for synchronous machines it is based on each unit.

The DG Connection Guide also distinguishes Intrinsic Design Capacity (what the equipment is built to produce) from Registered Capacity (what it is set to deliver). That difference matters for the fast track route below.

G98 vs G99 at a glance

G98: fit and inform

For a single premises, the ENA describes G98 as "fit and inform". The steps are:

• Use a competent installer and Fully Type Tested equipment. All G98 micro-generators must be Fully Type Tested, meaning the whole unit has been tested, not just part of it. Type test evidence is now held on the ENA's Connect Direct portal, which replaced the old ENA Type Test Register in April 2024.

• Install and commission in line with G98, BS 7671 and the manufacturer's instructions, including safety labelling and loss-of-mains disconnection.

• Notify the DNO within 28 days of commissioning using the Installation Document (Form B in G98), or the DNO's equivalent online form. The ENA guide describes this notification as a legal requirement.

After connection, the owner must keep the equipment maintained, tell the DNO of any failure that affects G98 compliance, and inform the DNO if the equipment is removed or replaced.

Multiple premises

G98 changes where micro-generators are being installed at several premises in a close geographic region, such as a street-wide retrofit or a new housing development. There you must apply to the DNO first, using Form A in G98, and wait for approval before connecting. The ENA's rule of thumb is that sites within about 500 m of each other, or sharing a postcode up to the last two letters, are likely to be in a close geographic region.

When G98 does not apply

G98 does not apply where one micro-generating plant supplies two or more independent customers through a generation sharing device, for example solar on a block of flats shared between apartments. Those installations go through G99 on Form A1-3.

The G99 application

Above 16 A per phase, G99 applies and the order reverses: apply first, connect later. G99 classifies power generating modules into four types:

Almost all domestic and small commercial work sits in Type A. A standard Type A application runs as follows:

• Submit the Standard Application Form to the DNO, with details of the site, the generation and storage, and the proposed import and export capacity.

• Receive and accept a connection offer. The DNO assesses the impact on its network and sets out the conditions of connection, any export limit and any charges.

• Install and commission in line with the offer and G99, including interface protection settings.

• Submit the commissioning and compliance forms set out in G99. Type tested equipment can usually be commissioned by the installer; non-type-tested or larger plant may need DNO witness testing.

Do not energise before approval. Connecting G99 generation without the DNO's agreement can lead to disconnection and may affect eligibility for export payments. Types B to D involve network studies, witness testing, operational agreements and, for the largest schemes, a generation licence and interaction with the National Energy System Operator.

G99 fast track for solar and storage

Many domestic jobs cross 16 A per phase only because a battery is added to solar. For these, G99 includes a fast track for Fully Type Tested integrated micro-generation and storage, known as the Small Generation Installation (SGI) procedure. Applications are made on G99 Form A1-2, and the ENA guide says the fast track cuts the DNO's confirmation from 45 days to 10 days or less.

Since a Distribution Code modification approved by Ofgem, there have been three SGI categories:

All figures are per phase. SGI-1 covers a unit built to a larger capacity but limited, for example by manufacturer software, to a Registered Capacity of 16 A. All new and existing units, including storage, must be at a single installation and connected through G98 or G99 Fully Type Tested inverters, and any export limitation must be an EREC G100 compliant scheme. See, for example, the fast track guidance from SP Electricity North Westand SSEN. SSEN notes that you cannot connect until its assessment is complete, the installer then has up to three months to install and commission, and the commissioning form (Form A3-2) is due within 28 days.

Export limitation (G100)

An export limitation scheme controls how much a site can export to the network, using a sensor at the origin and control of the inverters. It is how a larger system can connect where network capacity is limited, or stay within a fast track category.

• Export limitation schemes must comply with EREC G100.

• G100 is not a separate application. It forms part of the G98 or G99 application and the DNO's assessment.

• Adding export limitation does not automatically qualify a system for the fast track: the equipment, capacities and existing generation all still count.

Some inverters have a manufacturer-set export limit that fixes their Registered Capacity. Where the limit is set by the installer, the scheme must meet G100.

Electricity storage: what changed

Storage requirements in G98 and G99 were aligned with other generation from September 2022: all storage commissioned since then must be fully compliant with G98 or G99. A further change came into force on 1 March 2026 for generation incorporating storage first connected on or after that date, as set out in the foreword to G99 Issue 2: storage devices, when importing, must switch to export if system frequency falls below a defined threshold (G98 clauses 9.4.3 and 9.4.4; G99 clauses 11.2.3.3, 12.2.3.3 and 13.2.5.2).

In practice this means checking that any battery or hybrid inverter fitted now is Fully Type Tested against the current issue. The ENA explains that where a revision changes the technical requirements, manufacturers must re-certify, and previous type test evidence does not cover newly manufactured units. Units already connected under earlier amendments remain valid. For where a home battery can be sited, and how it is ventilated and isolated, see Battery storage under Amendment 4.

EV chargers and V2G

A standard EV charger is demand, not generation. A vehicle-to-grid (V2G) charger that can export from the vehicle battery is generation and follows G98 or G99 like any other storage. The ENA guide includes specific guidance on V2G and EV supply equipment.

Worked examples

Common mistakes

Where BS 7671 fits

G98 and G99 govern the connection to the network; they do not replace BS 7671. The installation itself must meet BS 7671:2018+A4:2026, including Section 712 for solar PV, Chapter 57 for stationary secondary batteries and Chapter 82 for prosumer installations, and must be inspected, tested and certified before the DNO is notified. Surge protection on both the AC side and, where required, the DC side of PV is part of that design: see What Is an SPD in Electrical Installations?. On existing properties, the condition of the installation should be understood before adding generation; an EICR is the usual starting point.

To claim Smart Export Guarantee payments, the installer and products normally need to be certified under the Microgeneration Certification Scheme. MCS certification is separate from the DNO process and does not replace the G98 notification or G99 application.

All current forms, including G98 Forms A and B and G99 Forms A1-1, A1-2 and A3-2, are free to download from the ENA document catalogue, and many DNOs also accept applications online.

Frequently asked questions

What is the difference between G98 and G99?

G98 covers Fully Type Tested generation up to 16 A per phase in total at a premises, which is 3.68 kW single-phase or 11.04 kW three-phase, and only needs notifying within 28 days of commissioning. G99 covers everything above that and needs DNO approval before connection.

Do I need a G99 application for solar and a battery?

Usually, if the combined capacity of the solar and battery inverters is above 16 A per phase. Many domestic systems can use the G99 fast track on Form A1-2, which cuts the DNO response to 10 days or less, provided the equipment is Fully Type Tested and meets the size and export limits.

How long does a G99 application take?

A fast track application is typically confirmed in 10 days or less. A standard G99 application takes longer, because the DNO has to assess the network impact and issue a connection offer; timescales vary by DNO and by the size of the scheme.

Can I connect before the DNO approves a G99 application?

No. Under G99 the DNO must approve the connection before the generation is energised. Only G98 single-premises installations can be connected first and notified afterwards.