If you’re planning a DIY home solar or battery storage installation in the UK, knowing how to register your system with your local Distribution Network Operator (DNO) is essential. This process ensures your installation is safe and complies with regulations for grid-connected energy devices. Here’s a straightforward guide for homeowners. DIYers can register their system without depending on certified installers.
To register a DIY solar installation with the DNO in the UK, submit a G98 notification (free, for systems under 3.68kW AC) within 28 days of commissioning, or apply for G99 approval (for systems over 3.68kW) before you install. Both forms are available on the National Grid website. You do not need an MCS installer to submit them. You need your MPAN number, inverter make and model, total AC capacity, and a single-line wiring diagram.
| G98 | G99 | |
|---|---|---|
| System size | Up to 3.68kW AC (single phase) | Over 3.68kW AC |
| When to apply | After installation, within 28 days | Before installation |
| Processing time | 10-15 working days | 8-12 weeks |
| Cost | Free | Free (but DNO may charge for grid studies) |
| Can DNO reject? | No (notification only) | Yes (if grid is constrained) |
| Form available | National Grid G98 form | National Grid G99 form |
| DIY eligible? | Yes | Yes |
Plan the DNO route before you finalise the roof layout
Before I committed to a panel count and a roof drawing, I worked backwards from the DNO route. The thing that decides G98 versus G99 is the AC generation capacity per phase, not the number of panels you can fit on the roof. National Grid’s G98 guidance sets the single-phase boundary at 16A per phase, which is 3.68kW at 230V on type-tested kit. The wait for G99 approval is also why installer quotes tend to stop short of 4 kWp. Above that you are into G99, which has to be approved before you install.
So before I drew anything on the roof, I picked a candidate inverter and looked it up on the ENA Generator Type Test Register. That gave me the device reference number I would need on either form, and it confirmed the AC nameplate. From there, the roof layout became a sanity check rather than a guess: can the array fit, will it actually load that inverter, am I staying within G98, and if I am going G99, what export figure or export-limitation device am I declaring.
Roof orientation does not change the DNO category, but it changes the inverter you pick and how hard you push the AC limit. A south-facing roof can produce a sharper midday peak, so a strict 3.68kW AC system on a south roof may clip more than the same kit split east and west. A split layout often spreads the curve and may let a slightly larger DC array sit happily behind a G98-compliant inverter. This is design reasoning, not an official DNO rule, so model it with your own shading and tilt before you commit.
Flat roofs are a separate planning job. Row spacing, ballast, edge zones and a safe walking route around the array all eat usable space, so the panel count you can register is whatever survives the layout, not the maximum the roof area suggests. Get the roof drawing finished first, then take the resulting array DC and AC numbers to the DNO form. See mounting equipment for the practical side of fixings and rails.
Scaffolding timing is not a DNO rule, but it is the rebook you do not want. Before the boards go up, lock the full scope: panels and layout, cable route, isolator and inverter location, bird protection, and any provision for a future battery or hybrid inverter. If a G99 decision lands after the scaffold comes down, that can mean a second access visit and a redesign you were not planning for.
Battery-ready design feeds straight back into the form. If you might add storage later, picking a hybrid inverter up front, or planning how an AC-coupled battery will sit behind your meter, affects both export capacity and whether you need a separate export limitation device. The G99 form asks for the device reference number of any external export limitation kit, so it is worth deciding that early rather than retrofitting and re-notifying.
Determine Your System Size and DNO Application Type
The type of application depends on your solar system’s capacity:
- G98 Application: This is for smaller systems that produce up to 3.68 kW per phase (equivalent to 16A). For these, the DNO uses a “connect and notify” approach, meaning you can install your system first and inform the DNO afterwards. You have up to 28 days post-installation to submit the necessary documents.
- G99 Application: If your system exceeds 3.68 kW per phase, apply under G99. This application must be approved before installation, as larger systems can impact the local grid’s stability. The G99 process is more detailed and may require up to 8-12 weeks for approval.
Plug-in solar panels (up to 2kWp) have their own simplified notification route under the new UK regulations — no G98 or G99 required for compliant systems.
Gather the Necessary Information for the DNO
Before filling out your application, gather these essential details:
- System Specifications: Include technical information about your solar panels, inverters, and overall system capacity. These details help the DNO assess whether your setup can be safely connected to the grid. The crucial piece here is the inverter make and model number. Look up yours at the ENA type test register. Not sure which inverter to choose? Our guide covers the key specs to check.
- Schematic Diagram: A simple layout showing how your system connects to your property’s electrical infrastructure, including the location of the inverter and isolator switches.
- MPAN Number: This unique number identifies your electricity meter. It’s often found on your electricity bill and is required for the DNO application. You can also google “What’s my MPAN” and navigate to the nationalgrid.co.uk website to extract that data by your address.
Which DNO Covers Your Area?
Your DNO depends on your postcode. These are the main operators:
- UKPN (UK Power Networks) — London, South East, East England
- WPD / National Grid Electricity Distribution — Midlands, South West, Wales
- NPG (Northern Powergrid) — North East, Yorkshire
- SSEN (Scottish and Southern Electricity Networks) — Scotland, parts of Southern England
- ENW (Electricity North West) — North West England
- SP Energy Networks — Central and Southern Scotland, North Wales, Merseyside
You can find your DNO by entering your postcode at the Energy Networks Association website. Your MPAN number (found on your electricity bill) also identifies your DNO — the first two digits are the DNO code.
Submitting Your Application to the DNO
For G98 installations, you should submit the notification form within 28 days after installation. The submission must include your system’s technical specs and the schematic diagram. For G99 applications, you’ll submit a detailed form and await approval before installing. The DNO may ask for further information, so ensure all documents are accurate to prevent delays.
You can also cover this entire process online by following simple steps at the National Grid website.
Battery Storage Considerations
Suppose you plan to add battery storage, especially systems with backup functionality that can “island” (disconnect from the grid during power outages). In that case, you must inform the DNO as these setups require additional safety checks. Battery storage systems are becoming increasingly popular as they enhance self-sufficiency by storing excess solar energy for later use.
Importance of Timely and Accurate Applications
It is important to file your application promptly and accurately. DNOs have seen increased demand due to the rise in renewable installations, and processing times can be longer than expected. For G98, approval may take up to four weeks, while G99 could take several months, especially for larger or more complex systems.
Common Mistakes That Delay Your Application
- Wrong MPAN number: Check your bill, not your meter
- Inverter not on the ENA Type Test Register: Check before you buy — see the ENA type test register. Need help picking the right one? See our inverter selection guide.
- Missing single-line diagram: Draw it yourself, it does not need to be professional
- Submitting G98 when you need G99: Check total AC output, not panel wattage
- Not allowing enough time for G99: SSEN can take 45-60+ working days
Final Thoughts
Navigating the DNO application process is a key part of setting up a safe and compliant DIY solar system. Understanding your system’s requirements, gathering the proper documents, and engaging with your DNO early can ensure a smooth connection process. Once your DNO registration is sorted, you can also register to export surplus energy and earn from your generation. For a full picture of what financial support is available, see our UK Solar Panel Grants and Incentives 2026 guide.
