G98 vs G99: Which Application Do You Need?
The key difference is capacity. G98 is for systems up to 3.68kW (single-phase). G99 is for anything larger. Here's how to determine which you need.
Check Grid CapacityG98 vs G99 at a Glance
| Feature | G98 | G99 |
|---|---|---|
| Capacity Limit | ≤16A per phase (3.68kW single / 11.04kW three-phase) | >16A per phase (No upper limit) |
| Process Type | Connect & Notify | Apply & Connect |
| DNO Approval Needed? | No - install first | Yes - before install |
| Application Fee | £0 | £220 - £8,000+ (varies by DNO & size) |
| Timeline | Immediate install Notify within 28 days | 45-65 working days (Fast Track: 10-20 days) |
| Equipment Required | Type Tested inverter | Type Tested (recommended) |
| Typical Use | Residential solar Small battery systems | Commercial solar, solar farms Large battery, V2G |
Understanding the 16 Amp Threshold
The dividing line between G98 and G99 is 16 Amps per phase. This translates to:
Single-Phase Supply
3.68 kW
230V × 16A = 3,680W
Most UK homes have single-phase. A typical 3.6kW solar inverter just fits under G98.
Three-Phase Supply
11.04 kW
230V × 16A × 3 = 11,040W
Some larger homes and commercial properties have three-phase, allowing bigger G98 systems.
Important: Aggregate Capacity
The 16A limit applies to total generation capacity at your property, not individual devices. If you have a 3kW solar inverter and add a 2kW battery inverter, your aggregate is 5kW - which exceeds G98 and requires G99.
Common Scenarios: G98 or G99?
G98 (Connect & Notify)
Standard home solar (≤3.6kW inverter)
12 panels with a 3.6kW inverter = G98
Solar + DC-coupled battery
Hybrid inverter outputting max 3.6kW to grid = G98
Three-phase home (≤11kW)
10kW system on 3-phase supply = G98
G99 (Apply First)
Solar + AC-coupled battery
3.6kW solar + 5kW Powerwall = 8.6kW total = G99
Commercial rooftop solar
Any system over 3.68kW (single-phase) = G99
Solar farms & large BESS
Always G99 - typically megawatt scale
V2G (Vehicle-to-Grid) chargers
Bi-directional 7kW charger that exports = G99
G99 Fast Track: The Middle Ground
If your system exceeds G98 limits but is under 32A (7.36kW), you may qualify for G99 Fast Track. This uses export limitation (G100) to cap your grid export at 16A while allowing higher total capacity.
| Fast Track Type | Total Capacity | Export Limit | Example |
|---|---|---|---|
| SGI-1 | ≤16A (3.68kW) | No limit needed | 1.5kW solar + 2kW battery |
| SGI-2 | ≤32A (7.36kW) | ≤16A (3.68kW) | 3.68kW solar + 3.68kW battery with G100 limiter |
| SGI-3 | ≤60A (13.8kW) | ≤32A (7.36kW) | Large residential with impedance testing |
Fast Track typically takes 10-20 working days for approval, compared to 45-65 days for full G99.
G98 vs G99 Costs (2025/2026)
G98 Costs
£0
No DNO application fee. Your installer may charge £50-150 for completing the notification paperwork.
G99 Costs
Fees vary by DNO. Additional costs may apply if grid reinforcement is required.
Planning a Solar or Battery Installation?
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Check Grid CapacityFrequently Asked Questions
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