If you have started researching solar panels for your home, you may have come across something called a ‘DNO application.’ It’s a term that often appears in installation quotes or initial surveys and can seem technical and unfamiliar if you have not encountered it before.

In the UK, every property is connected to a Distribution Network Operator (DNO). These organisations manage the local electricity infrastructure — the cables, transformers and substations between the national grid and individual properties. When solar panels are installed, they generate electricity for the property during daylight hours. Sometimes that production is higher than what the household is using, and the surplus is exported back into the grid. This affects the local network — and that is why the DNO needs to be informed.

For most homeowners, this process happens quietly in the background. Installers usually handle the technical details, submit the required paperwork and liaise with the DNO directly. Understanding what is involved, however, helps you ask the right questions before signing off on an installation.

A Distribution Network Operator (DNO) is the organisation responsible for managing the electricity network in your local area. They maintain the infrastructure that physically delivers electricity to homes and businesses — separate from the company that sells you electricity.

It is important to understand that a DNO is not the same as your energy supplier.

How solar changes the way electricity flows

Traditionally, electricity only moved from the grid into properties. When solar panels are installed, that flow can change. Solar systems often produce more electricity than the household is using in real time, especially during sunny summer days. The excess is fed back into the local grid rather than being wasted.

This applies to both:

• Homes with rooftop solar panels
• Businesses with larger commercial solar systems

Why the DNO needs to be involved

The DNO’s job is to make sure the local electricity network can safely handle that extra generation. If too many systems export electricity in the same area simultaneously, it can cause voltage fluctuations that affect nearby properties. To manage this, the DNO monitors things like:

• How much electricity is being exported into the grid
• Whether local cables or transformers could become overloaded
• Voltage levels across the network

Because of this, solar systems are usually registered with the local DNO. Smaller domestic installations are often simply notified after installation, while larger systems — including most commercial projects and larger residential solar systems — may require formal approval before work can begin.

A DNO solar application is the formal process of registering your solar installation with the local electricity network. It tells the DNO what type of system is being installed, how powerful it is, and how much electricity it could potentially export.

The application allows the DNO to check that:

• The local network can support the additional generation
• Voltage levels will remain stable for nearby properties
• The system is correctly documented for future upgrades and inspections

There are two types of application, depending on the size and export capacity of the system: G98 notification and G99 approval. These are explained in detail in the next section.

Most homeowners and businesses do not need to worry about the technical codes behind grid applications. However, you may hear installers mention G98 or G99 when discussing your system design — and it is worth understanding what these mean.

The difference mainly depends on how powerful the system’s inverter is and how much electricity it could export to the grid.

Single-phase properties (most homes) — usually G98

Most UK homes run on a single-phase electricity supply, and many residential solar systems fall within the G98 limit of 3.68 kW per phase. In these cases, the installer can proceed with installation and notify the DNO afterwards. There is no waiting period, and the process does not affect the installation timeline.

Three-phase properties (most businesses) — often G99

Commercial buildings usually have a three-phase electricity supply, which increases the G98 threshold to 11.04 kW. However, many commercial solar installations exceed even this threshold. In those cases, a G99 application is required, and the DNO may:

• Approve the system as designed
• Apply export limits
• Request small network upgrades

When G99 applications are most common

G99 approval is usually required for:

• Larger residential systems with inverters above 3.68 kW on single-phase properties
• Most commercial solar installations
• Battery systems capable of exporting electricity to the grid
• Hybrid solar-battery systems that exceed export thresholds

The difference between G98 and G99 is not about whether a solar system is better or worse. It simply ensures that the system’s output matches what the local grid can safely handle.

The UK is divided into licensed distribution network areas, each managed by a different DNO. Solar4Good’s in-house DNO team has submitted over 2,000 DNO applications across all of these network areas.