If your photovoltaic system connects to the public electricity network, the installation usually involves your Distribution Network Operator (DNO) and the rules that govern connection/notification. In the UK, these are commonly described under Engineering Recommendations G98 and G99 for smaller vs larger generation (and, in many cases, storage).
G98 and G99 are UK connection processes for small-scale generation and storage connecting in parallel to the electricity network. In simple terms, smaller systems that meet G98 criteria can typically be installed and then notified to the DNO, while larger systems or those outside G98 requirements may need a G99 application approved before installation.
What is a DNO (and why should you care)?
Your DNO is the company that operates the electricity distribution network in your area. When you add generation (solar PV) or storage, the network operator may need to be informed so they can manage safety and network constraints.
G98 vs G99: the practical difference
National Grid’s connections guidance describes G99 processes applying where you install generation/storage above 16A (3.68kW) per phase, or where it does not meet G98 requirements.
A recent UK explainer summarises the homeowner-facing workflow like this:
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G98: smaller systems—install first, then installer notifies the DNO (often within a set timeframe)
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G99: larger systems and many batteries—application usually needs approval before installation
Bottom line: your installer should tell you whether your design is G98 or G99 and what that means for timeline and paperwork.
What paperwork should you expect?
Ask for:
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Confirmation of whether the install is treated as G98 or G99
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Evidence that the DNO notification/application has been submitted (and any response)
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Export limitation details if applicable (some systems limit export to meet constraints)
MCS also provides installer resources around notifying DNOs, including G98 forms and guidance.
FAQs
What’s the difference between G98 and G99?
G98 is generally used for microgeneration that meets its criteria; G99 is used for systems above 16A (3.68kW) per phase or those not meeting G98 requirements, and often involves a more formal connection process.
Do I need DNO approval before installation?
It depends on system size and whether it meets G98. Many larger systems or those involving storage may fall under G99 and may need approval before installation.
Will my installer handle the DNO steps?
Most reputable installers manage the DNO notification/application and provide documentation—ask for it explicitly in your quote checklist.
When you request PV quotes, ask: “Is this G98 or G99, and will you provide the DNO paperwork after commissioning?”