G98 vs G99 for a commercial battery: which route is yours?

“Is a business battery G98 or G99?” is one of the first questions on any project, and the answer decides whether you need the network operator’s approval before a single cabinet is bolted down. The line is simple to state and easy to cross by accident.

The line: 16 A per phase

The Energy Networks Association’s Distributed Generation Connection Guide (March 2025) treats electricity storage as generation. Under it, a Type A power generating module above 16 A per phase, and below 1 MW, falls under G99. At or below 16 A per phase, the lighter G98 route applies: connect, then notify.

At 230 V per phase, that works out as roughly:

Supply	16 A per phase is about	Example
Single-phase	3.68 kW	A 3 kW battery inverter draws 13.0 A: under the line
Single-phase	3.68 kW	A 5 kW inverter draws 21.7 A: G99 Type A
Three-phase	11 kW	A 10 kW inverter draws 14.5 A per phase: under the line
Three-phase	11 kW	A 15 kW inverter draws 21.7 A per phase: G99 Type A

Those are arithmetic, not a determination: the operator decides from your application, and the figure that matters is the registered capacity of the module as the equipment is registered, not the label on the box. The checker on the G99 application page does the same sum.

How adding solar tips a battery into G99

The sum is over the generation and storage at the premises, not per unit. The ENA guide notes that when a battery is used with solar to offset consumption, the total connected generation is likely to be above 16 A per phase, so G99 applies. A 10 kW three-phase battery on its own is G98 territory by this arithmetic; add 80 kWp of PV on the same premises and the site is at about 90 kW combined, which is G99 Type A. That is the usual way a “small battery add-on” becomes a G99 project.

Type A is most business batteries

Once you are over the G98 line, G99 groups what you are building by size. Type A runs from 0.8 kW to under 1 MW; Type B from 1 MW to under 10 MW; Type C from 10 MW to under 50 MW; Type D from 50 MW (or any connection at 110 kV or above). A 100 kW three-phase battery is about 145 A per phase: comfortably G99 Type A. A 1 MW battery is Type B, which changes the whole shape of the project: the standard application form, network studies, a draft Power Generating Module Document and a Final Operational Notification, as set out on the G99 application page.

What changes between the routes

• Approval. G98: connect, then notify. G99: apply before anything is installed; the operator assesses the effect on its network and issues a connection offer.
• Forms. G99 Type A below 17 kW single-phase or 50 kW three-phase can use a simplified application form; larger systems use the ENA standard application form.
• Time. The operator’s quotation clock for a G99 connection is 45 working days at low voltage and 65 at high voltage when it does all the work (30 and 50 working days if an independent connections provider does the contestable part). Our programme guide shows where that sits in a whole installation.
• Commissioning. For Type A, the Installation Document reaches the operator within 28 days of commissioning (or on the day if the operator witnesses). See commissioning.

Two cases that need the operator’s view early

If the battery is meant to keep the site running in an outage (island mode), the fast-track route for some domestic-scale storage does not apply, and the standard G99 process does; G99 requirements apply to island-capable generation. And if your connection is already tight, a G100 export and import limitation scheme can let a battery connect inside the existing agreed capacity, if the operator accepts it.

Terms on the quote you do not recognise? The G99 jargon buster defines them, and how long a G99 application takes sets out the operator’s clocks.

Next step

Find your network operator first: the who is my DNO guide explains how to read your MPAN. Then work through the G99 application guide. If you want to talk it through, send an enquiry; we reply by email, and this site is not an installer.