DNO Approval Explained for Home Solar Panels
DNO stands for Distribution Network Operator. A DNO is the company responsible for operating and maintaining the local electricity distribution network that supplies homes and businesses across the UK.
When installing solar panels, your DNO is responsible for assessing or registering the connection to the electricity network, depending on your system’s size and technical requirements. Some installations require approval before connection, while others can be registered after installation.
At SolarTherm UK, we manage the entire DNO application process on behalf of our customers across Essex, Kent, Suffolk, Hertfordshire and the wider South East and East Anglia, making the journey from quotation to installation as smooth as possible.
What Does DNO Mean?
One of the most common questions homeowners ask is:
“What is the meaning of DNO?”
A Distribution Network Operator (DNO) is the company responsible for maintaining and operating the electricity distribution network in your local area. They own the cables, substations and infrastructure that deliver electricity to homes and businesses.
Your electricity supplier sells your energy, while your DNO ensures the local electricity network remains safe and reliable. When you install solar panels, your system can export surplus electricity to the grid. The DNO needs to ensure that your local network can safely accept this additional generation without affecting neighbouring properties.
Why Does Solar Need DNO Approval?
Solar PV systems don’t simply generate electricity for your home. When your panels produce more electricity than you’re using, the surplus energy is exported to the National Grid. If many homes export large amounts of electricity at the same time, local electricity networks can become overloaded.
The DNO approval process helps to:
- Protect the local electricity network
- Prevent voltage fluctuations
- Maintain grid stability
- Ensure electrical safety
- Support future renewable energy growth
For most homeowners, this process is handled entirely by their installer. At SolarTherm UK, we submit all necessary applications, communicate with the DNO and ensure your installation complies with current engineering recommendations.
What Is a DNO Letter?
You may hear installers mention a DNO letter during the quotation process. A DNO letter is simply written confirmation from your Distribution Network Operator regarding your solar installation.
Depending on the project, this could include:
- Confirmation that your installation has been registered
- Approval for connection
- Permission to export above standard limits
- Confirmation of any export restrictions
- Technical requirements before installation
Most homeowners never need to deal directly with the DNO because their installer manages the process from start to finish.
How do I get a DNO letter for solar panels?
If you’re installing solar panels in the UK, your installer will normally manage the DNO process on your behalf.
For systems requiring prior approval under G99, the installer submits an application to the relevant Distribution Network Operator. Once assessed, the DNO may issue a connection offer or written approval setting out the conditions for connecting your system.
For installations qualifying under G98, the installer generally notifies the DNO after commissioning, and the DNO may provide a registration acknowledgement.
Your DNO correspondence may include:
- The property address and connection details
- An application or registration reference number
- The approved generating capacity
- Any export limitations or connection conditions
- Confirmation of approval or registration
If you need a copy of your DNO documentation, contact your original solar installer first. They should be able to provide the relevant correspondence or advise you how to obtain it.
Do All Solar Panels Need DNO Approval?
All grid-connected solar PV installations must follow the relevant DNO connection requirements, but not every system needs approval before installation.
Smaller installations that meet G98 requirements can generally be connected and then registered with the DNO within the required notification period.
Larger systems, or installations that do not qualify for G98, will generally require an application under G99 and written permission before connection.
The correct process depends on the inverter and generating capacity, the electrical supply, any existing generation or battery storage, and the applicable connection rules.
At SolarTherm UK, we assess these requirements during the system design process and manage the relevant DNO paperwork on behalf of our customers.
Understanding G98
G98 is the simplest connection process for domestic solar installations. It applies to smaller generating systems that fall within specific export limits. Rather than asking for permission before installation, qualifying G98 systems are generally installed first and then registered with the DNO afterwards.
Typical characteristics include:
- Smaller residential systems
- Straightforward notification process
- Faster approvals
- Lower administrative requirements
Many standard domestic solar installations fall under G98, although battery storage and larger inverter sizes can change which application is required.
Understanding G99
G99 applies to larger or more complex solar installations. Unlike G98, approval must usually be obtained before installation begins. A G99 application allows the DNO to assess whether the local electricity network can safely accommodate the proposed generation capacity.
This process may include:
- Network studies
- Export assessments
- Connection conditions
- Export limitations where necessary
Although the application process can take longer than G98, it allows homeowners to install larger systems that may better meet their long term energy requirements.
What Is G100?
G100 is often misunderstood but can be extremely useful. Rather than reducing the size of your solar installation, G100 allows an installer to electronically limit how much electricity is exported to the grid. This means you may be able to install a larger solar array while ensuring exports stay within the level approved by the DNO. A G100 compliant export limitation system continuously monitors electricity flowing to the grid and automatically reduces exports whenever necessary.
This allows homeowners to:
- Install more solar panels
- Generate more electricity for their own use
- Charge larger battery storage systems
- Future proof their property
- Remain compliant with DNO requirements
What Are Export Limitations?
An export limitation controls the maximum amount of electricity your property can send back to the grid. Rather than limiting how much electricity your solar panels produce, it only limits exported energy. Any electricity used within your home isn’t affected.
For example, if your home is using 5kW while your panels produce 8kW, only 3kW is exported. If your DNO export limit is 3kW, the system operates normally. If exports would exceed that level, the export limitation system automatically adjusts inverter output.
For many homeowners, export limitation offers the best balance between maximising self-consumption and complying with grid requirements.
Understanding Inverter Capacity Limits
One area that often causes confusion is inverter sizing. Your solar panels and inverter are closely linked, but they perform different jobs. Solar panels generate DC (direct current) electricity and the inverter converts it into usable AC (alternating current) electricity for your home.
The size of your inverter plays a major role in determining whether your installation falls under G98 or G99 requirements. Larger inverter capacities generally require additional DNO assessment because they can potentially export more electricity onto the network.
An experienced installer will design your system to achieve the best balance between:
- Roof size
- Household electricity demand
- Battery storage
- Future EV charging
- Heat pump compatibility
- DNO requirements
At SolarTherm UK, every system is individually designed rather than relying on standard package sizes.
Can Battery Storage Affect DNO Approval?
Yes. Battery storage systems can influence which application is required, particularly where batteries can export electricity back to the grid. Hybrid inverters, AC coupled batteries and larger battery systems may all affect the overall export capability of the installation.
This is why a professional system design is essential before installation begins. Our technical team assesses the complete system – including solar panels, inverter and battery storage – to ensure full compliance before any work starts.
Do I Need to Apply to the DNO Myself?
In almost every residential installation, the answer is no. A reputable MCS certified installer should:
- Design your system correctly
- Identify the correct application type
- Complete all paperwork
- Submit applications
- Liaise with the DNO
- Obtain approvals where required
- Provide confirmation once complete
This removes the complexity for homeowners and ensures everything complies with UK regulations.
Why Professional System Design Matters
Choosing the right installer is about much more than fitting solar panels. Incorrect inverter sizing, overlooked export limits or incomplete can delay installations or require expensive modifications later.
At SolarTherm UK, every project includes:
- Detailed site survey
- Bespoke system design
- DNO assessment where required
- MCS compliant installation
- NICEIC certified electrical work
- Full commissioning and testing
- Ongoing customer support
Our experienced team has delivered residential solar installations across Essex, Kent, Suffolk, Hertfordshire and the wider South East and East Anglia, helping homeowners navigate planning requirements, DNO approvals and electrical regulations with confidence.
Whether you’re installing a small rooftop system or a larger battery backed solution, we’ll ensure your project is designed for maximum performance while remaining fully compliant.
Why Choose SolarTherm UK?
When investing in solar, experience matters. SolarTherm UK combines technical expertise with a customer first approach, ensuring every installation is designed around your home’s energy needs and future plans.
As an MCS certified contractor, NICEIC approved installation and EPVS Gold Standard member, we work to recognised industry standards and stay up to date with the latest engineering recommendations and regulatory requirements. Our in house teams manage everything from initial design through to DNO applications, commissioning and aftercare, giving homeowners complete peace of mind.
Whether you’re installing solar panels for the first time or expanding an existing system with battery storage, we provide honest advice, transparent quotations and fully compliant installations throughout Essex, Kent, Suffolk, Hertfordshire and the surrounding South East and East Anglia.
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
DNO stands for Distribution Network Operator. They manage the local electricity network and determine how solar systems connect and export electricity safely.
A DNO letter is written confirmation regarding your solar connection, such as approval, registration or export conditions for your installation.
G98 generally applies to smaller domestic systems that can be notified after installation, while G99 usually requires approval before installation for larger or more complex systems.
G100 is an export limitation standard that allows larger solar systems by controlling how much electricity is exported to the grid.
Not necessarily. Export limitations only affect electricity sent to the grid. Electricity used within your home or stored in a battery can still help reduce your energy bills.
No. Solar planning permission and DNO approval are separate requirements. Most residential solar panel installations fall under permitted development, while DNO approval relates to connecting your system safely to the electricity network. Certain properties, such as listed buildings or homes in conservation areas, may still require planning consent.
DNO approval times vary depending on the Distribution Network Operator, the size of your solar PV system and whether the local electricity network has sufficient capacity. Straightforward applications may be processed relatively quickly, while more complex installations can take considerably longer.
Applications requiring a detailed technical assessment or network reinforcement may experience additional delays. Your solar installer should explain the expected timescale and keep you informed of any updates from the DNO.
A DNO approval letter is a document issued by your Distribution Network Operator confirming the outcome of a connection application. Depending on the application, it may include your property address, application reference, approved generating capacity, connection requirements and any restrictions on exporting electricity to the grid.
The format varies between network operators. Some installations receive a formal connection offer, while others receive an approval or registration acknowledgement. Your installer should be able to provide the relevant documentation for your system.
You must follow the applicable DNO connection requirements before connecting a grid-connected solar PV system. However, not every installation requires prior approval.
Systems that meet the requirements of Engineering Recommendation G98 can generally be connected before the DNO is notified within the required timeframe. Larger or more complex systems may require a G99 application and permission before connection. Your installer should establish which process applies to your installation.
Your Distribution Network Operator is determined by the area where your property is located, rather than your electricity supplier. You can identify your network operator using the electricity network operator lookup service or by checking your electricity bill for relevant network information.
Once you know your DNO, you can use its website to find information about connection applications, solar PV requirements and electricity export limitations.
Adding a battery to an existing solar PV system may require a new DNO application or notification, depending on the battery inverter, the existing installation and the proposed operating configuration.
A battery can change the system’s ability to export electricity to the grid, even if the solar panels themselves remain unchanged. Your installer should assess the combined generating and storage arrangement, check any existing export restrictions and determine whether G98, G99 or G100 requirements apply.
If your solar PV or battery system is subject to an export limit, the installation must be configured to comply with the relevant connection conditions. Exceeding that limit could breach the agreed connection requirements and create issues for the local electricity network.
An export limitation scheme, where appropriate, can restrict how much electricity the system sends to the grid. Your installer should confirm that any required export-limiting equipment is correctly specified, configured and commissioned.
A DNO can refuse a proposed connection in its current form if technical constraints, network capacity or other connection requirements cannot be satisfied. In some cases, the operator may offer an alternative connection arrangement, impose export restrictions or require network reinforcement.
A refusal does not necessarily mean solar panels are impossible to install. Your installer may be able to review the system design, consider a suitable export limit or discuss the available options with the DNO.
You may need a further DNO application or notification if you change your existing solar PV system, add battery storage, increase generating capacity or alter equipment in a way that affects the grid connection.
Whether a new application is required depends on the existing approval, the proposed changes and the applicable engineering requirements. Before making changes, ask your installer to check your existing DNO documentation and confirm the correct process.
No. DNO connection approval and MCS certification serve different purposes.
DNO procedures concern connecting your solar PV or battery system to the electricity distribution network and complying with the relevant technical requirements. MCS certification relates to eligible renewable energy installations and the certification of installers and products under the applicable scheme requirements.
Depending on your installation and circumstances, you may need to consider both. DNO approval does not automatically mean an installation is MCS certified, and MCS certification does not replace the applicable DNO connection process.
