G98 vs G99
⚡ G98 vs G99: What’s the Difference?
When installing solar PV or battery storage in the UK, your system must comply with engineering standards set by the Energy Networks Association (ENA). These standards ensure your equipment connects safely to the public electricity distribution network.
The two key standards are G98 and G99, and the one you need depends mainly on system size.
🟢 What is G98?
G98 covers small microgeneration systems up to 16A per phase, which is roughly 3.68 kW on a single‑phase supply. It’s designed for simple, low‑impact installations.
Key points:
- Applies to most standard domestic solar PV systems.
- You can install the system and then notify the DNO within 28 days.
- The process is quick and usually requires no prior approval.
🔵 What is G99?
G99 applies to any system larger than 16A per phase, including:
- Larger domestic solar arrays
- Bigger battery storage systems
- Commercial installations
- Three‑phase systems
Key points:
- You must apply before installation and wait for DNO approval.
- The DNO may need to assess grid impact or upgrade local infrastructure.
- The process is more detailed and can take weeks to months.
🧭 Why the Difference Matters
The UK grid wasn’t originally designed for widespread small‑scale generation. G98 and G99 help DNOs ensure:
- Grid stability
- Safety
- That local networks aren’t overloaded
🏡 Which one do you need?
Here’s a simple rule of thumb:
- Most UK homes with typical 3–4 kW solar systems → G98
- Homes with larger systems (e.g., 5–10 kW), big batteries, or 3‑phase supplies → G99
- Commercial or agricultural installations → G99