TL;DR
If you are planning solar panels or a battery, the DNO application is not just admin, it is one of the most important parts of the project because it determines what size system you are allowed to install, how much you can export, whether you might face connection costs, and how your payback stacks up. This guide explains what a DNO application is in the UK, what your Distribution Network Operator looks at, and why local grid capacity can feel first come first served, so you can avoid expensive design mistakes later.
What Is a DNO Application?
A DNO application is a formal request to your local Distribution Network Operator UK to connect a solar or battery system that has the potential to export electricity to the grid. They are responsible for keeping local voltages within safe limits and ensuring cables and transformers are not overloaded.
Your Distribution Network Operator is not your electricity supplier.
In England and Wales, your Distribution Network Operator will be one of several regional companies responsible for maintaining the electricity network, including UK Power Networks, Scottish and Southern Electricity Networks, National Grid Electricity Distribution, and Northern Powergrid, depending on where your property is located.
If you install a grid-tied inverter, you must reason with your DNO. If your inverter has the potential to export, a DNO process applies.
It does not matter if:
• You intend to export
• You think you will use all your solar on site
• You are mainly installing a battery
Why Is a DNO Application Required?
When your solar system exports electricity, it pushes power back into the local network.
That changes how the grid behaves.
Specifically:
• Voltage rises
• Transformers experience reverse power flow
• Cables carry additional current
The statutory voltage range in the UK is between 216V and 253V.
If too many properties export at the same time on a sunny day, voltage can exceed safe limits. The DNO therefore models a worst case scenario: your system exporting at full power, at the same time as other nearby systems. If the network cannot cope, they restrict what you are allowed to do. That is why the DNO application UK process exists.
What Does the DNO Actually Look At?
At residential scale, the DNO application is surprisingly simple because the DNO does not care how many solar panels you have, how big your battery is, or what your annual usage looks like. They mainly care about the inverter rating, because the inverter determines the maximum potential export to the grid, and that is what must be declared on your DNO application.
G98 vs G99 Explained
You can install up to 3.68 kW per phase without prior permission. This is known as a G98 install. You must notify the DNO after installation, but you do not need approval first.
Anything larger requires prior approval under G99. This is where the formal DNO application process becomes critical.
As a general rule:
• Single phase 100A supply → often up to around 17 kW total DNO capacity
• Three phase 100A supply → often around 50 kW
Beyond that, the process becomes significantly more complex.
Inverter Capacity vs Export Capacity
This is where many people get confused, because inverter capacity and export capacity are not the same thing. Inverter capacity is the maximum size inverter you are allowed to install, while export capacity is the maximum power you are allowed to send back to the grid. For example, you might be approved for a 12 kW inverter but given a 7 kW export limit, which means your system can generate up to 12 kW but it can only export 7 kW, and this is very common in many parts of the UK.
Why the Grid Is First Come First Served
Think of the local grid like a cake with only so many slices. The first homes to install solar take the bigger slices of export capacity. As more neighbours install solar, there are fewer slices left, so later homes are offered smaller slices, like an export limit, a lower allowed inverter size, or a quote to pay for upgrades.
Eventually:
• Later applicants may receive export limits
• Or reduced inverter allowances
• Or connection upgrade quotes
This is why the grid is effectively first come first served.
DNO Lead Times
DNOs are permitted to take up to 11 weeks to respond to a DNO application, although in quieter periods the turnaround is often closer to six weeks. If an installer promises installation within a month but has not yet submitted the DNO application, that should raise concerns. There is no such thing as a special relationship with a Distribution Network Operator, and larger systems should always receive formal approval before installation begins. In some cases, the DNO may apply connection charges, and if equipment has already been installed before approval, your options can be very limited.
Can You Reapply Later?
Yes, you can reapply for more capacity later, and it is often worth considering because the UK grid is constantly being upgraded through things like substation refurbishments, cable replacements, and capacity increases. If you were restricted several years ago, a new application may result in a better outcome, and the DNO cannot take away capacity that has already been granted and installed. The worst case is they confirm your original limit, and the best case is they approve a higher allocation.
Spirit Energy DNO Application Service
We now offer a standalone DNO application service starting at £120 + VAT.
This includes:
• Preparing and submitting your application
• Managing all DNO correspondence
• Interpreting the results
• Explaining what they mean for system design
If you would like us to handle a DNO application for you, or if you want to understand what your local grid can support, get in touch with Spirit Energy and we will guide you through it properly. This is available whether or not you proceed with installation with us.
