Guidelines & Regulations
G99 Explained: What It Means for Home Solar and Storage
A comprehensive guide to UK grid standards when your energy generation exceeds the standard residential G98 limit.
What is G99?
G99 is the regulatory standard for connecting generation equipment to the grid. While G98 is for small systems under 16A, G99 is essential for larger solar arrays and heavy-duty battery storage. It ensures that the local electricity network can safely handle the power your system generates.
Essential Insight
Disclaimer: This is for educational use only and not professional electrical advice. Always consult a certified solar engineer.
Standard Comparisons
G98 Boundary
Covers systems up to 3.68kW. Notification after setup.
G99 Boundary
For systems above 3.68kW. Full DNO permission required before start.
Installation Checklist
- 1. Verify total system kW output. 2. Locate your regional DNO. 3. Prepare technical data sheets. 4. Submit G99 application forms. 5. Secure official Connection Offer. 6. Sign and return terms. 7. Professional install. 8. Commissioning tests. 9. File your E6 certificate.
Common Inquiries
What is the approval timeline?
Most DNOs take 45 to 65 days to review applications. This varies by region and the current capacity of your local grid.
Are there costs for application?
Yes, DNOs usually charge a fee to process G99 forms and may charge for any necessary network upgrades to your area.
Official ENA Resource
Access the Energy Networks Association database for the latest Engineering Recommendations and certified equipment lists.
Navigating Engineering Recommendation G99
If you are upgrading your home with a large solar stack or multiple batteries that surpass G98 limits, the G99 process is your legal pathway. This article breaks down the nine essential steps to compliance for UK homeowners, ensuring your green energy transition is safe, legal, and fully approved.
Scope of G99
The G99 regulation applies to any energy system exporting more than 3.68kW single-phase or 11.04kW three-phase. It covers the technical requirements for protection, power quality, and operational control necessary for large-scale domestic generation and storage.
G98 Threshold
Limit is 3.68kW per phase via simple notify-after-install.
G99 Threshold
Applies above 3.68kW and requires pre-approval before project.
Mandatory G99 Checklist
- Confirm your DNO region. Calculate combined Solar and Battery kW. Ensure inverters are on the ENA approved list. Submit the G99 Standard Form. Receive and accept the Connection Offer. This guide is for educational info, not electrical advice.
LEGAL NOTICE
Connecting a high-capacity system without G99 approval violates the UK Distribution Code and can lead to immediate grid disconnection and fines.
Expert Answers
Can I bypass the G99 application?
No. If your peak generation exceeds 3.68kW, the application is a legal requirement for grid safety.
Who should file the forms?
While you can do it, we suggest your MCS-certified installer handles the G99 filing to ensure technical data accuracy.
External Links
- Find Your Local DNO. ENA Type Test Register. Ofgem UK Rules.
G99 Compliance Checklist
DNO connection offer secured
G99 registered and tested inverter used
System installed by a qualified professional
Completed G99 commissioning work
Final E6 certificate sent to the DNO
Frequently Asked Questions
Do I need G99 for small solar setups?
No, if the output is under 3.68kW, G98 applies. For anything larger, G99 is required before you begin the installation.
How fast do DNOs grant approval?
The standard wait time is around 45-65 working days, though fast-track options for certain Type A systems may be available.