G98 vs G99 Applications: Grid Connection for Solar Arrays

When installing solar panels on your UK property, connecting to the national grid requires proper authorisation through either a G98 or G99 application. Understanding the difference between these two crucial forms can save you time, money, and potential complications during your solar installation journey. Whether you’re a homeowner in Manchester considering a modest rooftop array or a business owner in Birmingham planning a larger commercial installation, choosing the correct grid connection application is essential for legally exporting your excess solar energy back to the grid.

Understanding Grid Connection Applications

Grid connection applications are formal notifications or requests submitted to your Distribution Network Operator (DNO) before connecting any electricity-generating equipment to the national grid. In the UK, these applications ensure that local electricity networks can safely accommodate additional power generation without compromising grid stability or safety.

Your DNO—whether it’s UK Power Networks in London, Northern Powergrid in Yorkshire, or Scottish Power Energy Networks in Glasgow—requires this documentation to:

• Assess the impact of your solar installation on local grid infrastructure
• Ensure compliance with engineering standards and safety regulations
• Coordinate any necessary network upgrades or reinforcements
• Establish proper metering and export arrangements

The type of application you need depends primarily on the size and capacity of your proposed solar array, with G98 covering smaller installations and G99 addressing larger, more complex systems.

G98 Applications: For Smaller Solar Installations

A G98 application, formerly known as G83, is a simplified notification process for connecting small-scale generation equipment to the electricity distribution network. This streamlined approach applies to solar installations with a total inverter capacity of 3.68kW per phase or less (11.04kW for three-phase connections).

Key Features of G98

The G98 process is designed to be straightforward and accessible for typical residential solar installations:

• Notification-based system: Rather than seeking permission, you’re informing the DNO of your installation
• Fast processing: DNOs typically acknowledge G98 notifications within days
• No application fees: Most DNOs don’t charge for G98 submissions
• Simplified technical requirements: Standard inverters meeting G98 specifications are automatically approved

For a typical three-bedroom semi-detached house in Leeds with a 3.5kW solar array, a G98 application would be perfectly suitable. The process involves your MCS-certified installer submitting the notification either before or within 28 days after commissioning the system.

G99 Applications: For Larger Solar Arrays

G99 applications, which replaced the former G59 standard, are required for solar installations exceeding the G98 thresholds. This more comprehensive application process applies to systems with inverter capacities above 3.68kW per phase, making it essential for larger residential properties, commercial buildings, and solar farms.

The G99 Process Explained

Unlike G98’s notification approach, G99 requires formal approval before connection:

• Pre-application stage: Submit detailed technical specifications and single-line diagrams
• DNO assessment: Network analysis to determine connection feasibility
• Formal offer: DNO provides connection terms, costs, and any required network upgrades
• Acceptance and payment: You accept the offer and pay any associated fees
• Installation and commissioning: Complete the installation following DNO requirements

A commercial property in Bristol installing a 50kW rooftop solar array would need to navigate the G99 process, potentially facing connection costs ranging from £500 to several thousand pounds, depending on local network capacity and required upgrades.

Key Differences Between G98 and G99

Understanding the distinctions between these two application types helps ensure you budget appropriately and set realistic timelines for your solar project:

Capacity Thresholds

• G98: Maximum 3.68kW per phase (single-phase) or 11.04kW (three-phase)
• G99: Any installation exceeding G98 limits, up to 50MW and beyond

Processing Times

• G98: Typically 5-10 working days for acknowledgement
• G99: 45-65 working days for initial assessment, potentially longer for complex projects

Costs

• G98: Usually free of charge
• G99: Application fees from £350-£1,500, plus potential network reinforcement costs

Technical Requirements

• G98: Standard type-tested inverters, basic protection settings
• G99: Detailed protection settings, potential for witness testing, power quality assessments

Choosing the Right Application for Your Solar Project

Selecting between G98 and G99 isn’t always straightforward, particularly for installations near the threshold. Consider these factors when planning your solar array:

System Sizing Considerations

Whilst maximising solar generation is appealing, staying within G98 limits can offer significant advantages. A 3.6kW system might generate slightly less electricity than a 4kW array, but avoiding G99 requirements could save thousands in connection costs and reduce installation timeframes by months.

For properties in Edinburgh or Newcastle with limited roof space, a G98-compliant system often provides the best return on investment. However, farms in rural Lincolnshire or large warehouses in the West Midlands might benefit from larger G99 installations despite higher upfront costs.

Future Expansion Plans

If you’re considering starting with a modest installation but plan to expand later, discuss this with your installer. Some homeowners in areas like Surrey or Hertfordshire initially install G98-compliant systems, then add battery storage or additional panels later under separate applications.

The Application Process: Step by Step

Whether pursuing G98 or G99, understanding the application process helps ensure smooth project delivery:

G98 Application Steps

1. Installer preparation: Your MCS-certified installer gathers system specifications
2. Online submission: Complete the DNO’s online G98 notification form
3. Documentation: Upload commissioning certificates and electrical schematics
4. DNO acknowledgement: Receive confirmation of notification acceptance
5. Begin exporting: Start feeding excess energy to the grid immediately

G99 Application Steps

1. Feasibility study: Assess site suitability and grid capacity
2. Pre-application enquiry: Submit technical details for DNO review
3. Receive budget estimate: DNO provides indicative costs and timescales
4. Full application: Submit comprehensive technical documentation
5. DNO assessment: Network studies and impact analysis
6. Connection offer: Review and accept formal terms
7. Installation: Complete works according to DNO specifications
8. Commissioning tests: Verify compliance with G99 requirements
9. Final connection: DNO approves grid connection and export

Common Challenges and Solutions

Both application types can present challenges, but understanding common issues helps avoid delays:

Network Constraints

In areas with high solar penetration, such as Cornwall or Devon, local networks might be approaching capacity. Solutions include:

• Installing export limitation devices to restrict grid feed-in
• Adding battery storage to maximise self-consumption
• Accepting partial export agreements
• Contributing to network reinforcement costs

Documentation Requirements

Incomplete or incorrect documentation causes most application delays. Ensure your installer provides:

• Accurate single-line diagrams
• Manufacturer’s inverter test certificates
• MCS installation certificates
• Electrical Installation Certificates (EIC)

Regional Variations and DNO Specifics

Whilst national standards govern G98 and G99 applications, regional variations exist across the UK’s 14 DNO areas. Western Power Distribution (covering the Midlands, Southwest, and Wales) might have different processing times compared to Electricity North West (covering Manchester and the Lake District).

Some DNOs offer enhanced services, such as Scottish and Southern Electricity Networks’ online connection surgeries, whilst others provide detailed heat maps showing network capacity. Understanding your local DNO’s specific requirements and support services can streamline your application process.

Conclusion

Choosing between G98 and G99 applications represents a crucial decision in your solar installation journey. Whilst G98 offers a simpler, cost-effective route for smaller installations under 3.68kW per phase, G99 enables larger systems that can maximise generation potential despite additional complexity and costs. By understanding these requirements early in your planning process, working with experienced MCS-certified installers, and engaging proactively with your DNO, you can ensure your solar array connects to the grid efficiently and legally. Whether you’re installing panels on a terraced house in London or a commercial unit in Manchester, the right application process paves the way for successful solar generation and export for decades to come.