The DNO Application Process: A Step-by-Step Guide for Solar Installers

Every grid-connected solar installation in the UK needs some form of DNO notification or application. But the process isn't always straightforward. Different system sizes have different requirements, each DNO has its own portal, and missing a single document can delay approval by weeks.

This guide walks you through the entire process from start to finish, so you know exactly what to expect at every stage.

Step 1: Determine Whether You Need G98 or G99

The first question is always the same: how big is the system?

• G98 (up to 3.68 kW per phase): a simple notification process. For single-phase connections this means up to 3.68 kW, and for three-phase up to 11.04 kW total. You notify the DNO after commissioning, with no pre-approval needed.
• G99 (above 3.68 kW per phase): a full application that must be submitted and approved before the system is commissioned. This applies to most domestic solar installations over ~4 kW on single-phase.

Step 2: Gather Your Documents

For a G98 notification, you'll typically need:

• Customer name and address
• MPAN (Meter Point Administration Number)
• Inverter make, model, and rated output
• Total installed generation capacity
• Commissioning date

For a G99 application, you'll need all of the above plus:

• Single Line Diagram (SLD): a technical drawing showing how the generation equipment connects to the supply
• Letter of Authority (LOA): signed by the property owner, authorising you or your agent to act on their behalf with the DNO
• Full equipment specifications, including inverters, batteries, EV chargers, and any other connected generation or storage
• Proposed export capacity
• Site supply details, including phase type, cutout rating, and existing supply capacity

Step 3: Identify the Correct DNO

The UK is divided into regional distribution areas, each managed by a different DNO. The six main operators are:

• National Grid (NGED): South West, South Wales, West Midlands, East Midlands
• UK Power Networks (UKPN): South East, East of England, London
• Scottish and Southern (SSEN): Central and North Scotland, Southern England
• SP Energy Networks (SPEN): South Scotland, North Wales, Merseyside, Cheshire
• Electricity North West (ENW): North West England
• Northern Powergrid (NPG): North East England, Yorkshire

You can identify the DNO from the first two digits of the customer's MPAN, or use the postcode lookup on our DNO coverage map.

Step 4: Submit the Application

Each DNO has its own portal for receiving applications:

• National Grid: uses the ConnectRight portal
• UKPN: G99 applications through their online portal; G98 via the ENA portal
• SSEN: uses their own online application system
• SP Energy Networks: applications submitted through their connections portal
• Electricity North West: their own dedicated portal
• Northern Powergrid: applications via their online connections system

For G99 applications, you'll upload your SLD, LOA, and equipment details during submission. Most portals will issue a reference number immediately, so keep this safe as you'll need it for all future correspondence.

Step 5: Wait for the DNO to Process Your Application

Once submitted, the application goes through the DNO's assessment process. Timelines vary depending on the DNO, system size, and local network capacity:

G98 Notifications

These are usually acknowledged within a few working days. Since G98 is a post-commissioning notification, you don't need to wait for approval before installing.

G99 Applications: Typical Timelines

• Under 50 kW (Fast Track eligible): most DNOs aim for 25 to 45 working days, though this varies significantly between operators
• 50 kW to 1 MW: typically 45 to 65 working days
• Over 1 MW: can take 3 to 6 months depending on network studies required

During this period, the DNO's design engineer reviews the application against the local network capacity. They may come back with questions, request additional information, or flag issues with the proposed connection.

Step 6: Respond to Any Information Requests

It's common for the DNO to request additional information after initial submission. Typical requests include:

• Updated or corrected SLD
• Clarification on export limiting arrangements
• Additional equipment specifications
• Confirmation of supply phase type or cutout rating

Responding quickly is critical. Most DNOs pause your application's clock while waiting for a response, so delays on your end directly extend the overall timeline.

Step 7: Receive Approval (or an Offer Letter)

For straightforward domestic G99 applications, you'll typically receive a connection approval letter confirming the DNO is happy for the installation to proceed.

For larger or more complex installations, the DNO may issue an offer letter instead. This outlines any conditions, network reinforcement costs, or export limitations. You'll need to accept the offer (and pay any charges) before the connection can proceed.

Export Limiting

In some cases, the DNO will approve the connection but impose an export limit lower than what was requested. For example, you may request 10 kW export but only be approved for 6 kW. In these cases, you'll need to install export limiting equipment (G100 compliance) and provide an updated SLD showing the limiting arrangement.

Step 8: Commission and Notify

Once you have approval:

• Complete the installation and commission the system
• Submit a commissioning confirmation to the DNO (required for G99)
• The DNO will then issue an export MPAN or confirm the connection is live

The export MPAN is essential for your customer. They'll need it to register with an energy supplier for the Smart Export Guarantee (SEG) and start getting paid for their exported electricity.

Common Reasons for Rejection or Delay

Based on thousands of applications we've processed, these are the most frequent causes of problems:

• Incorrect or missing LOA: name or address doesn't match the MPAN records
• SLD errors: incorrect wiring arrangement, missing components, or doesn't match the equipment list
• Wrong MPAN: especially common on new-build sites or properties with multiple meters
• Incomplete equipment details: missing battery or EV charger specifications when they're part of the installation
• Network capacity issues: the local network can't support the proposed export, leading to export limiting or reinforcement requirements

How Long Does the Whole Process Take?

End to end, here's what a typical domestic G99 application looks like:

Can You Speed Up the Process?

You can't control how fast the DNO processes your application, but you can avoid the most common delays:

• Get your documents right first time: correct LOA, accurate SLD, complete equipment list
• Respond to information requests immediately: every day you delay adds a day to the timeline
• Use the correct MPAN: verify it against a recent electricity bill before submitting
• Consider using a specialist: services like ours know exactly what each DNO expects and can avoid the common pitfalls that cause rejections