When you install solar panels in the UK, you can’t just connect them straight to the grid. The Distribution Network Operator (DNO) must be involved to make sure everything is safe and compliant. Depending on the size of your system, you’ll need either a G98 or G99 application. This guide explains the differences, what’s involved, and how UK homeowners can navigate the process smoothly.
What is a DNO application?
A DNO application is the process of notifying your local grid operator about a new solar installation. DNOs manage the electricity network in your area, and their approval ensures your system can connect safely without affecting other users. Applications check your system’s capacity, connection type, and export potential. Without approval, you risk fines, voided warranties, or being unable to export energy to the grid. For homeowners, a DNO application is a legal and practical requirement before your solar panels start generating electricity.
Do I need a G98 or a G99?
The type of DNO application depends on your system size and complexity. G98 covers smaller domestic systems, typically up to 3.68 kW per phase. It’s designed for standard rooftop solar where the risk to the network is low. G99 is for larger or more complex setups above 3.68 kW per phase. This includes bigger homes, shared systems, or commercial properties. Choosing the right application matters because the rules, timing, and technical requirements differ significantly. Using the wrong process can cause delays and extra costs.
What is a G98?
G98 is often called the “connect and notify” route. For most UK homes with standard rooftop panels, it’s the simplest and fastest option. After installation, your installer notifies the DNO, who checks the information and confirms your system meets safety standards. G98 doesn’t usually require pre-approval before installation, making it quicker for domestic systems. The process still requires accurate documentation, including system size, inverter details, and export limits. Homeowners benefit from a straightforward approach while remaining compliant and able to export energy safely.
What is a G99?
G99 is for larger systems or setups with higher export potential. Unlike G98, you must submit a G99 application before installation. The DNO reviews the technical design, protection settings, and impact on the local grid. This ensures that the larger system won’t cause voltage issues or overload circuits. Approval may take longer and sometimes requires additional network reinforcement or restrictions on export. For homeowners with bigger projects or multi-phase systems, G99 compliance is essential before any panels go live.
To make things a bit more obvious, here are some examples.
| System Size / Type | Export to Grid? | Application Route | Notes / Key Points |
|---|---|---|---|
| Up to 3.68 kW per phase (single-phase domestic) | Yes / No | G98 | Most standard rooftop installations. “Connect and notify” approach; installer usually handles notification after installation. |
| Up to 3.68 kW per phase with fast-track type-tested inverter | Yes | G98 Fast-Track | Approval can be quicker if inverter is type-tested and export limited; reduces administrative delays. |
| Above 3.68 kW per phase (domestic multi-phase or larger residential) | Yes | G99 | Pre-approval required before installation. DNO checks technical design, protection settings, and network impact. |
| Above 3.68 kW per phase (commercial, shared building, or high export potential) | Yes | G99 | Complex review often needed; may require network reinforcement or export restrictions. |
| Any system, export disabled / battery-only / backup-only | No | Usually not required | Systems that do not export may not need formal DNO application, but installer verification recommended. |
How to apply for a G98 or a G99
Both G98 and G99 applications require specific paperwork. Here’s everything broken down step by step:
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Gather your system information: total system size (kW), number of phases, inverter make/model, and panel specifications.
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Find your MPAN: locate your Meter Point Administration Number on your electricity bill; this identifies your property to the DNO.
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Check export settings: determine if your system will export electricity to the grid and whether export limiting is required.
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Prepare site diagrams: include single-line diagrams showing inverter location, battery (if any), and grid connection points.
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Collect type-test certificates: required for G99 applications and sometimes for fast-track G98 systems.
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Complete the application form: ensure all details match your system specifications; inaccuracies can delay approval.
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Submit via your installer: most installers handle submission, though you may need to provide authorisation.
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Track approval and respond to queries: DNO may request clarifications or modifications before granting approval.
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Confirm export limits: once approved, verify permitted export capacity and update system settings if required.
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Commission your system: install panels, inverters, and batteries (if applicable), then test operation according to DNO approval.
Costs and timelines
G98 applications are usually quick and low-cost, often handled entirely by your installer. Approval can come within days. G99 is more involved, with potential additional costs if network upgrades are needed. Timelines vary depending on the DNO, complexity of the system, and workload, but G99 can take weeks to months. For homeowners, planning ahead is essential. Budgeting for application costs and potential delays helps ensure the installation proceeds smoothly.
Once the DNO reviews your application, they can approve it, impose export limits, or request changes. For G98, you usually receive confirmation that you can export up to the allowed limit. G99 may require additional steps before connection. After approval, your installer can complete the commissioning process, and your system can start generating energy safely. Monitoring your system ensures it runs within the approved parameters and prevents issues with the grid.
Common Mistakes and How to Avoid Them
Many homeowners run into problems by missing deadlines, underestimating system size, or submitting the wrong forms. Another common mistake is thinking G98 and G99 are interchangeable—using the wrong application can cause delays, extra costs, or even require resubmission.
Other pitfalls include:
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Incorrect MPAN details: A small typo can prevent the DNO from identifying your property correctly. Always double-check your meter number.
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Mismatched system specifications: Submitting inverter, panel, or export capacity details that don’t match your actual setup can trigger DNO queries.
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Assuming self-submission is simple: While technically possible, homeowners often underestimate the complexity of G99 applications; working with a certified installer reduces stress and errors.
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Ignoring export limits: Some homeowners expect unrestricted export; exceeding approved limits can lead to compliance issues or penalties.
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Overlooking multi-phase or commercial considerations: Larger homes or shared buildings may need G99 even if the panels are roof-mounted.
Working with a certified installer, checking all documentation carefully, and reviewing your system details against your application can prevent most delays and headaches. Essentially, preparation and attention to detail are the simplest ways to keep your DNO application process smooth.
