Voltage Rise Calculator Australia
Calculate voltage rise for solar PV, generators, and regenerative loads per AS/NZS 3008
Free Voltage Rise Calculator
Enter your export parameters below to calculate voltage rise for generators, solar PV, or other power-exporting equipment based on AS/NZS 3008.
This is a simplified calculation. For detailed analysis with all installation factors and compliance checking, use our professional calculator.
Get Full Calculation ReportUnderstanding Voltage Rise in Electrical Installations
What is Voltage Rise?
When an installation exports power, current flows from the local source towards the point of supply. The cable impedance then raises the voltage at the source end above the grid voltage. Inverters and generators must stay within their overvoltage limits, so voltage rise is a design constraint in its own right.
Voltage Rise vs Voltage Drop
- Voltage Drop: current flows from the supply to a load, lowering the voltage at the load
- Voltage Rise: current flows from a source to the supply, raising the voltage at the source
- Same Formula: both use the AS/NZS 3008 mV/A/m method
- Combined Limit: AS/NZS 3000 applies the 5% limit to the sum of rise and drop
When Does Voltage Rise Occur?
Solar PV Systems
- Large commercial solar installations
- Long cable runs from inverter to the main switchboard
- Installations at the end of long distribution feeders
Generators
Standby and prime generators exporting into the installation or the grid.
Regenerative Drives
Variable speed drives that return braking energy to the supply.
Battery Storage Systems
Batteries discharging into the installation or exporting to the grid.
The Voltage Rise Formula
Single-phase: VR = (I × L × 2 × mV/A/m) / 1000Three-phase: VR = (I × L × √3 × mV/A/m) / 1000Percentage: VR% = (VR / System Voltage) × 100
AS/NZS 3008 Voltage Rise Requirements
- The combined voltage rise and drop must not exceed 5%
- Consumer mains are typically limited to 2%
- Inverters trip on overvoltage, so rise must keep the terminal voltage within their limits
- Check your DNSP connection requirements for additional limits
Cable mV/A/m Values Reference
Use these values for voltage rise calculations. Based on AS/NZS 3008.1.1 for cables enclosed in conduit at 50Hz.
| Size (mm²) | mV/A/m (0.8 PF) |
|---|---|
| 1.5 | 29 |
| 2.5 | 18 |
| 4 | 11 |
| 6 | 7.3 |
| 10 | 4.4 |
| 16 | 2.8 |
| 25 | 1.8 |
| 35 | 1.3 |
| 50 | 0.93 |
| 70 | 0.63 |
| 95 | 0.46 |
| 120 | 0.36 |
| Size (mm²) | mV/A/m (0.8 PF) |
|---|---|
| 16 | 4.6 |
| 25 | 2.9 |
| 35 | 2.1 |
| 50 | 1.55 |
| 70 | 1.1 |
| 95 | 0.78 |
| 120 | 0.61 |
| Circuit Type | Maximum Voltage Variation | Notes |
|---|---|---|
| Consumer mains | 2% | From point of supply to main switchboard |
| Submains | 5% total | Combined with consumer mains |
| Final subcircuits | 5% total | From point of supply to any outlet |
| Solar PV installations | 5% combined | Rise during export + drop during import |
Important: These limits apply to the combined voltage rise and voltage drop. Check with your local DNSP for any additional connection requirements.
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Frequently Asked Questions
Voltage Rise Questions Answered
What is voltage rise?⌄
Voltage rise is the increase in voltage at the point where power is exported into the network, for example at a solar inverter or generator. When current flows from the source towards the grid, the impedance of the cable raises the voltage at the source end above the grid voltage.
How is voltage rise different from voltage drop?⌄
They are the same physical effect in opposite directions. Voltage drop occurs when current flows from the supply to a load; voltage rise occurs when current flows from a local source back towards the supply. The same mV/A/m formula applies, and AS/NZS 3000 treats the combined rise and drop against the 5% limit.
What causes voltage rise in electrical installations?⌄
Solar PV export, generator operation, regenerative drives feeding braking energy back, and battery storage discharging all push current towards the point of supply and cause voltage rise along the cables.
What is the maximum allowable voltage rise?⌄
AS/NZS 3000 limits the combined voltage rise and drop to 5% from the point of supply. Consumer mains are typically limited to 2%. Inverters also have overvoltage trip limits, and DNSPs may impose tighter limits at the connection point.
How do I calculate voltage rise?⌄
Voltage rise = (I × L × K × mV/A/m) / 1000, where I is the export current, L is the cable length, K is 2 for single-phase or √3 for three-phase, and mV/A/m comes from AS/NZS 3008. Divide by system voltage for the percentage.
When should I consider voltage rise in my design?⌄
Any time the installation exports power: large commercial solar installations, long cable runs from the inverter to the main switchboard, installations at the end of long distribution feeders, standby generators and battery storage systems.
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