What are G98 and G99?
G98 and G99 are UK grid connection standards published by the Energy Networks Association (ENA). They define the rules for connecting small-scale energy equipment – including home batteries, solar panels, and generators – to the electricity distribution network. G98 covers smaller systems (up to 3.68kW per phase). G99 covers everything above that threshold.
These standards exist to protect the stability of the local electricity grid. Every battery inverter that can export or import power has the potential to affect voltage and frequency on the grid. The DNO (Distribution Network Operator) needs to know what is connected so they can manage the network safely.
G98 vs G99 at a glance
G98
Inverter limit: ≤ 3.68kW (single phase)
Process: Post-installation notification
Timeline: Installed same day, notified after
Approval needed? No
Can be refused? No (notification only)
Who handles it? Your installer
G99
Inverter limit: > 3.68kW (single phase)
Process: Pre-installation application
Timeline: 4–12 weeks for approval
Approval needed? Yes
Can be refused? Yes
Who handles it? Installer applies, DNO decides
Does battery capacity affect G98 or G99 classification?
No. G98 and G99 classification is based entirely on the inverter power rating (measured in kW), not the battery storage capacity (measured in kWh). You can install a 20kWh battery and still qualify for G98, as long as the inverter is rated at 3.68kW or below. The inverter rating determines the maximum instantaneous power flow – the battery capacity determines how long it can sustain that flow.
This distinction matters when choosing a system. Some manufacturers sell large batteries with large inverters, pushing you into G99 territory. Others – including the units Habo supplies – pair larger batteries with sub-3.6kW inverters specifically to keep installations under the G98 threshold.
Why does G98 matter for homeowners?
The practical impact is straightforward. A G98-compliant system can be installed and connected to the grid in a single visit. Your installer completes the work, commissions the system, and submits a notification to the DNO. You start saving money the same day.
A G99 system requires you to wait for DNO approval before installation can begin. This can take anywhere from four weeks to three months, depending on your DNO and the local grid conditions. If the grid in your area is already congested, the application may be refused entirely – meaning you have paid for equipment you cannot connect.
The 3.68kW threshold explained
The 3.68kW figure for single-phase connections comes from the 16A per phase current limit. On a standard UK single-phase supply at 230V, 16A equates to 3.68kW (230V × 16A = 3,680W). This is the maximum power the DNO allows to flow without a detailed engineering assessment.
For three-phase supplies, the G98 limit is 11.04kW total (3.68kW per phase × 3 phases). Three-phase supplies are less common in UK residential properties but are found in some larger or newer homes.
What if I want a bigger inverter?
If you need an inverter rated above 3.68kW (single phase), you will need a G99 application. Your installer submits the application to your local DNO, who will assess whether the grid can support the additional capacity. Common reasons for needing a larger inverter include wanting to charge an EV and battery simultaneously, or having a high-demand household with large instantaneous loads.
In most cases, a sub-3.68kW inverter is more than sufficient for residential battery storage. A 3.6kW inverter can charge a 10kWh battery from empty to full in under three hours during the off-peak window – comfortably within the five-hour overnight charging period offered by most time-of-use tariffs.
Which DNO covers my area?
The UK has six licensed DNO groups operating across fourteen regions. You can find your DNO by entering your postcode on the Energy Networks Association website. The main groups are UK Power Networks (South and East England), Western Power Distribution (now National Grid Electricity Distribution, covering the Midlands and South West), Scottish Power Energy Networks, Northern Powergrid, Electricity North West, and SSE Networks.
Each DNO has slightly different processes for G98 notification and G99 applications, but the core rules are the same across the UK.
What does your installer need to do?
For a G98 installation, your installer completes a commissioning form (known as an ENA Engineering Recommendation G98 Form A) and submits it to the DNO within 28 days of installation. This form confirms the equipment details, the rated power, and the installation address. No action is required from you as the homeowner.
For a G99 installation, the installer submits an application form before any work begins. The DNO may request additional information, conduct a grid study, or impose connection conditions. Only once approval is received can the installation proceed.
Habo's approach to G98 compliance
Every Habo battery system uses an inverter rated below 3.6kW. The EcoFlow STREAM AC 5000 lists a maximum grid-tied output of 3,000W (EcoFlow UK specs). This is a deliberate design choice. Staying under the G98 threshold keeps each installation on the simpler post-install notification route, rather than a pre-approval G99 application.
A 3.6kW inverter paired with a 10–12kWh battery delivers the ideal balance for most UK homes. It charges the battery fully during a five-hour off-peak window, discharges at a rate that covers typical evening consumption, and keeps the installation process fast and straightforward. For help choosing the right capacity, see our guide on what size battery you need. For a full overview of how a battery system works, see home battery storage systems explained.
Keep an eye on UK battery prices
Leave your email for occasional updates on UK home battery prices, tariff changes and the 0% VAT deadline. No spam, unsubscribe any time.
Thanks, you're on the list.
Simple battery, simple install
Electrician-wired EcoFlow STREAM from £2,499. Habo will try to serve anyone who registers in an area where we have an electrician. Nothing to pay today.
Join the waitlist