DNO, G98 and G99 for home solar
A practical guide to the UK grid connection paperwork behind domestic solar, batteries, G98, G99 and the 3.68kW per phase threshold.
Key takeaways
- G98 covers small compliant generation up to 16A per phase, which is 3.68kW single phase.
- G99 applies above that threshold or when a system doesn't meet G98 requirements.
- The inverter/export capacity is the key issue, not simply the number of panels.
Who the DNO is
Your Distribution Network Operator, or DNO, owns and manages the local electricity network. They aren't usually your energy supplier. If you connect solar or battery equipment that can operate in parallel with the grid, the DNO needs to know about it.
For normal homeowners, your installer should handle the paperwork. It's still worth understanding the terms because they affect quote design, export limits and install timing.
G98 in plain English
The Energy Networks Association Distributed Generation Guide describes G98 for single premises as generation with combined registered capacity no higher than 16A per phase. That works out as 3.68kW on a single-phase supply or 11.04kW on a three-phase supply.
A 4kW solar array can still be paired with a 3.68kW inverter. The panels may have a higher peak rating than the inverter, but the grid-facing output is what matters for the G98 threshold.
When G99 comes in
National Grid's guidance says G99 applies where generation or storage is rated above 16A, which is 3.68kW per phase, or where the system doesn't meet the current G98 requirements.
G99 isn't automatically bad. It just means the DNO assesses the connection before the system is connected. Some homes get approved for higher export. Some get an export limit. A well-designed system can still make financial sense with a limit.
Questions for your quote
Ask your installer what inverter capacity they're proposing, whether the system is G98 or G99, and whether any G100 export limitation is being used. If a battery is included, ask whether the combined inverter arrangement changes the DNO route.
Don't confuse kW and kWh. kW is power at a point in time. kWh is energy over time. DNO limits are usually about power capacity, while your annual savings are based on kWh generated, used and exported.
- What is the inverter AC output?
- Is the system G98, G99 or G99 fast track?
- Is export limited, and if so to what kW?
- Will the DNO evidence be included in the handover pack?
Sources checked
- Energy Networks Association Distributed Generation GuideG98 and G99 connection process guidance.
- National Grid G99 connection proceduresPlain guidance on when G99 applies.