G98 and G99 determine how a solar-panel, battery-storage or other electricity-generating system can connect to the local electricity network.
The basic difference is straightforward:
- G98 normally allows a qualifying smaller system to be installed and then notified to the Distribution Network Operator.
- G99 normally requires an application and a connection decision before the system is connected.
- The usual dividing line is 16A per phase, equivalent to 3.68kW on a single-phase supply.
- The decision is based on the complete installation’s registered AC capacity, not simply the number or combined wattage of the solar panels.
Battery inverters, existing solar equipment and export-limitation controls can all affect the correct route.
Regional note
This guide primarily covers England, Scotland and Wales. Northern Ireland uses G98/NI, G99/NI and the NIE Networks connection process.
G98 or G99: the quick answer
A solar installation may qualify for G98 when:
- Its aggregate registered capacity is no more than 16A on each phase.
- The generating equipment is fully type tested for the proposed configuration.
- It connects to the low-voltage network.
- It meets all the relevant installation and protection requirements.
G99 will normally apply when:
- Registered capacity exceeds 16A on any phase.
- Multiple inverters take the combined capacity above the G98 threshold.
- The equipment or configuration does not meet the conditions for G98.
- Solar and AC-coupled battery storage have a combined output above the threshold.
- The DNO needs to assess a larger or more complex connection before it is made.
A larger system restricted to exporting 3.68kW does not automatically become a G98 installation. It may still require a G99 application and a G100-compliant export-limitation scheme.
G98 vs G99 at a glance
| Question | G98 | G99 |
|---|---|---|
| Typical capacity | Up to and including 16A per phase | Above 16A per phase or outside the G98 conditions |
| Single-phase equivalent | Up to 3.68kW | Normally above 3.68kW |
| Three-phase equivalent | Up to 11.04kW when appropriately distributed | Above 16A on one or more phases |
| DNO involvement | Normally notified after commissioning | Normally assessed before connection |
| Equipment | Fully type-tested G98 equipment | Equipment meeting the relevant G99 requirements |
| Network assessment | Usually a simplified process | Individual assessment may be required |
| Export limiting | Not necessarily required | G100 may form part of the approved design |
| Battery storage | Must be included where it adds generating capacity | Common for combined solar-and-storage installations |
| Possible outcome | DNO records the qualifying installation | Approval, conditions, an export limit, network work or a revised proposal |
What are G98 and G99?
G98 and G99 are Engineering Recommendations covering electricity-generating equipment that operates in parallel with the public distribution network.
They help network operators ensure that solar inverters, batteries and other generators:
- Disconnect safely during a power cut.
- Operate within permitted voltage and frequency limits.
- Do not create unacceptable voltage rise or power-quality problems.
- Use suitable protection settings.
- Can be taken into account when the local network is operated and upgraded.
The organisation responsible for the local electricity network is the Distribution Network Operator, normally shortened to DNO.
- DNO
- Owns and operates the local cables, substations and transformers.
- Your supplier
- Bills you for imported electricity and may pay you for exported electricity.
- Your MCS contractor
- Designs and installs the solar system and undertakes the appropriate DNO process.
- Energy Networks Association
- Publishes the common engineering recommendations and equipment registers used by network operators.
Your DNO is not the same as your electricity supplier.
G98 and G99 are not planning permissions, export tariffs or replacements for an MCS certificate.
Where does the 3.68kW G98 limit come from?
The G98 threshold is up to and including 16A per phase.
Using the UK’s nominal voltage of 230V:
230V × 16A = 3,680W
That produces the familiar 3.68kW single-phase limit.
For an appropriately distributed three-phase installation:
3 × 230V × 16A = 11,040W
This gives a potential total of 11.04kW across three phases.
Most UK homes have a single-phase electricity supply, but some larger homes and commercial properties have three-phase connections.
A three-phase supply does not automatically guarantee approval for an 11.04kW installation. The generating equipment must remain within the applicable limit on every phase and meet the other G98 conditions.
Panel capacity, inverter capacity and export limits are not the same
- Solar-panel capacity
- The combined DC rating of the panels, normally expressed in kilowatt-peak, or kWp. For example, ten 450W panels form a 4.5kWp array. This describes the panels' rated output under standard test conditions. It does not directly state how much AC power the installation can provide to the home or network.
- Inverter AC capacity
- The inverter converts the panels' DC electricity into AC electricity. Its AC output may be lower than the combined panel capacity. This is common because panels rarely operate continuously at their full laboratory rating.
- Registered capacity
- The generating capacity declared for the network-connection assessment. For a typical solar installation, the inverter's approved AC output is a central part of this figure. Where several generating units are connected at one property, their capacities may need to be assessed together.
- Maximum export capacity
- The greatest amount of power the installation is permitted to send through the grid connection. It can be lower than the installation's registered capacity if an approved export-limitation scheme is used.
Several different power figures appear on solar quotations and equipment datasheets. Confusing them can lead to the wrong conclusion about whether G98 or G99 applies.
The question to ask your installer: What are the installation’s aggregate registered capacity per phase and its proposed maximum export capacity?
Can a G98 system have more than 3.68kWp of solar panels?
Example
- Panel-array capacity: 5kWp
- Inverter registered AC capacity: 3.68kW
- Electricity supply: single phase
- Equipment: fully type tested for the proposed configuration
This system may qualify for G98 because the relevant registered AC capacity remains within 16A, even though the panels have a combined rating of 5kWp.
Yes. G98 does not impose a simple 3.68kWp limit on the solar panels themselves.
The inverter may occasionally limit, or clip, panel production when available DC power exceeds what it can convert. However, panel output varies with sunlight, temperature, roof direction and shading, so a larger panel array can still improve annual generation.
The array must remain within the inverter manufacturer’s permitted input-voltage, current and power limits. Read more in our guide to solar inverter sizing.
How battery storage affects G98 and G99
Battery capacity is normally expressed in kilowatt-hours. This tells you how much energy the battery can store, not how much AC power it can deliver at one moment.
A 10kWh battery could use a 3kW, 5kW or differently rated inverter. The inverter arrangement and discharge capability, not the battery’s kWh capacity alone, affect the DNO assessment.
AC-coupled batteries
An AC-coupled battery has an inverter separate from the solar inverter.
For example:
- Solar inverter: 3kW
- Battery inverter: 3kW
- Potential aggregate AC output: 6kW
On a single-phase connection, 6kW exceeds 16A. The installation would not follow the ordinary G98 route simply because each individual inverter is below 3.68kW.
A qualifying Small Generation Installation procedure may be available, potentially combined with an approved export limit, but the installer must identify the correct route.
DC-coupled batteries and hybrid inverters
A DC-coupled battery normally shares a hybrid inverter with the solar panels.
If the shared inverter has a qualifying registered capacity of 3.68kW, the panels and battery do not necessarily create two separate 3.68kW generating units. The inverter controls the combined AC output.
The precise assessment depends on:
- The inverter’s registered capacity.
- Its type-test registration.
- The manufacturer-approved configuration.
- Whether solar and battery can produce AC output independently.
- Any secure output restriction.
- The proposed export capacity.
Adding a battery to existing solar
An installer should not assess a new battery in isolation.
They need to check:
- What solar equipment is already connected.
- What capacity the DNO currently has recorded.
- Whether the battery uses a separate inverter.
- The aggregate AC capacity after the upgrade.
- Whether backup operation changes the applicable process.
- Whether a G100 export limit is proposed.
Planning the solar and battery together can avoid having to revisit the connection design shortly after the original installation.
G98 or G99? Common home-solar examples
| Proposed installation | Likely route | Reason |
|---|---|---|
| 4kWp of panels with a qualifying 3.68kW inverter | G98 may apply | Registered AC capacity remains within 16A |
| 6kWp of panels with a qualifying 3.68kW inverter | G98 may apply | Panel kWp can exceed inverter AC capacity |
| Unrestricted 5kW single-phase inverter | G99 | Registered capacity exceeds 16A |
| 5kW inverter with a 3.68kW export limit | Usually G99 with G100 | Export capacity and registered capacity are different |
| 3kW solar inverter plus 3kW AC battery inverter | G99 or an eligible simplified route | Aggregate AC output exceeds 16A |
| Qualifying 3.68kW hybrid inverter serving solar and battery | G98 may apply | The shared maximum AC capacity remains within the threshold |
| Existing 3kW solar inverter plus a new 2kW solar inverter | G99 | Existing and new generation are assessed together |
| Additional panels behind an unchanged 3.68kW inverter | The existing connection route may remain | Registered AC capacity may not change |
| Balanced 10kW three-phase installation | G98 may apply | Output can remain below 16A on each phase |
Can an export limit keep a larger system within G98?
Not automatically.
An export limit controls how much power crosses from the property into the distribution network. It does not necessarily change what the installed equipment is capable of generating.
This creates an important distinction between three arrangements.
- Manufacturer-restricted registered capacity
- Some equipment may have its output securely restricted by the manufacturer to a lower registered capacity. For that restriction to be recognised, it must be part of the approved product arrangement and must not be something the homeowner can easily change, defeat or override. The declared configuration and type-test entry need to support it, and the DNO may need to agree how it is treated.
- User or installer export setting
- Many inverters allow an export value to be selected in their settings. A normal adjustable setting is not automatically equivalent to a permanently restricted registered capacity. It may be changed, reset or lost following equipment replacement or software changes.
- G100 export-limitation scheme
- A G100-compliant scheme monitors power at the grid connection and controls the generating equipment so export remains within the agreed maximum.
Example
A larger solar-and-battery installation might have:
- Registered capacity above 3.68kW
- G99 connection approval
- G100-compliant export control
- Maximum permitted export of 3.68kW
The home may still be able to use more than 3.68kW internally or direct available power into a battery, depending on the approved design. When household consumption is low and the battery cannot absorb more energy, the control system reduces generation to keep export within the agreed limit.
An export-limited system can therefore remain useful, but it should not be described as ordinary G98 merely because its export is capped at 3.68kW.
What happens under G98?
The installer checks the supply and equipment
Electricity supply, existing generation and equipment type testing.
The system is designed within the G98 conditions
Aggregate registered capacity, protection and configuration.
The equipment is installed and commissioned
To the approved design.
The installer notifies the DNO within 28 days
After commissioning.
The DNO records the installation
Against the property MPAN.
The homeowner receives or requests the acknowledgement
Keep this with the handover documents.
G98 is often described as “fit and notify”. That does not mean the connection is unregulated or that any small inverter can be fitted.
The system still needs appropriate protection, isolation, labelling, commissioning and type-tested equipment.
Special rules apply where one installer is connecting generators at multiple properties within the same local area over a short period. That does not normally change the homeowner’s design decision, but it can change when the installer must contact the DNO.
What happens under G99?
The proposed solar-and-battery system is designed
Including any battery inverter and existing generation.
The installer identifies the appropriate G99 route
Full application or a simplified Small Generation Installation route.
Technical information and an operating diagram are submitted
To the DNO.
The DNO assesses the proposed connection
Against local network conditions.
The DNO issues a decision or asks for changes
Approval, conditions, a reduced export offer or a revised design.
The system is installed and configured
In accordance with the accepted design.
Commissioning documentation is submitted
Confirming what was actually installed.
The homeowner receives the final DNO records
Retain these permanently.
The application should be made early enough that the connection decision can influence the design. Buying equipment before the decision could leave the homeowner with an inverter that cannot be used at its intended capacity.
Is there a faster G99 route for home solar and batteries?
Simplified Small Generation Installation routes exist for certain smaller, fully type-tested generation and storage arrangements.
Eligibility can depend on:
- The capacity of each generating unit.
- The aggregate capacity of the complete installation.
- Existing solar or storage at the property.
- Whether individual outputs are securely restricted.
- The proposed maximum export capacity.
- Whether a G100-compliant export limitation scheme is included.
- The equipment’s type-test status.
- The way the battery and solar operate together.
Some simplified configurations can follow a notify-after-connection process, while others need approval before connection.
“Fast track” should therefore not be treated as a universal permission to install first. Ask the installer to identify the exact route and whether written DNO acceptance is required before commissioning.
Can a G99 application be refused?
A DNO does not have to accept every proposal exactly as submitted.
The local cables and transformer must keep network voltage and other operating conditions within permitted limits. The result can be affected by the property’s location, the existing level of generation nearby and the condition of the local network.
The DNO may:
- Approve the requested capacity.
- Approve the system with technical conditions.
- Offer a lower maximum export capacity.
- Require a G100 export-limitation scheme.
- Ask for different protection settings.
- Suggest a revised inverter or phase arrangement.
- Identify necessary network reinforcement.
- Decline the original proposal where it cannot be accommodated safely.
A reduced export offer does not necessarily prevent the larger system from being worthwhile. It may still provide greater power for the home, charge a battery faster or reduce inverter clipping. The value depends on how the approved controls affect generation, consumption and storage.
Does G99 mean you need three-phase electricity?
No. A G99 installation can be connected to either a single-phase or three-phase supply, subject to the DNO’s decision.
Three-phase power may be considered when:
- The proposed generating capacity is too high for one phase.
- Output can be distributed more evenly across the network.
- The home is undergoing a wider electricity-supply upgrade.
- Large electrical loads also need to be accommodated.
A three-phase upgrade can involve additional cost and electrical work. It should not be recommended solely because an installer prefers a larger inverter.
Is it worth applying for G99?
G98 is not automatically the best choice simply because it is quicker, and G99 is not automatically better because it permits a larger system.
A G98 design may be appropriate when:
- A 3.68kW inverter suits the home’s expected demand.
- Additional inverter clipping is limited.
- No major solar or battery expansion is planned.
- The simpler connection route keeps the project on schedule.
- The larger system’s extra annual value would be modest.
G99 may be worth considering when:
- The roof can accommodate a materially larger solar array.
- A larger inverter would reduce meaningful generation losses.
- Higher battery-discharge power would help meet household demand.
- Additional solar or storage is planned.
- The home’s electricity use is expected to increase.
- Greater permitted export could produce worthwhile income.
- The owner wants the connection planned around a complete future system.
Compare the annual difference rather than focusing only on the inverter’s maximum rating. A larger inverter may provide little extra energy on some roofs but make a meaningful difference on a large, unshaded south-facing array.
Plan for future panels, batteries, EVs and heat pumps
It is sensible to describe your longer-term plans before the installer prepares the connection application.
That may include:
- Adding a home battery.
- Installing panels on another roof.
- Replacing the inverter with a larger model.
- Adding a second inverter.
- Installing an EV charge point.
- Moving to vehicle-to-home or vehicle-to-grid equipment.
- Installing a heat pump.
- Adding backup-power capability.
- Upgrading to a three-phase supply.
EV chargers and heat pumps normally consume electricity rather than generate it, so they do not simply count towards the G98 generation threshold. However, they affect the wider electrical design, supply capacity and way electricity flows around the home.
Ask the installer:
What solar, battery and export capacity will the DNO have recorded after this installation, and will that arrangement support the upgrades we are likely to make later?
What G98 or G99 paperwork should you receive
Your handover documents should identify exactly what was connected and what the DNO has accepted or recorded.
Keep copies of:
- The DNO acknowledgement, approval or connection offer.
- The DNO application or reference number.
- The approved registered capacity.
- The approved maximum export capacity.
- Details of any G100 export-limitation scheme.
- The inverter’s type-test reference.
- The system’s single-line or operating diagram.
- Installation and commissioning records.
- The MCS certificate.
- The electrical installation certificate.
- Equipment datasheets and warranties.
An electricity supplier may ask for a “G98 certificate” or “G99 certificate”. In practice, it may be looking for the DNO acknowledgement or acceptance letter confirming that the connection has been properly recorded.
These records may also be needed when:
- Applying for a Smart Export Guarantee tariff.
- Changing export supplier.
- Adding solar panels or batteries.
- Replacing an inverter.
- Selling the property.
- Investigating a difference between the installed equipment and the DNO record.
What if your solar system has no DNO paperwork?
Start by checking the original handover folder, emails from the installer, emails or letters from the DNO, documents supplied by a previous homeowner, and the MCS certificate and electrical paperwork.
If no DNO acknowledgement or approval can be found:
Locate the property's MPAN
From an electricity bill.
Identify the local Distribution Network Operator
This depends on the property's region, not the electricity supplier.
Ask the DNO what it has recorded
Generation and storage registered at the address.
Compare the DNO record with the equipment installed
Inverter model, registered capacity and export limit.
Ask a competent solar installer to investigate any discrepancy
Before making changes.
Resolve the existing record before adding equipment
Do not add another inverter or battery until the position is clear.
Important
Do not submit a duplicate application without first establishing what the DNO already holds. An older installation may have been registered under the previous G83 or G59 recommendations and could still have a valid historic record.
Does plug-in solar use G98 or G99?
Compliant plug-in solar products became legal to buy and use in Great Britain on 27 August 2026.
Under the interim product specification, a qualifying plug-in solar product:
- Has a maximum apparent power of no more than 800VA.
- Must comply with the applicable product and electrical-safety requirements.
- Uses the updated G98 framework for connecting plug-in microgeneration.
- Must be supplied as a complete compliant product rather than assembled from unrelated parts.
The initial specification does not cover:
- Plug-in battery systems.
- Plug-in solar products incorporating battery storage.
- Conventional rooftop PV installations designed under the normal fixed-wiring requirements.
- Plug-in generation using energy sources other than solar PV.
An 800VA plug-in product is far below the normal 16A G98 threshold, but it still needs to comply with its specific product, installation and registration requirements.
G98 and G99 in Northern Ireland
Northern Ireland uses regional versions of the engineering recommendations:
- G98/NI
- G99/NI
NIE Networks operates the relevant registration and connection processes.
Although the familiar 16A-per-phase distinction remains important, Great Britain’s forms, procedures and connection guidance should not automatically be applied to a Northern Ireland installation.
Homeowners in Northern Ireland should ask the installer to confirm the applicable NIE Networks route and any application charges before accepting the quotation.
Questions to ask before accepting a solar quote
Ask the installer:
- Is my electricity supply single phase or three phase?
- What is the proposed panel-array capacity in kWp?
- What is the inverter’s registered AC capacity?
- What existing solar or storage has been included in the assessment?
- Does the battery share the solar inverter or have a separate inverter?
- What is the aggregate registered capacity per phase?
- Are you using G98, G99 or a Small Generation Installation route?
- Is G100 export limiting required?
- What maximum export capacity are you requesting?
- Will written DNO acceptance be obtained before the system is connected?
- Are application and administration charges included in the quotation?
- What happens if the requested capacity is not accepted?
- Could the proposed design restrict future solar or battery expansion?
- Which DNO documents will I receive at handover?
A good quotation should make the proposed connection arrangement clear rather than describing the project simply as “G98” or “G99”.
Frequently asked questions
What is the main difference between G98 and G99?
G98 normally provides a fit-and-notify route for fully type-tested generation up to and including 16A per phase. G99 normally requires an application and DNO decision before connecting generation outside those conditions.
Is G98 limited to 3.68kWp of solar panels?
No. The panel array can have a higher DC capacity than 3.68kWp. The inverter’s registered AC capacity and the complete generating arrangement determine whether G98 may apply.
Can a 5kW inverter be used under G98?
Only if the specific equipment has a qualifying manufacturer-secured registered capacity within the G98 limit and the complete configuration meets the relevant requirements. An ordinary user-adjustable 3.68kW export setting is not necessarily sufficient.
Does a home battery count towards the G98 limit?
It can. A separate AC-coupled battery inverter may add to the aggregate generating capacity. A battery sharing a hybrid inverter with the panels may be assessed differently because the equipment shares one controlled AC output.
Does a 3.68kW export limit make a system G98?
Not automatically. A larger system may still require G99 approval, with G100 used to maintain the agreed export limit.
How long does a G99 application take?
There is no single universal period for every domestic application. Simplified routes may be decided relatively quickly, while full assessments can take longer. Incomplete information, local constraints or reinforcement requirements can extend the process.
Does a G99 application cost money?
DNO and installer charges vary by route and region. A straightforward application may have little or no direct DNO charge in some areas, while technical studies, installer administration or network reinforcement can create costs. Obtain the position in writing before committing to the installation.
Can the DNO refuse a G99 application?
The DNO can decline the original proposal if it cannot be safely accommodated. It may instead offer a reduced export capacity, request a revised design or identify necessary network work.
Does G99 require three-phase power?
No. G99 systems can connect to single-phase supplies. Three-phase power may be considered for larger installations or where it helps distribute the output.
Can I add panels without changing the DNO connection?
Possibly. Adding panels behind the same inverter may not change the registered AC capacity, but the inverter’s input limits, system design and records must still be checked. Adding another inverter is more likely to change the connection assessment.
Who submits the G98 or G99 paperwork?
For an MCS installation, the MCS contractor should undertake the relevant G98 or G99 notification or application. The homeowner should still receive and retain the resulting documentation.
Is an MCS certificate the same as G98 or G99 approval?
No. MCS certification concerns the installed system and the contractor’s certification framework. G98 and G99 concern connection to the distribution network.
Is G99 approval the same as an export tariff?
No. The DNO approves or records the network connection. An electricity supplier separately determines whether the installation qualifies for its export tariff.
Does a completely off-grid system need G98 or G99?
A genuinely off-grid system that never operates in parallel with the public distribution network would not normally use the G98 or G99 connection process. Systems capable of grid-parallel operation need appropriate assessment even if they are intended to export very little.
The bottom line
G98 versus G99 cannot always be decided from the number of panels or the amount of electricity you expect to export.
The three most important points are:
- Use the complete installation’s aggregate registered AC capacity, not panel kWp alone.
- Include existing solar and any battery inverter in the assessment.
- Obtain any required G99 decision before committing to the final system design.
A well-planned connection should meet today’s requirements while leaving sensible room for future solar panels, battery storage and changing household electricity use.
Related guides
Sources and further information
- MCS MIS 3002 Issue 6.0 – Solar PV Systems
- Energy Networks Association Distributed Generation Connection Guide
- National Grid G98 connection procedures
- National Grid G99 connection procedures
- National Grid export-limitation guidance
- NIE Networks Distribution Code and G98/NI and G99/NI information
- GOV.UK plug-in solar announcement
- Great Britain plug-in solar interim product specification