DNO Solar Application UK: Grid Approval for Rooftop Solar Systems
- Planning a Rooftop Solar System Before the DNO Application Stage
- DNO Application Routes for Different Rooftop Solar Installations
- Technical Information Needed for a Solar DNO Application Review
- DNO Assessment, Export Limits and Solar Connection Conditions
- Solar Battery Storage After DNO Connection Planning Is Complete
- Solar Application Decisions to Confirm Before Installation Begins
- Conclusion
- FAQs
Rooftop solar isn't just about the panels and how much electricity they can produce. If the system is intended to be connected to the public electricity network, then the proposed design may also be required to go through the appropriate DNO solar application or notification process.
The path will depend on the size and layout of the installation. Smaller eligible systems may be G98, and larger capacity systems or more complex projects may need to be G99 and assessed by the DNO prior to connection. Inverter output, existing generation, battery storage and expected export are all factors that can influence that decision.
These details are particularly critical for conventional rooftop PV where the opportunity exists to influence the final PV system design upon network approval. This guide outlines how to plan for a solar DNO application, the technical information likely to be required, how export limits can impact a project, and the role of battery storage once the grid-connection plan is established.
Planning a Rooftop Solar System Before the DNO Application Stage
The process for a successful DNO solar application begins soon after you submit the forms. The proposed panel array, inverter, expected home use and any battery storage should be thought of as one unit. Knowing these basics early helps the installer create a clearer technical design and reduces the risk of later equipment changes if the proposed grid connection proves unsuitable.
Solar Generation, Household Use and Export Across Grid Connections
Rooftop solar first supplies electricity to appliances operating within the home. If the electricity is not needed immediately, it can be exported via the grid connection when generation exceeds immediate demand.
This is important for planning household consumption early on. One house might consume a higher percentage of its production and another might have a larger surplus on a more frequent basis.
While self-consumption affects solar economics, the DNO's main concern is how the proposed generation impacts the local network. The probable export configuration should be included in the anticipated solar production, not as an afterthought once the installation has been designed.
Rooftop PV System Size and Inverter Capacity Before Application
Panel capacity shows how much electricity a rooftop PV system can generate, while inverter capacity is more important for rooftop grid-connection planning, as the inverter regulates the AC output into the home's electrical system.
A bigger panel array doesn't necessarily mean the same export at any given time. Actual power flows are dependent on panel orientation, weather, household demand and inverter configuration.
To ensure the proposed array size and inverter rating are suitable, and that the installer doesn't overlook any existing generation at the property, they should confirm the proposed array size and inverter rating before submitting the application. These details help determine whether the installation is on a G98 route or a G99 installation.
Battery Storage as Part of the Proposed Solar Connection Design
Battery storage can change how solar electricity moves on the premises. Surplus generation can be stored for later in the day; not all surplus generation is exported immediately.
But a battery is more than a simple energy-saving device. Its inverter and operating configuration may also have significance for the solar grid connection assessment, especially if solar and storage are to be installed together.
Including battery storage in the original design gives the DNO and installer a more accurate picture of the proposed system. After the full configuration is made, the next step is to select the right G98 / G99 application route.
DNO Application Routes for Different Rooftop Solar Installations
Once the proposed rooftop system is clear, the installer can decide which grid-connection route is suitable. This is largely determined by the capacity of the inverter, the amount of generation already connected on site and whether the DNO requires an assessment of the network prior to the new system being turned on. It is also important for the homeowner to understand this at the outset, to avoid designing a system based on assumptions that may ultimately be incorrect.
G98 Routes for Eligible Smaller Rooftop Solar PV Installations
G98 is a much easier process for small scale generation that is eligible for connection to the low voltage network. Where it can be installed, it is typically a connect-and-notify installation, rather than waiting for full pre-connection approval, which applies when the installation reaches the relevant technical and capacity limits.
This is suitable for many smaller domestic rooftop systems, subject to confirmation from the full installation. The assessment may be impacted by existing solar generation or other inverter-based equipment at the property.
The installer must also use compliant equipment and provide the DNO with the required data after commissioning. First, homeowners who want a clearer idea of the physical setup should be able to understand how solar panels connect to the home's electricity before reviewing the network paperwork.
G99 Applications for Higher-Capacity or Complex Solar Systems
A G99 application is normally required when the proposed installation is outside the applicable G98 limits, or when the grid connection is more complicated. In a connect and notify route, the DNO generally must evaluate the proposal before connecting the system.
This allows the network operator to assess whether local cables, transformers, and other equipment can withstand the proposed generation. Depending on the project, the DNO will accept the design as submitted, request more technical information, or place conditions on the connection.
Homeowners should therefore allow time for DNO review, rather than treating network approval as a final administrative task, when planning larger rooftop installations.
Export Capacity and Inverter Configuration Affecting the DNO Route
The application route is not dependent on the size of the solar array. The DNO also considers the inverter configuration and how much power the installation might export to the network.
For instance, a system can have high solar generation and an export limitation scheme to reduce the amount exported from the property. Battery storage can further change how generation and export interact.
The information should be accurate and should be captured in the DNO Solar Application. After selecting the right route, the next step is to compile the technical and property information the network operator needs to assess the proposal.
Technical Information Needed for a Solar DNO Application Review
If the technical information in the solar DNO application matches the system to be installed, it's easier to assess. It's not just the number of panels the network operator is interested in - they must also have sufficient information to understand the equipment, connection points and possible power flows. Creating these documents in advance can help to minimize requests for clarification down the road.
Proposed Generation Capacity and Inverter Details for DNO Review
The proposed solar generation size and inverter configuration to interface with the house electrical supply should be clearly stated in the Application.
This is especially important for the inverter, which plays a crucial role in converting the DC power generated by the solar panels into AC power suitable for the building's appliances and for connecting to the electrical grid. Depending on the technicality of the documents, homeowners unfamiliar with this component can first understand the role of a solar inverter.
If more than one inverter/generating unit is used, the application should show the entire setup, not just the newest equipment.
Property, MPAN and Installer Information Used in Solar Applications
The DNO must also determine the appropriate property and electricity connection. This is typically the site address and MPAN (electricity supply point).
The submission may also include information from the installer/company, if technical declarations and/or commissioning responsibilities are applicable. Accurate property information is important as any wrong MPAN or wrong address could be associated with the application with the wrong network connection.
If the property has existing solar generation or battery storage, then this should also be declared so that the DNO can consider the proposed change of context.
Equipment Data and Connection Documents Supporting Submission
Supporting documentation should include inverter specifications, equipment certificates, single-line diagrams, and any other technical information pertinent to the proposed installation.
This varies by connection path and system complexity. Typically a simple domestic installation of G98 would need less detail for pre-connections than would a larger G99 project.
The key is consistency: the equipment listed in the DNO solar application should match what you're installing. With the technical submission complete, the DNO can switch from document review to network assessment and determine if export limits or other connection conditions are required.
DNO Assessment, Export Limits and Solar Connection Conditions
Technical information is not the only thing to be submitted. In systems requiring a pre-connection review, the DNO will also need to determine if the local network has the capacity to accept the generation safely. This evaluation can impact the amount of export power the system can be connected to – and if there are any other requirements that must be met prior to being commissioned.
Network Capacity Checks During the Solar Application Review Process
All local cables, substations, voltage levels and existing generation connected in the area may be considered for review by the DNO. The goal is to see if the proposed rooftop PV system could cause problems like voltage rises or reverse power flow.
That is why two similar solar systems at different sites can produce different results. One network may have plenty of idle bandwidth and can accommodate the proposed design with little change, while another part of the network may need a more tightly managed connection.
During planning, estimated generation is also a factor. According to a solar panel output calculation, the homeowner can gauge expected production, but the DNO's decision will still rely on the technical design of the connection to the solar panels.
Export Limitation Requirements for Some Rooftop Solar Connections
If the network cannot receive the full potential export then the DNO may permit the installation subject to an export limitation scheme.
This enables the domestic consumer to produce and consume more solar electricity locally and limits the amount of electricity fed back into the local grid. The limit shall be determined by appropriate equipment and shall be included as part of the approved system design.
In this scenario, battery storage can be beneficial as some excess generation may be stored rather than exported. The battery and control equipment, however, must still be specified correctly in the connection proposal.
Connection Approval and Conditions Before the Solar System Goes Live
If installing a G99 installation, homeowners should ensure that the G99 is not connected and commissioned until the appropriate DNO approval is obtained. Approval could be for the proposed design as submitted or with conditions, with respect to export, equipment or network operation.
The following conditions are to be discussed with the installer prior to completion of the work. If any changes were to be made after approval (such as increase inverter capacity or change export settings) this could require further DNO review.
With the connection conditions now clear, the next big question for the household is how to match battery storage with solar generation, export behaviour, and daily electricity use.
Solar Battery Storage After DNO Connection Planning Is Complete
However, when the proposed solar connection and any DNO conditions are made clear to the home owner, he or she can make a more informed choice about storage. Battery planning should be based on the approved system design, not an add-on. The goal is to maintain surplus generation (which can be useful for future storage), while ensuring inverter sizing and export conditions align with the connection design and demand doesn't mismatch the home.
EcoFlow STREAM 5000 for New Solar and Storage Home Installations
Households installing rooftop PV and battery storage simultaneously can use the EcoFlow STREAM 5000, which has 5.24kWh of storage capacity and will accommodate up to 4,000W of PV input. This is ideal for homes that want to integrate solar generation and storage from the start.
It stores excess daytime generation rather than exporting it, for use in the evening or night. This can increase self-consumption of solar power and reduce electricity imports during periods of lower solar generation.
EcoFlow STREAM AC 5000 for Existing Solar Homes Adding Storage
The EcoFlow STREAM AC 5000 is designed for a different scenario: households with existing solar panels that want to add solar storage later. The 5.24kWh capacity lets you store excess energy from your current PV system for later use instead of exporting it immediately.
This retrofit option is feasible when the solar system is still appropriate, but the home's energy use has shifted. Adding battery equipment may change the existing technical configuration recorded for the property; however, the installer should check whether the DNO approval/notification needs to be updated.
Matching Battery Storage With Solar Export and Household Demand
Bigger does not necessarily mean better when it comes to batteries. Storage should mirror the amount of excess solar generation that is routinely available, the timing of household electricity consumption and any export constraints that may be associated with the solar PV system connection.
If you use more storage than solar generation most of the time, you might store more energy than you need; conversely, a home that exports several kilowatt-hours most afternoons might benefit from more storage. Knowing the battery storage capacity helps homeowners compare usable storage with what they use in the evening.
After the solar, inverter and battery design, the final step is to make some key application decisions before installation work can commence.
Solar Application Decisions to Confirm Before Installation Begins
The proposed system should match the information provided for the DNO solar application before installation begins. This avoids last-minute design changes and ensures all parties work from the same technical plan, with a short final review.
Confirm Proposed Solar Capacity and Total Inverter Output
Review the final panel size and inverter size in the submitted design. If the property already has generation or storage, consider the overall configuration rather than only the rooftop PV system.
Identify the Appropriate G98 or G99 Connection Route
Determine if the installation is eligible for G98 or requires a G99 application. Make this decision based on the final system design, inverter size, and existing equipment, rather than the number of solar panels being installed.
Prepare MPAN, Equipment and Installation Information Early
Before submission, have the property MPAN, inverter model, equipment specifications, and installer details ready. Good documentation minimises the risk of delays due to incorrect information or discrepancies between the application and the equipment installed.
Check Whether Export Restrictions or Conditions May Apply
Certain connections may receive an export limit and/or other conditions. Before deciding on the final system size, homeowners need to understand the implications of these restrictions, especially when battery storage or export payments are involved.
Receive Required DNO Approval Before Connecting the System
If installation is to grid connection, installation should not proceed until the relevant DNO pre-approval (G99) is obtained. Check the conditions of such approval with the installer and incorporate them into commissioning.
Establishing these points before work provides a stronger technical foundation for the project and reduces the risk of revisiting the application after equipment is installed.
Conclusion
A good DNO solar application ensures a rooftop PV system is designed with the homeowner's energy requirements and the size and strength of the electricity grid in mind. Before the application, it will be helpful to confirm the size of the system, the output of the inverter, current generation and planned battery storage.
For smaller installations that are within the scope of eligibility, the G98 process may be followed; for larger and/or more complex installations, G99 approval may be required prior to connection. Final design may be affected by network capacity and potential export limits.
With these requirements well understood, homeowners can make informed choices about solar generation, battery storage, and self-consumption. Keeping the approved connection information in sync with the equipment actually installed also supports future system upgrades.
FAQs
Can a DNO Ask for Changes to a Proposed Solar PV System Design?
Yes, as part of a DNO solar application, the network operator may determine capacity or voltage limitations that impact the proposed solar connection. It may request changes such as a lower export limit, a different inverter setup, or new control gear. The installer should carefully check any conditions before committing to the rooftop PV design to ensure the installed PV system matches the approved connection.
Does Increasing Solar Capacity Require a Fresh DNO Application?
Yes, adding more panels can increase generation capacity if the inverter is upgraded or new inverter equipment is installed. Even if the original system is already registered, the installer should verify the changes against the latest G98 or G99 requirements. The installer can determine whether an updated notification or a new application is required.
Can Export Limitation Equipment Help With DNO Solar Approval?
Yes, if the local network cannot accept the system's full export potential, an approved export limitation device may allow a larger solar installation to operate without limitations on the amount exported to the network. The proposed export limit and control system should be part of the design approved by the DNO.
Does Adding Battery Storage Change an Approved Grid Connection?
Using battery storage can add another inverter and change the direction of electricity flow between the property and the grid. Check storage against the existing solar system connection arrangement, even if the solar system is already approved. The installer can determine whether the DNO requires an updated technical information submission.
Can a Solar Installation Proceed While a G99 Application Is Pending?
Sometimes the physical installation work may be planned or done while an application is under consideration, but a system that requires G99 approval should not be connected and operated in parallel to the grid without the appropriate approval in hand. Delaying the final connection to wait for the DNO decision also prevents the expense of changing the design if the proposed and approved designs differ.