Solar, battery & DNO registration blog

Export limitation: fitting a larger system on a limited connection

An export limiting scheme caps how much power a site can send to the grid. It lets you fit a larger array or battery than the local network could otherwise accept at full export, which can make the difference between a job going ahead and a costly network upgrade.

Export limiting schemes must meet Engineering Recommendation G100 and the DNO has to agree to them before the system relies on the limit. A system whose inverter capacity is over the G98 limit normally still needs a G99 application, but the DNO can assess it on the agreed export figure rather than the full installed capacity.

The application needs the export limit you are asking for, details of the limiting device and how it is set up, plus the full rating of all generation and storage on site. Get these right first time and the assessment is far more straightforward.

Ask us about an export-limited system

The ENA Type Test Register: why it matters for G98

The Energy Networks Association keeps a register of inverters and battery systems that have been type tested to show they meet the G98 or G99 requirements. For a G98 notification the equipment must be type tested, so the register is the first thing to check.

Look up the exact model number, not just the product range. Manufacturers often sell several versions of an inverter and only some may be listed. A data sheet on its own is not enough.

If the equipment is not on the register, the G98 route is not available and the installation will need a G99 application with additional test evidence. Checking before you order kit saves delays later.

Not sure your kit is listed? Ask us

G99 Type A, B, C and D: what the categories mean

G99 sorts generation into four types by size and connection voltage. In Great Britain, Type A covers 0.8kW up to less than 1MW, Type B covers 1MW up to less than 10MW and Type C covers 10MW up to less than 50MW. Type D is 50MW or more or anything connected at 110kV or above.

Almost every rooftop solar and battery system an installer fits will be Type A. Where Type A equipment is type tested, the application is simpler because much of the technical evidence is already on the ENA register.

Type B and above bring more detailed technical data, testing and compliance steps. These are usually large commercial or ground-mounted schemes and need planning well ahead of the build.

Ask us about your G99 application

Multiple installations on one street: why G98 notification is not enough

New-build estates, social housing programmes and blocks of flats often see solar or batteries fitted to many properties close together. Each system may be small enough for G98 on its own, but together they can have a real effect on the local network.

For multiple installations in a close geographic area, G98 requires you to apply to the DNO before installation and wait for its response, rather than notify within 28 days of commissioning. Leaving it until after the systems are fitted risks delays to switch-on.

Plan it early: collect the address and MPAN for each property, the equipment for each system and the installation programme, then submit the application before work starts.

Planning a multi-site project? Talk to us

Solar, batteries, EV chargers and heat pumps on one site

More customers now want solar, a battery, an EV charger and a heat pump together. Solar and batteries are generation and storage, so they go through G98 or G99. EV chargers and heat pumps add demand and are notified to the DNO separately.

When they are fitted together, the DNO looks at the whole picture. A large new demand on a small supply may need a check of the main fuse or a supply upgrade, while the solar and battery affect what the site can export.

Coordinate the paperwork so each notification or application reflects everything planned for the property. It avoids surprises when the last piece of equipment goes in.

Hand us the solar and battery side

Commercial solar: what changes with a larger G99 application

Commercial roofs can take far larger arrays than homes, which means a G99 application with more for the DNO to assess. On bigger systems the DNO may need to study the local network before it can agree to the connection.

The DNO's response may be a formal connection offer. If the network needs reinforcement, the offer can include costs and conditions that must be accepted before the system can connect. Build this into the customer's budget and timeline from the start.

Accurate site details, single-line diagrams and equipment data make a real difference at this scale. Export limitation is also worth considering where the network is constrained.

Ask us about commercial applications

Do I need to tell my DNO about a home battery?

Yes. A battery can export power back to the grid, so DNOs treat storage in much the same way as solar generation. Whether you are installing a battery on its own or adding one to an existing solar system, it needs to be notified or approved.

The route follows the same size rule as solar: G98 for smaller systems (up to 16 amps per phase) and G99 for larger ones. Because inverter and battery ratings count towards the total on site, adding a battery to an existing array can sometimes push a system over the G98 limit and into G99.

Check the combined rating before work begins, not after, so you know which route applies.

Ask us about battery registration

Who is responsible for registering a solar or battery installation with the DNO?

The installer is normally responsible. DNO notification or approval is part of commissioning and the right route must be followed before the system is switched on: a G98 notification for smaller systems or G99 approval first for larger ones.

If a system was installed without being registered, it can still be notified or applied for. Contact the DNO or ask a service like Go DNO to do it for you. Late is better than never.

Keep a copy of the confirmation or approval. It is useful for your records and for the customer, their energy supplier or a future buyer of the property.

How to find your DNO from your MPAN

Your DNO depends on where the property is, not on who supplies the electricity. The easiest way to find it is from the MPAN, the meter point number on the customer's electricity bill.

Look for the 13-digit core MPAN. The first two digits identify the network area:

Northern Ireland is served by NIE Networks and has its own process. No MPAN to hand? The Energy Networks Association's "Find my network operator" tool will find your DNO from the property's postcode.

Six common mistakes that delay a G99 application

Most delays come from avoidable errors. Watch out for these:

• Connecting before approval. A G99 system must be approved first.
• Missing the battery. Every inverter and battery on site counts towards the total.
• Incomplete data sheets. The DNO needs the manufacturer's documents for the inverter and equipment.
• An unclear single-line diagram. It should match the equipment actually being installed.
• Wrong address or MPAN. Check both against the electricity bill.
• Slow replies. DNO queries left unanswered can stall an application for weeks.

Getting these right first time is the quickest way to approval.

Why solar and battery installers outsource DNO applications

DNO applications are essential, but they are not the work installers are in business to do. Forms, data sheets, diagrams and chasing queries all take time away from quoting and installing.

• Save time. Hand over the system details and get on with the next job.
• Fewer delays. Applications prepared by specialists are more likely to be right first time.
• Predictable cost. One price of £99.00 for each G98 notification or G99 application.
• Less admin, always up to date. We submit and follow up with the DNO, keep you informed at every stage of the process and pass you the confirmation for your records.

Go DNO works with installers across the UK.

Outsource your DNO

G98 or G99: which does my solar or battery installation need?

Every grid-connected solar PV or battery system has to be made known to the local District Network Operator (DNO). How you do that depends on the size of the system.

G98 covers smaller generation, up to 16 amps per phase (about 3.68kW on a single phase). You connect first, then notify the DNO within 28 days of commissioning.

G99 covers anything larger. You must apply to the DNO and receive approval before the system is connected. Larger systems may need extra studies or network work.

Batteries and inverters count towards the total, so add up everything on site. If you are unsure, ask before starting work, because connecting a G99 system without approval can mean it has to be switched off.

What is a DNO and why does it need to know about my solar panels and battery?

A District Network Operator owns and runs the local electricity network that brings power to homes and businesses. Different regions have different DNOs and yours depends on where the property is.

Solar panels and batteries can push power back onto that network. The DNO needs to know what is connected so it can keep voltages safe, plan capacity and protect the people working on the network.

Registering also helps you: it keeps your installation compliant and supports export arrangements and the paperwork that comes with commissioning.

What you need to register a solar PV or battery system with your DNO

Having the right details ready makes registration quicker. Gather the following before you start:

• The installation address and the MPAN from the electricity meter
• Make, model and rated output of the inverter
• Solar panel details and total installed capacity
• Battery storage make, model and capacity, if fitted
• The installer's details and the commissioning date

Send these to Go DNO and we will prepare the G98 notification or G99 application for you.

Ask us about registration

What is the 3.68kW limit? Understanding the G98 threshold

The G98 limit is set at 16 amps per phase, not in kilowatts. On a standard single-phase supply of around 230 volts, 16 amps works out at roughly 3.68kW. That is why 3.68kW is the figure most installers quote for the point where a system moves from G98 to G99.

The limit applies to the combined rating of the generating and storage equipment connected at the property, not just the solar panels. A 3.6kW solar array with a separate battery inverter can take a site over the line, so add up everything that can export before deciding which route applies.

If the total is close to the limit, check the rating plates and datasheets rather than the headline panel capacity. The inverter's rated AC output is what counts.

Not sure which route applies? Ask us

G98 notifications: the 28-day rule for installers

A G98 system can be connected without waiting for approval, but the DNO must be told. The notification is due within 28 days of commissioning, so it needs to be part of the job closing process and not something left until later.

The notification normally needs the installation address, inverter and battery details, the installed capacity and the commissioning date. Having these to hand at handover makes the notification quick to complete.

G99 is different. For larger systems the application must be made and approved before the system is connected, so the two routes need to be planned differently from the start of the job.

Let us handle your G98 notifications

What happens if a G99 system is connected without approval?

Connecting a G99 system before the DNO has approved it breaches the network operator's connection requirements. In practice the DNO can ask for the system to be switched off until the application has been dealt with, which means an unhappy customer and a return visit.

There can be knock-on problems too. Missing DNO approval can hold up commissioning paperwork, MCS certification and export payments, all of which customers expect to be sorted promptly.

If it has already happened, do not wait. Make the application as soon as possible and keep the customer informed. A system that has been regularised promptly is far easier to resolve than one left unreported.

Need a G99 application made quickly?

Single-phase or three-phase: how does it affect G98 and G99?

The G98 limit is 16 amps per phase, so a three-phase supply allows a larger system to stay within G98 than a single-phase one. On a three-phase connection the limit works out at roughly 11kW in total, spread across the three phases.

That does not mean any three-phase system is automatically G98. The equipment has to be installed so that the generation is shared across the phases and the combined rating still has to stay within the per-phase limit. A single-phase inverter on a three-phase property is still limited by its own phase.

When in doubt, check the supply type and the inverter arrangement before ordering equipment. It is much easier to choose the right route at quotation stage than after installation.

Ask us about your installation

Smart Export Guarantee: does DNO registration come first?

The Smart Export Guarantee (SEG) lets customers with solar and some other small-scale generation be paid for the electricity they export to the grid. Most suppliers will want evidence that the installation has been properly certified and for most solar installations that includes confirmation that the DNO has been notified or has approved the connection.

That makes DNO registration a practical step in getting customers paid, not just a compliance exercise. Delays or missing paperwork can hold up the SEG application and leave the customer waiting.

Registering promptly and passing the confirmation to the customer as part of handover avoids those delays and makes for a smoother finish to the job.

Get your DNO applications done for you

Adding a battery to an existing solar system: what does the DNO need?

Retrofitting a battery is one of the most common jobs and it is easy to assume the original solar registration covers it. It does not. The DNO needs to know about the battery, because it changes what the site can export and how it behaves on the network.

Start by adding the battery inverter's rating to the existing equipment on site. If the combined total is still within the G98 limit, a G98 notification is normally enough. If it takes the site over the limit, a G99 application is needed before the battery is connected.

Whichever route applies, keep the details of both the original system and the new battery together so the application is accurate and complete.

Ask us about battery retrofits

J.O.E Solar: handing DNO applications to Go DNO

J.O.E Solar, based in Dinnington, is one of the installers we work with and they send us all of their DNO applications. For a solar and battery business, the time spent on G98 notifications and G99 applications is time not spent on the work that brings in customers.

In their words: “We use Go DNO for all of our DNO applications. It saves us valuable time allowing us to concentrate on sales and installations.”

That is exactly why we do what we do. You send us the system details and the site address, we prepare and submit the application, deal with the DNO and pass you the confirmation, so your team can stay focused on selling and installing.

Hand your DNO applications to us

Simplicity Solar: an invaluable service for a small company

Simplicity Solar is a small installer based in North Wales that uses Go DNO for all of its installations. For a small business, every hour counts and DNO registration is the kind of task that is easy to put off and awkward to get wrong.

Here is how they describe the service: “Invaluable service for a small company. I use Go DNO for all my installations. It's an excellent service at a great price.”

We handle any number of applications, large or small, so whether you complete a few installations a month or many, the process is the same: send us the details and we take care of the rest.

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