GUIDE · FOR UK SOLAR INSTALLERS · 10 MIN READ

G98 Explained: Notification, Limits and Forms

Every rule and figure below comes from the ENA, Ofgem and DNO sources listed at the end.

What G98 is

Engineering Recommendation G98 is the Energy Networks Association document titled "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".

G98 and G99 were created in 2018 to bring the GB Distribution Code into line with the EU Requirements for Generators network code, as the successors to G83 and G59 (Ofgem's July 2018 decision), and apply to connections from 27 April 2019. Northern Ireland uses different versions; this guide covers Great Britain.

The 16A-per-phase limit and what counts

The ENA guide puts 16A per phase at 3.68kW on a single-phase low-voltage supply and 11.04kW on a three-phase supply, and is clear that it "refers to the aggregate Micro-generator capacity installed in a single premises". That catches more than people expect:

Fully Type Tested kit and Connect Direct

Every Micro-generator connecting under G98 must be Fully Type Tested: the whole unit, not just part of it. The manufacturer proves this with a Type Test Verification Report (G98 Form C).

The ENA's old Type Test Register closed on 16 April 2024 and moved to the Connect Direct portal, where manufacturers maintain their reports and each product carries a compliance status and a System Reference number. A "compliant" status is indicative (DNOs can still review suitability), and non-compliant generation must not be connected. Connect Direct is also an application portal, which the ENA describes as aimed at smaller domestic devices. Either way, check the inverter and battery there when you spec the job and keep the device reference numbers for the notification.

Single premises vs multiple premises

Single premises. The ENA guide summarises it as "fit and inform". Under the Electricity Safety, Quality and Continuity Regulations you don't need to contact the DNO in advance if everything at the premises totals 16A or less per phase at low voltage. You notify within 28 days of commissioning.

Multiple premises. If you are installing G98 Micro-generators at several premises in a "close geographic region", you need the DNO's approval before connecting. Submit Form A before anything is installed, accept the DNO's connection offer (which can include a connection charge), then send a Form B for each installation within 28 days.

What counts as close varies. The ENA guide's rule of thumb is within 500 metres of each other, or postcodes matching up to the last two letters. NGED defines its local region as 500m from each installation, where other G98 installs there are connected or proposed within 28 days of the application. SSEN asks for approval where the same installer has fitted generation at another property in the same postcode (ignoring the last two characters) within 28 days.

The G98 forms (and the G99 ones next door)

Form letters come from G98's Appendix 3, per the ENA guide; the G99 names are as SSEN and NGED list them. DNOs may publish their own versions or an online equivalent.

How to notify, step by step

The single-premises route, from the ENA guide and NGED's process:

1. 1

   Add up everything at the premises

   New inverters, batteries and any generation already there. If the total is over 16A on any phase (3.68kW single-phase, 11.04kW three-phase), stop: it's a G99 job.

2. 2

   Check the kit is Fully Type Tested

   Look the inverter and battery up on Connect Direct before you quote.

3. 3

   Check for other installs nearby

   If you've fitted, or plan to fit, other G98 systems in the same close geographic region, it's a multiple-premises job and needs DNO approval first (see below).

4. 4

   Install and commission

   To BS 7671 and the manufacturer's instructions, unmodified, labelled, and disconnecting if the mains supply is lost. NGED also wants a circuit diagram displayed on site.

5. 5

   Notify the DNO within 28 days

   Submit Form B, or your DNO's online form, within 28 days of commissioning. The ENA guide calls this a legal requirement, and it falls on the installer.

Not sure which network operator to send it to? The first two digits of the MPAN tell you; our guide to DNO applications for solar and finding the right DNO walks through it.

What changes when you go over G98

Above 16A per phase the job is a G99 Type A connection (over 16A per phase to under 1MW). The big change is timing: you apply and wait for approval before connecting, rather than notifying after.

For small systems, DNOs run a G99 fast track. NGED and SSEN publish the same three Small Generation Installation (SGI) categories:

NGED says it responds to fast-track applications within 10 working days and SSEN aims to; the ENA guide contrasts that with 45 days. Outside the fast track, the ENA guide points systems under 50kW three-phase (17kW single-phase) to the simplified G99 form A1-1 and larger ones to the ENA standard application form. The full process is in our G99 application guide for commercial solar.

Export limitation is how SGI-2 and SGI-3 work, and it must comply with EREC G100. Since revisions to G99, the G100 devices used for the small-installation procedures must themselves be Fully Type Tested.

Batteries and hybrid inverters

• Storage is generation in GB law. The ENA guide says PV plus storage is likely to be above 16A per phase, so G99 applies.
• Storage designed to run in island mode (during a power cut, say) can't use the fast track.
• Storage installed after January 2026 must, when importing, switch to export if grid frequency falls below a set threshold. Check the product's compliance is current.
• A hybrid inverter with a design capacity above 16A, limited to 16A or below with the manufacturer's facility, fits NGED's SGI-1 notify-only route (if the site total stays within 16A), not G98.

G98 vs G99 at a glance

Common G98 mistakes

• Forgetting the battery. Storage counts. The ENA guide says PV plus storage is likely to take you into G99.
• Treating a cluster of jobs as separate fit-and-inform installs. Several installs close together need Form A and approval first. Check your DNO's definition of a close geographic region.
• Missing the 28 days. The window runs from commissioning, including the commissioning day itself, per the ENA guide.
• Quoting kit that isn't on Connect Direct. G98 needs Fully Type Tested equipment. Check before the proposal, not after the install.

Where DNOs differ

The rules are the ENA's; the paperwork is each DNO's. Two examples:

• NGED recommends its online form: around 10–15 minutes, with instant acknowledgement. You need device reference numbers, the site postcode and installer and customer details; Form B (single) or Form A (multiple) can go by email or post instead.
• SSEN asks for G98 Form B by email, with the address and MPAN, the total capacity and the inverter's type test certificate.

Check the current page for the DNO that serves the site.

Commercial jobs are usually G99

At 11.04kW on a three-phase supply, G98 rarely covers a commercial roof. Plan commercial jobs as G99 from the commercial solar survey: supply, existing generation, inverter reference numbers and whether export needs limiting. Design tools help here (see solar design software for UK installers), and so does buying compliant kit from the right UK solar wholesalers. The ENA guide also notes customers need an MCS-certified installer to claim the Smart Export Guarantee; our MCS certification guide for installers covers it.

Once you can take on bigger connections, the bottleneck is usually finding the work. Our guide on how to get commercial solar leads compares nine channels, and how to sell commercial solar covers closing. Solar Surveys UK books qualified commercial solar survey appointments with business owners for UK installers: you pay per booked appointment, with no retainer (see what commercial solar leads cost and why booked surveys beat form fills).

G98: FAQ