G98 vs G99: Which Standard Applies to Your Solar System?

For most UK homeowners, the rule is straightforward: G98 covers solar systems up to 3.68 kW per phase, while G99 applies to anything above this limit. In practice, the key figure is usually the inverter output or agreed export capacity, not only the total size of the panels on your roof.

Your Distribution Network Operator (DNO) needs this information to assess potential export to the local grid. If G99 applies, approval is required before installation or commissioning, which may affect timescales. Understanding G98 vs G99: which standard applies to your solar system? helps you compare quotes and avoid connection delays.

Alt: G98 vs G99: which standard applies to your solar system?

Which standard applies to your solar system?

• G98 applies to small domestic solar systems up to 16A per phase (typically 3.68kW on a single-phase UK home supply).
• G99 applies when the system exceeds this limit and requires a more detailed grid connection assessment.
• Most home solar installations are designed to stay within G98 limits or use export limiting to comply with permitted export levels.

G98 and G99 in the UK solar connection process

G98 and G99 are UK grid connection standards used by Distribution Network Operators. A DNO application for solar panels is the process your installer uses to notify or seek approval from the network operator responsible for the cables in your area.

What is G98 for UK solar installations?

G98 is the connection route for smaller grid-connected generation systems up to 16A per phase. It is commonly used for domestic solar PV, small hybrid inverter systems, and standard home battery installations that stay within the export limit.

What is G99 for UK solar installations?

G99 applies to larger generation systems exceeding 16A per phase or export capacities beyond G98 limits. It provides the required connection route for projects with higher proposed generation or export capability.

Why the DNO needs to know

DNO approval ensures solar exports do not affect network safety or stability. It helps manage voltage levels, grid capacity, protection systems, and safe connections, preventing issues such as local overloading or excessive voltage rise.

G98 vs G99 at a glance

The fastest way to understand G98 vs G99 is to compare the connection rules side by side. The main difference is whether your installer can notify after installation or must wait for approval first.

G98 is generally a simpler connection route for smaller domestic installations. G99 involves more technical assessment and can affect the installation date. That does not mean G99 is bad. It simply means the DNO must confirm that the local grid can safely accept the higher export capacity.

How does the 3.68 kW per phase limit work?

The 3.68 kW per phase solar limit is the main decision point for many UK homeowners. It comes from the 16A-per-phase threshold used in the grid connection rules.

The 16A calculation

The calculation is straightforward: 230V x 16A = 3,680W, or approximately 3.68 kW.

That is why a 3.6 kW inverter is so common in UK home solar quotes. It sits just under the G98 single-phase threshold.

Three-phase properties

Three-phase properties can connect more capacity under the same 16A-per-phase rule. Instead of one phase at 3.68 kW, there are three phases. That gives a G98 threshold of 3.68 kW x 3, or 11.04 kW in total, assuming the system is correctly balanced and compliant.

Panel capacity versus inverter capacity

Panel capacity and solar inverter output are not the same thing. A 5 kWp solar array with a 3.68 kW inverter may still fall under G98 because the inverter controls the AC output.

A 5 kWp array with an unrestricted 5 kW inverter on a single-phase supply will usually require G99. A 5 kW inverter export-limited to 3.68 kW may remain within G98, depending on the system design and DNO requirements.

G98 standard: install first, notify after

For G98 solar panels, the process is designed to be practical for smaller systems. Your installer normally handles the paperwork and notifies the DNO after the system has been commissioned.

• Systems covered by G98: G98 typically applies to small domestic solar PV systems, hybrid inverters within the 3.68kW single-phase limit, and some three-phase systems below 11.04kW. Solar-plus-battery systems may also qualify if export capacity stays within limits.
• G98 notification process: After installation and commissioning, the installer submits the G98 notification to the DNO within 28 days. The DNO records the system details for network management, usually without causing delays for homeowners.
• Required information: Installers may need your MPAN, address, inverter details, export capacity, commissioning date, MCS details (if applicable), and supply type. Preparing these details helps speed up the process.

G99 standard: apply before you install

For G99 solar panels, the system is above the small-generation threshold, so the DNO must assess the proposed connection before installation or commissioning.

• Systems covered by G99: G99 usually applies to larger solar PV systems, commercial installations, multi-inverter setups, and battery systems exceeding the 16A per phase limit. It may also apply when combined solar and battery outputs exceed G98 export limits.
• G99 application process: The installer confirms system design and export capacity, prepares technical documents, and submits the application to the DNO. The DNO reviews grid capacity and technical compliance before approving, rejecting, or adding connection conditions.
• Timelines and outcomes: Approval may take several weeks or longer depending on network conditions. The DNO may require export restrictions, inverter adjustments, system redesign, reinforcement work, or reduced export capacity before connection.

Can export limiting or battery storage change the application route?

Design choices can affect whether a system follows G98, G99, or a faster limited-export route. Export limiting solar panels and battery systems can help larger installations stay within an agreed export level.

Export limiting in practice

Export limiting caps the electricity your system sends to the grid, often at 3.68 kW for single-phase homes. You can still use solar directly or charge a battery, but peak summer output may be curtailed if unused.

Battery storage and aggregate capacity

Battery storage affects the DNO route when it can export to the grid. Separate solar and battery inverters may raise total export capacity. Solar battery DNO approval is based on the full system design, not just battery kWh, because DNOs assess possible grid export.

Hybrid inverter systems

A DC-coupled or hybrid inverter system may remain within G98 if the inverter output or grid export is limited to the permitted level. This is common where homeowners want more panels and battery storage without increasing the maximum export beyond 3.68 kW on a single-phase supply.

When considering a home battery storage system, it is important to understand the connection method, grid requirements, and export capabilities before installation. 

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Before installation, homeowners should still confirm local grid connection requirements and the appropriate DNO process to ensure the system meets regional regulations.

A practical checklist before approving your solar quote

Before accepting a quote, make sure the connection route is clear. A good installer should explain whether your system is G98, G99, or designed with export limiting.

• Quote details to check: Verify inverter size, export limit, solar capacity, battery inverter capacity, system type, G98/G99 route, and export limiting compliance before approval.
• Questions for your installer: Ask about DNO paperwork, approval requirements, export limiting, potential conditions, redesign options, and written confirmation.
• Documents to keep: Store DNO confirmation, MCS certificate, inverter details, commissioning records, and export documents for future payments, warranties, upgrades, or property sales.

Conclusion

When comparing G98 vs G99: which standard applies to your solar system? the main factors are inverter export capacity, supply type, battery setup, and any export limit. In most UK homes with a single-phase supply, G98 normally applies when grid export is up to 3.68 kW per phase, while G99 is required above that threshold unless the system is designed or export-limited to stay within permitted limits. 

For three-phase properties, the G98 allowance can be up to 11.04 kW across all phases. Before installation, ask your installer to confirm the classification in writing to avoid delays and compare quotes accurately.

FAQ

Is the G98 limit based on solar panel size or inverter size?

The G98 limit is usually based on inverter AC output or export capacity, not simply the solar panel kWp. A 5 kWp panel array with a 3.68 kW inverter may be G98, while the same array with an unrestricted 5 kW inverter may need G99.

How long does a G99 application take?

A G99 application often takes several weeks, and longer where local grid capacity is constrained. Some smaller or fast-track cases may be quicker, while complex domestic or commercial systems can take months. Your installer should build this into the installation timeline.

Can export limiting keep my solar system under G98?

Yes, export limiting can sometimes keep a larger solar system within G98 by capping grid export at 3.68 kW on a single-phase supply. You may still use more energy on site or charge a battery, but excess generation may be curtailed when export reaches the cap.