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If you are considering solar panels, home battery storage, or other electrical equipment for your home, you may have heard your installer mention a DNO application. It is an important part of the process, but it is something most homeowners have never come across before.
DNO stands for Distribution Network Operator. Your DNO is the company responsible for operating and maintaining the local electricity network that supplies your property. When you install a new a solar PV system, battery storage, or certain other electrical equipment, your installation may need to be notified to or approved by the DNO before it can be connected to the electricity network.
So, what exactly is a DNO application, why is it needed, and what does it mean for your solar installation?
DNO stands for Distribution Network Operator. Your DNO is responsible for the electricity distribution network in your area, including the local cables, substations, and other infrastructure that can carry electricity from the wider network to your home or business.
The DNO is different from your electricity supplier. Your supplier is the company you pay for your electricity, such as Octopus Energy or British Gas. The DNO operates the physical electricity network that delivers electricity to your property. There are several DNOs operating across Great Britain, so the company responsible for your property depends on where you live.
A DNO application is part of the process of connecting a solar PV system or battery storage system to the electricity network. Solar panels generate electricity, and a battery can discharge electricity back towards your property’s electrical system. If your system is capable of exporting electricity to the grid, the DNO needs to know about it.
This is because the local electricity network has been designed around particular levels of electricity generation and demand. The DNO needs to make sure that a proposed installation can be connected safely, without causing problems for the local network. It does not necessarily mean that the electricity network needs to be upgraded; in many cases, the proposed installation can be connected without any major changes.
Not every solar installation requires the same type of DNO application. The requirements depend on the size and specification of the system, particularly its maximum export capacity. Your installer should establish what notification or application is required as part of their design and installation process.
Smaller systems may qualify for the simpler notification process, while larger systems may require an application and approval from the DNO before installation can proceed.
G98 is a simplified notification process for certain smaller electricity generating installations. If a solar PV system has an export capacity of 3.68kW or less, the installer can generally install the system and then notify the DNO rather than waiting for formal approval before carrying out the installation.
There are limitations as to what can be connected under G98, and the equipment must be certified accordingly. Your installer should confirm which process applies to your installation, rather than assuming that every solar system can use G98.
G99 is the process used for larger or more complex generation installations that do not fall within the simpler G98 requirements. A larger solar PV system or battery installation may require a G99 application to be submitted to the DNO. Depending on the proposed system and your local electricity network, the DNO may approve the connection as proposed, place conditions on the connection, or require changes before it can be connected.
The time required depends on the type of application, the DNO, and the complexity of the proposed installation.
A G98 notification is done after the installation is complete, so there is no time limit. A G99 application can take over a month; every DNO has a different timescale.
We deal with the relevant DNO process as part of your solar and battery installation. This means you do not need to work out which application you need, or contact the DNO yourself. It is still worth allowing some time for the process when planning your installation, particularly if you are installing a larger system or one with a higher export capacity.
A DNO application being rejected does not mean that you cannot have solar panels or battery storage. The DNO may determine that the proposed system cannot be connected in its original form due to limitations on the local electricity network. For example, there may be restrictions on how much electricity your installation is allowed to export to the grid.
In some cases, the system can be redesigned to meet the DNO’s requirements. This could involve reducing the permitted export capacity, or making other changes to the proposed installation. Your installer should explain what the DNO have requested and what your options are.
It is easy to assume that the DNO only needs to know about your solar panels, but battery storage is also relevant. A home battery can store electricity from your solar panels and then provide that electricity to your home later. Depending on how the system is configured, it can also import electricity from the grid and discharge electricity back towards the grid.
This means the battery’s inverter and export capability need to be considered when assessing the connection. A battery can therefore require DNO notification or approval, even if you are not installing solar panels.
No, not necessarily. The answer depends on the type of connection being proposed and the DNO process that applies. For some smaller installations, the notification process can be completed after installation. Other systems need DNO approval before the installation can proceed. This is something your installer should establish during the design stage; it is one of the reasons a proper technical survey and system design are important before installation day.
Your installer will need to send the DNO a application form, schematic of the proposed installation, and a letter of authority from you which gives them permission to apply on your behalf.
The application form will include details on the inverter and battery storage, maximum export capacity, and information on your existing electrical supply. This is usually all handled by your installer, so you should not need to understand all of the technical information yourself.
A DNO approval is confirmation from the Distribution Network Operator that a proposed electrical generation or storage system can be connected to the network, subject to any conditions they specify. For example, the DNO may approve a system with a particular maximum export limit.
This is separate from MCS certification. MCS relates to the certification of the installer and installation standards, while the DNO process relates to connecting the system to the electricity distribution network. Both form important parts of a properly completed solar installation.
You may come across solar and battery installers who tell you that your system does not need a G99 application because it can be installed under G98. There is some important context behind this.
G98 allows certain generating equipment to be connected to the electricity network without going through the same pre-installation approval process as a G99 application. The G98 limit for a single phase connection is 3.68kW, equivalent to 16 amps at 230 volts. However, the size of the equipment you see on a quotation is not necessarily the same as the amount of electricity that will be exported to the grid.
As an example, a battery or inverter with a higher potential output can often be configured so that its export to the grid is restricted to 3.68kW. Export limitation is a recognised part of the DNO framework, and G99 documentation specifically allows for installations using export limitation schemes.
This is why you may see relatively large solar or battery systems being installed under a G98 arrangement by some installers.
We take a more straightforward approach when designing solar and battery systems. If the inverter being installed is capable of exporting more than 3.68kW on a single phase connection, we will apply for G99 rather than simply limiting the system and installing it under G98.
There are equipment manufacturers that have certified their products for G98 operation when appropriately configured and export limited. A good example is Tesla Powerwall 3, which is available in configurations ranging from 3.68kW through to 11.04kW of nominal AC output. A Powerwall 3 can therefore be configured with a lower permitted grid export, while the underlying equipment is capable of considerably more. This can be a perfectly legitimate way of designing a system where the customer’s requirements do not justify a higher export connection.
Where the inverter is capable of exporting more than 3.68kW, we prefer to apply for the appropriate G99 approval rather than automatically restricting the system simply to avoid the G99 process.
There are legitimate reasons for limiting export. The local electricity network may not be able to accept the full potential export from a proposed installation, or the customer may not want a high export capacity. Export limitation can be a useful tool when designing a solar or battery system.
The important thing is to understand what you are actually getting. A battery may have a large storage capacity, but its export to the grid could still be restricted. Similarly, an inverter may be technically capable of producing more power than the amount it is permitted to export to the network. The export limit and the battery’s ability to supply your home are not necessarily the same thing.
Our approach is designed to give our customers the greatest flexibility from the system they have paid for. If we are installing an inverter that is capable of exporting more than 3.68kW, we will apply for G99 so that the system can be connected with the appropriate approved export capacity, subject to the DNO’s assessment and approval. We don’t restrict the system just for the sake of avoiding a G99 application.
This also gives us the opportunity to establish what the local network will actually allow. The DNO may approve the proposed export capacity, impose an alternative limit, or request changes to the proposed connection. We would rather establish this properly as part of the design and connection process.
It realty depends on the proposed solar system. G98 is a perfectly valid connection route when the installation meets the relevant requirements. A properly designed G98 system can work extremely well. G98 and G99 are not simply different quality levels.
G98 and G99 are different connection processes, and which one is appropriate depends on the generating equipment, its certified configuration, the aggregate capacity, and the proposed export arrangement.
Our policy is simply that, where the inverter is capable of exporting more than 3.68kW, we will apply for G99 rather than automatically limiting your system to G98 level.
Yes. Where a G99 application is required, the cost of the application and the associated administration is included within our quotation. This is something worth checking when comparing solar and battery quotations. Not every installer takes the same approach to DNO applications, and a quotation that appears cheaper at first may not necessarily include every part of the connection and certification process.
We prefer to be clear about what is included from the beginning, so there should not be an unexpected additional charge simply because a G99 application is required.
If you are comparing solar or battery quotations, it is worth asking the installer exactly how they intend to connect the proposed system to the electricity network. Ask whether your system will be connected under G98 or G99, and whether your inverter is being deliberately export limited. You should also ask whether the DNO application or notification is included within the quoted price.
Two systems can look very similar on a quotation, but have quite different connection arrangements. The important thing is not simply whether an installer says your system can be installed under G98. You should understand why it qualifies for G98, whether the equipment is being export limited, and whether that limitation affects what you want the system to do.
We will always explain the proposed connection arrangement as part of the system design and deal with the relevant DNO process for you.
Once your solar PV or home battery system has been installed, there may be further notification or certification requirements. Your installer will complete the relevant paperwork and provide you with the documentation relating to your installation. For MCS certified installations, the MCS certificate is important for accessing the Smart Export Guarantee (SEG). Your installer can explain what paperwork you will receive once your installation has been completed.
Yes, when we design and install a solar PV or home battery storage system, we deal with the relevant DNO process as part of the installation. We assess the proposed system and establish which process is required based on the equipment being installed and its electrical characteristics.
Wherever a formal DNO application is required, we will submit all required documentation and manage the process on your behalf. This means you can concentrate on choosing the right system for your home, rather than trying to navigate the technical requirements of the electricity network yourself.
The DNO process is there to ensure that any new electricity generating and storage systems can be safely connected to the local network. If you are comparing solar quotes, it’s definitely worth asking whether the quotation includes the relevant DNO application or notification, and whether the installer will deal with the process on your behalf.
A good solar installation is about more than just putting panels on the roof. The system should be correctly designed, connected, certified, and commissioned so that everything works together properly and safely.
If you are considering solar panels, a home battery, or both, HeatElectric can design a system around your property, electricity usage, and requirements. We can explain the full DNO process, deal with any relevant applications, and guide you through the installation from initial survey through to commissioning and certification. The right system isn’t necessarily the biggest system you can fit on your roof; it is about choosing the right combination of solar generation, battery storage, and electrical equipment for the way you use energy in your home.
