G98 Inverter Calculator
Verify solar inverter eligibility under ENA Engineering Recommendation G98. Calculate export currents for single or three-phase systems against the UK 16A per phase limit to check if DNO notification can be completed after installation.
G98 Inverter Calculator
How to Use G98 Inverter Calculator
Verifying G98 eligibility is essential for UK residential microgeneration systems. This calculator determines whether a proposed inverter setup satisfies the simple "commission and notify" criteria. Follow this workflow to evaluate compliance:
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1Select supply type. Choose Single Phase for standard residential houses or Three Phase for larger properties or light commercial setups.
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2Enter inverter AC power. Input the nominal continuous AC output power of the inverter in Kilowatts (kW).
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3Verify voltage. Ensure the supply voltage matches your connection. Standard defaults are 230 V for single phase and 400 V line-to-line for three phase.
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4Enter power factor. Input the operating power factor of the inverter (normally 1.0 for modern grid-connected inverters).
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5Click calculate. Click the "Calculate G98 Compliance" button to run the compliance engine.
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6Review G98 or G99 result. View the calculated current, maximum allowed power rating, and standard requirements.
How to Calculate G98 Compliance
G98 compliance is based on the AC export current limit of 16 A per phase. The electrical current drawn or exported is derived using active AC power formulas for single-phase and three-phase circuits. If the current is equal to or below 16 A, G98 applies. Otherwise, the system must follow G99 approval rules.
G98 Current Limit Formula
To convert inverter AC output power (kW) to output current (A), use the following standard equations:
Single Phase System:
Three Phase System:
Where:
- I = Inverter AC output current per phase (Amperes, A)
- P = Inverter maximum continuous active AC power (Kilowatts, kW)
- V = Grid supply voltage (Volts, V) — Phase-to-neutral for single phase, Line-to-line for three phase
- PF = Inverter power factor (dimensionless)
- √3 = Constant multiplier for three-phase configurations (≈ 1.73205)
Worked Example: Single Phase 3.68 kW Inverter
This is the standard microgeneration limit for UK residential properties. Let's calculate the AC current of a standard single-phase inverter:
- Inverter Power (P): 3.68 kW
- Supply Voltage (V): 230 V
- Power Factor (PF): 1.0
Result: Since the calculated current is exactly 16.00 A, this inverter is compliant with the G98 threshold. The installer can proceed with the connection and submit a notification to the local DNO within 28 days of commissioning.
Second Worked Example: Single Phase 5 kW Inverter
Let's calculate the AC current of a larger 5 kW single-phase domestic inverter:
- Inverter Power (P): 5.00 kW
- Supply Voltage (V): 230 V
- Power Factor (PF): 1.0
Result: The calculated current of 21.74 A exceeds the 16 A per phase export limit. Therefore, this installation is G99 Required, and the installer must submit a formal application to the DNO and receive prior consent before connecting the system.
G98 Inverter Chart
This reference chart outlines the expected AC export current and typical ENA connection category for single-phase UK domestic installations at various power levels. All values assume a nominal supply voltage of 230 V and a power factor (PF) of 1.0.
| Power (kW) | Voltage (V) | Current (A) | Typical Classification |
|---|---|---|---|
| 1.0 kW | 230 V | 4.35 A | G98 (Eligible) |
| 2.0 kW | 230 V | 8.70 A | G98 (Eligible) |
| 3.0 kW | 230 V | 13.04 A | G98 (Eligible) |
| 3.68 kW | 230 V | 16.00 A | G98 Limit (Eligible) |
| 4.0 kW | 230 V | 17.39 A | G99 (Prior Approval Required) |
| 5.0 kW | 230 V | 21.74 A | G99 (Prior Approval Required) |
| 6.0 kW | 230 V | 26.09 A | G99 (Prior Approval Required) |
| 10.0 kW | 230 V | 43.48 A | G99 (Prior Approval Required) |
Note: All calculations in the chart are based on unity power factor (PF = 1.0). Decreasing the power factor will increase the AC current draw for the same power level.
G98 Inverter Frequently Asked Questions
The G98 inverter limit in the UK is 16 Amperes per phase. For a standard single-phase 230V AC grid connection, this equates to a maximum inverter continuous AC output rating of 3.68 kW. If your inverter's output exceeds this current threshold, it falls under G99 connection rules instead.
Under G98, the limit is based strictly on the inverter's maximum AC output rating (3.68 kW / 16A per phase), not the solar panel capacity. You can over-size your solar panel array (e.g., installing 4 kW or 5 kW of DC solar panels) provided the inverter is limited or rated to export no more than 3.68 kW to the grid.
If a single-phase inverter exceeds the 3.68 kW (16A) threshold, you cannot connect it under the simple G98 'notify after install' route. Instead, you must apply to your local Distribution Network Operator (DNO) under Engineering Recommendation G99 and obtain approval before carrying out the installation.
No. G98 is a simplified connection process for microgenerators up to 16A per phase where you install first and notify the DNO within 28 days. G99 applies to generators larger than 16A per phase, requiring prior network studies, application fees, and formal approval before connection.
Yes, standard export limitation schemes can be accepted by DNOs. However, G98 generally applies to the raw capacity of the generating unit. For systems where export limitation is used to restrict a larger inverter to 16A, it is usually processed as a G99 Fast Track application rather than a standard G98 notification.
Yes. Battery storage inverters that can export power to the grid are treated as generators under ENA regulations. If the battery inverter output is 16A or less (and any combined generation doesn't exceed 16A), it qualifies under G98. If the combined battery and solar inverter capacity exceeds 16A, G99 rules apply.
The G98 notification must be submitted by the commissioning installer to the relevant DNO within 28 days of commissioning the system. The installer must provide technical details, certification of compliance, and a commissioning sheet to confirm the system meets ENA G98 standards.
Only the inverter's maximum AC output power (and current) matters for G98 compliance. The DC power of the solar panels (kWp) does not affect G98 eligibility, meaning you can install a larger solar array to generate more power in low-light conditions, as long as the inverter limits AC export to 16A.