When you’re considering solar panels for your home, you’ll probably come across terms like G98, G99, DNO approval and DNO letter. While these may sound complicated, they’re simply part of the process that ensures your solar PV system connects safely to the electricity grid.
At SolarTherm UK, we help homeowners throughout Essex, Kent, Suffolk, Hertfordshire and the wider South East and East Anglia navigate every stage of the installation process, including dealing directly with your local Distribution Network Operator (DNO).
This guide explains the difference between G98 and G99, what they mean for your installation and whether they’ll affect your project timeline.
What Does DNO Mean?
Before understanding G98 and G99, it’s important to understand the meaning of DNO. A Distribution Network Operator (DNO) owns and maintains the local electricity network that delivers power to your home.
Unlike your energy supplier, who sends your bills, your DNO is responsible for ensuring the local electricity network can safely handle electricity being exported from solar PV systems.
Whenever a new solar installation is connected to the grid, your installer must follow the relevant Engineering Recommendation issued by the Energy Networks Association. For most homeowners, this usually means either a G98 notification or a G99 application. The correct route depends on the size of your solar PV system.
What is G98?
G98 is the simpler notification process. It applies to smaller domestic solar systems where the inverter capacity is up to 3.68kW per phase. Rather than requesting permission before installation, your installer can usually install the system first and then notify the DNO afterwards. This makes installation faster and reduces paperwork for homeowners.
What is G99?
G99 applies when a solar installation is capable of exporting more electricity than the G98 limit allows. This generally means larger solar arrays, more powerful inverters, battery storage systems and three phase installations. Unlike G98, permission must be granted before installation begins. The DNO assess whether the local electricity network can safely accommodate the additional generation. Approval times can vary depending on workload and network complexity.
G98 vs G99: What’s the Difference?
The main difference between G98 and G99 is the generating capacity of the equipment being connected to the electricity network and the connection procedure that applies.
G98 is designed for qualifying, type-tested microgeneration equipment operating at up to 16 amps per phase on a low-voltage network. For a typical single-phase domestic installation, this equates to approximately 3.68kW of AC output. Eligible systems can generally be installed and commissioned before the required notification is submitted to the Distribution Network Operator (DNO).
G99 applies to generation equipment that does not qualify for the G98 process. The DNO will normally need to assess and approve the proposed connection before installation or connection proceeds.
| Feature | G98 | G99 |
|---|---|---|
| Main application | Qualifying, type-tested microgeneration | Generation equipment outside the G98 scope |
| Typical domestic threshold | Up to 16A per phase, approximately 3.68kW on single phase | Equipment exceeding the applicable G98 limits or otherwise outside its scope |
| Process | Connect and notify, where eligible | Apply for connection and obtain the required approval |
| Timing | Notification normally submitted within 28 days of commissioning | Approval normally required before the relevant installation or connection proceeds |
| DNO assessment | Checks compliance with the applicable requirements | May include a more detailed assessment of network capacity and connection conditions |
| Possible outcome | Notification recorded in accordance with the applicable process | Approval, export restrictions, additional conditions or network works |
Important: The 3.68kW figure refers to AC generation capacity per phase, not the total wattage of the solar panels. The applicable route must be confirmed against the complete installation design and current Engineering Recommendations.
Your installer should establish the correct connection process before work begins, particularly if the system includes battery storage, multiple inverters or plans for future expansion.
What Is a G98 Application?
A G98 notification is the process used to notify the local Distribution Network Operator (DNO) that an eligible, compliant microgeneration system has been connected to the electricity network.
Unlike the standard G99 process, a qualifying G98 installation can generally be installed and commissioned before the notification is submitted.
The process usually involves:
- Confirming eligibility: Your installer checks the inverter specifications, generating capacity and applicable G98 requirements.
- Installing and commissioning the system: The installation must comply with the relevant technical and safety standards.
- Submitting the notification: The required information is sent to the DNO, normally within 28 days of commissioning.
- Retaining the records: Your installer should keep the relevant submission and commissioning documentation.
A G98 notification is not the same as a G99 approval. The installer must confirm that the installation genuinely qualifies for G98 before using this route.
What Is a G99 Application?
A G99 application requests approval to connect generation equipment that falls outside the G98 process.
The installer normally submits the proposed system details before installation or connection proceeds. Depending on the project, the DNO may assess the equipment specifications, proposed generation capacity, existing network conditions and maximum permitted export.
The DNO may approve the connection as proposed, impose technical or export conditions, request further information or identify network work that needs to be completed.
Allow time for the application and any additional requirements when planning your installation. The timescale depends on the DNO and the complexity of the project.
Why Can’t Every Solar System Use G98?
Many homeowners ask why installers don’t simply register every installation under G98. The answer is grid protection. Electricity networks were originally designed for homes consuming power – not exporting significant amounts into the grid.
Larger systems have a greater impact on local voltage levels and network stability, so the DNO needs to assess whether the infrastructure can support additional exported electricity safely to protect your property, neighbouring homes, local substations and the wider electricity network.
What Does a G98 or G99 Certificate Look Like?
Homeowners often search for a G98 certificate, G99 certificate or DNO approval letter because they want proof that their solar PV system has been correctly connected to the electricity network.
The documentation you receive depends on the connection process and the response issued by your DNO.
G98 notification records
For a G98 installation, relevant records may include the completed notification, confirmation of submission or receipt, commissioning information and the applicable installation documentation.
Because G98 is a notification process, you should not assume that every DNO issues a document formally titled a “G98 certificate”.
G99 approval documents
For a G99 installation, the DNO will normally issue a formal response setting out whether the proposed connection is approved and any conditions that apply.
Depending on the project, the documentation may include:
- The DNO’s connection approval or offer.
- Maximum permitted export capacity.
- Technical requirements or protection settings.
- Conditions that must be met before connection.
- Further commissioning or compliance evidence, where required.
What if I cannot find my DNO paperwork?
Contact the installer who completed the work first. They should be able to explain which connection procedure was used and help locate the relevant notification, approval and commissioning records.
If necessary, the installer can contact the DNO to establish what information is held on its records.
If you are buying a property with existing solar panels, ask the seller for any available DNO documentation alongside the system specifications, electrical certificates and warranty information.
Can Battery Storage Affect G98 or G99?
Yes. Adding battery storage can affect which DNO connection requirements apply, but the battery’s storage capacity in kWh does not, by itself, determine whether an installation falls under G98 or G99.
The installer needs to assess the electrical characteristics of the complete system, including the solar inverter, battery inverter or hybrid inverter, generating capacity, phase configuration and any applicable export limitation arrangements.
For example, a homeowner may have a solar array that appears suitable for a small domestic installation but choose a larger hybrid inverter to accommodate battery storage and future expansion. The complete system may then require a G99 application rather than a G98 notification.
An existing solar installation can also need further assessment when a battery or additional generation equipment is added. The correct process depends on the proposed modification and the existing connection arrangements.
Can an export limit allow a larger system to use G98?
Not automatically. An export limitation system may restrict how much electricity a property sends to the grid, but this does not automatically make equipment eligible for G98.
G100 provides requirements for export limitation schemes. Where an installation needs an export limitation arrangement, the installer must establish which connection standards and DNO approvals apply to the complete design.
Before adding a battery or upgrading an inverter, ask your installer to confirm:
- Which connection procedure applies to the revised system.
- Whether the existing DNO notification or approval remains sufficient.
- Whether a new application or modification request is required.
- Whether the DNO has imposed a maximum export limit.
- Whether any additional technical equipment or commissioning evidence is needed.
Planning the solar and battery system together helps avoid unnecessary redesigns, delays and additional costs.
Does G99 Mean I Need Solar Planning Permission?
No, this is a common misconception. Solar planning permission and G99 approval are completely different. Planning permission relates to whether your local authority allows the physical installation. G99 relates to connecting your system safely to the electricity network.
Most homes benefit from Permitted Development Rights, meaning planning permission isn’t required for roof mounted solar PV systems. However, you may need planning permission if your property is listed, within a conservation area, subject to planning restrictions or installing a large ground mounted system. Your installer should advise on both planning requirements and DNO approval separately.
What Is a DNO Letter?
A DNO letter is simply written confirmation from your Distribution Network Operator. Depending on your project, it may include:
- Confirmation that your G99 application has been approved
- Export limitations
- Network upgrade requirements
- Permission to connect
- Technical conditions
Most homeowners never need to deal with this paperwork themselves because SolarTherm UK manages the entire application process on your behalf.
What Happens if G99 Approval Is Delayed or Refused?
A G99 application does not guarantee that the DNO will approve a proposed solar installation exactly as designed.
The DNO may need additional technical information or may identify constraints on the local electricity network. In some cases, the proposed connection may be approved subject to restrictions or additional work.
If the application is delayed, your installer can check whether further information is required and provide any outstanding documents.
If the DNO cannot approve the original design, possible next steps may include:
- Reviewing the proposed inverter capacity.
- Considering a permitted export limitation arrangement.
- Revising the system design.
- Assessing whether network reinforcement is required.
- Discussing alternative connection arrangements with the DNO.
The available options depend on the reason for the decision and the technical requirements of the network. Export limitation does not guarantee approval, and network reinforcement may involve additional cost or time.
This is why DNO requirements should be considered during system design, rather than left until the installation date has been arranged.
Why Professional DNO Management Matters
Incorrect G98 or G99 applications can delay installations and create unnecessary costs. Choosing an experienced installer means:
- Accurate system design
- Correct inverter sizing
- Proper DNO submissions
- Compliance with current Engineering Recommendations
- A smoother installation process
SolarTherm UK manages every stage – from your initial survey through to final grid notification – so you don’t have to navigate technical regulations yourself.
Why Homeowners Across the South East Choose SolarTherm UK
With over 16 years of experience designing and installing residential solar PV systems, SolarTherm UK understands both the technical requirements and the practical considerations involved in connecting your home to the electricity network.
Our qualified in house engineers work to current industry standards and stay up to date with changes to DNO processes, Engineering Recommendations and UK installation best practices.
Whether you’re installing a modest rooftop system of a larger solar and battery solution, we’ll determine whether your project falls under G98 or G99 and manage the application on your behalf.
Our expertise supports homeowners across Essex, Kent, Suffolk, Hertfordshire and the surrounding South East and East Anglia, helping ensure installations are compliant, efficient, reliable and completed with minimal disruption.
Contact SolarTherm UK today for a free, no obligation quote and design, tailored to your property, usage and future energy needs. No hard sell, just honest, expert advice – and the time you need to make an informed decision.
Your home. Your energy. Your future.
Frequently Asked Questions
G98 is a connect-and-notify process for qualifying microgeneration equipment, whereas G99 generally requires an application and approval before the relevant installation or connection proceeds. The correct route depends on the equipment, generating capacity and applicable technical requirements.
A Distribution Network Operator (DNO) manages the local electricity network and ensures new solar installations can safely connect to the grid.
For G99 installations, yes. Your installer will usually receive the approval documents and manage the process on your behalf before providing confirmation to you.
No. G99 concerns grid connection, whereas solar planning permission relates to local planning rules. Most domestic rooftop solar installations fall under Permitted Development Rights.
Battery storage can affect the connection requirements, particularly when it introduces a larger inverter or additional generation capability. The installer must assess the complete system, including existing equipment, the proposed battery arrangement and export limitations, before deciding which procedure applies.
Your installer will calculate the inverter output and determine which Engineering Recommendation applies before installation begins.
G98 applies to eligible, type-tested microgeneration equipment operating at up to 16 amps per phase on a low-voltage distribution network. For a typical single-phase domestic system, this is approximately 3.68kW of AC output. The installation must meet the applicable technical requirements and be notified to the DNO within the required period, normally 28 days after commissioning.
For an eligible installation, your installer normally completes and submits the required G98 notification after commissioning. G98 is a notification process rather than the same type of advance approval required for a typical G99 connection.
The timescale depends on the DNO, the completeness of the application and the complexity of the proposed connection. Straightforward applications may be processed more quickly than projects requiring network studies, further information or additional works. Ask your installer for a project-specific estimate.
You should not proceed with the relevant installation or grid connection on the assumption that G99 approval will be granted. The required approval should normally be obtained before the applicable work or connection proceeds. Your installer should confirm the permitted sequence for your specific project.
A G98 certificate is a term commonly used when searching for evidence that a solar installation has been notified under G98. The actual documentation may be a notification submission, receipt or associated commissioning record rather than a document formally called a certificate.
A G99 certificate is a term homeowners sometimes use to describe evidence of DNO approval. The formal documentation may instead be an approval letter, connection offer or other DNO correspondence specifying the conditions of the connection.
A DNO may decline a proposed connection in its current form, request further information or require changes to the design or connection arrangements. The appropriate next step depends on the reason for the decision and the DNO’s technical requirements.
An export limit does not automatically mean that G99 is unnecessary. The applicable requirements depend on the generating equipment, the connection arrangements and the export limitation scheme. Your installer should establish the correct DNO process before installation.
The solar installer or an appointed specialist will commonly handle the DNO notification or application on the customer’s behalf. The homeowner should ask who is responsible for the submission and request copies of the relevant records once the process is complete.
