G98 vs G99: The Difference for UK Home Batteries (2026)

What are G98 and G99?

A home battery counts here even if you have no solar panels. The ENA guide says DNOs treat electricity storage as generation when they assess the impact on their network, so storage has to meet G98 or G99 depending on its capacity (ENA Distributed Generation Connection Guide). The DNO is the company that runs the local wires, not the supplier that sends your bill.

G98 vs G99 comparison table

Going down the G99 route? Our G99 application guide for home batteries walks through the forms, what the DNO looks at and how to avoid delays.

The 3.68 kW threshold explained

The limit in G98 is written as a current: up to and including 16 A per phase. On a 230 V single-phase supply, 16 A works out at 3.68 kW (230 V × 16 A = 3,680 W). On a three-phase supply it is 11.04 kW in total. The ENA guide gives both figures and makes clear they apply to the total generating capacity at one property, not to each device (ENA G98 single premises guide).

For inverter-connected kit, the rating that counts is the inverter's continuous steady state rating. National Grid Electricity Distribution gives a worked example: a single-phase 4 kW inverter is 4,000 ÷ 230 = 17.39 A, just over the 16 A threshold, so it falls under G99 (NGED G99 connection procedures).

Does battery capacity affect G98 or G99?

This matters when you compare systems. A large battery behind a small inverter can stay inside G98. A smaller battery behind a bigger inverter can push you into G99. Always ask for the inverter's rated output, not just the kWh figure.

Already have solar panels? Adding a battery can mean G99

G98's 16 A limit is the total for the property. If you already have a solar inverter and add a battery inverter, the two ratings are added together. The ENA guide says that when storage is used alongside solar, the total is likely to be above 16 A per phase, so G99 applies (ENA Distributed Generation Connection Guide).

That is where the G99 fast track helps. Since November 2022, small installations that use fully type-tested inverters and stay within 32 A or 60 A per phase in total (depending on the category) can use a shorter application on Form A1-2 (ENA). Some categories need an export limitation scheme under EREC G100 that caps what the property can send to the grid (NGED fast track). The ENA guide also notes that storage designed to run in island mode during a power cut cannot use the fast track and goes through the standard G99 process (ENA guide).

How long does G99 approval take?

Under G98 there is no approval wait at all. Your installer can commission the system and notify the DNO afterwards, within the 28 days (ENA G98 guide). On the fast track, the planned commissioning date on the form has to be between 10 working days and three months after the application goes in (ENA). Installers can also apply through ENA Connect Direct, a single online form used by the UK's DNOs. It can auto-approve applications that pass its checks and sends the rest to a DNO connection engineer.

Which DNO covers my area?

The ENA's find my network operator tool tells you from your postcode, or from the Distributor ID at the start of the MPAN on your electricity bill. In England, Scotland and Wales you can also call 105 for free to reach your DNO. The six GB operators listed by the ENA are UK Power Networks, National Grid Electricity Distribution, Scottish and Southern Electricity Networks, SP Energy Networks, Northern Powergrid and Electricity North West (ENA). Each has its own forms and inboxes, but equipment connected to any of their networks has to comply with the same ENA G98 and G99 documents (SSEN).

What does your installer need to do?

For G98, the installer commissions the system and sends the DNO the Installation Document, Form B in Appendix 3 of EREC G98, no later than 28 days (including the day of commissioning) after commissioning (EREC G98 Issue 2). Some DNOs use their own version of the form. Manufacturers of G98 equipment have to lodge their declarations of compliance on the ENA LCT Register, so your installer can check the exact model (ENA). The older ENA Type Test Register closed in April 2024 and its data moved into Connect Direct (ENA guide).

For G99, the installer sends the application before any connection is made. The DNO may ask for more information, such as a schematic, type test certificates or details of an export limitation scheme, and you cannot connect until it confirms its assessment is complete (SSEN G99 fast track).

Where Habo's EcoFlow STREAM fits

Habo fits the 5 kWh EcoFlow STREAM, an all-in-one with the inverter in the unit. EcoFlow UK lists a maximum grid-connected output of 2,500 W for a single STREAM AC 5000, or 3,000 W when it is stacked with an Expansion Battery 5000, and 3,000 W for a single STREAM 5000 (EcoFlow UK STREAM AC 5000). All of those sit under the 3,680 W G98 line for a single-phase home, so one main unit on its own fits the G98 notify route. Your electrician still checks what else is already connected at the property, because the 16 A limit is a total. EcoFlow also says one system can link up to six main units (EcoFlow UK), so several units together could cross into G99.

EcoFlow says the STREAM must be hardwired into your consumer unit by a certified, registered electrician in the UK, and should not be plugged into a household socket to feed power in (EcoFlow UK). The electrician who wires it also sends the G98 notification. See our guide to UK home battery installation rules for the wiring side.

Best case, the 5 kWh STREAM at £2,499 fully installed saves up to about £450 to £530 a year on Octopus Go. Think of that as the interest you would earn on £2,499 in a savings account: about 18.1% to 21.1% a year (see how we worked it out, using Octopus Go 12M Fixed rates checked 15 October 2026). It assumes one full cycle every day, so real savings will be lower. For the full comparison, see home battery vs savings account. For help choosing a size, see what size battery you need.

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