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How this is calculated#

The tool works out the voltage rise on the cable between an inverter and its point of supply. It uses the cable data of AS/NZS 3008.1.2:2017. The Australian choice reads AS/NZS 3008.1.1:2025 and the superseded 2017 edition.

1. Inverter current. The tool divides the inverter power by the voltage and the power factor. On three phases, it also divides by the square root of three.
2. Resistance and reactance. It reads the conductor resistance from Tables 34 and 35. It reads the reactance from Table 30. It uses the value for your size, material and insulation.
3. Millivolts per ampere metre. It combines both values with the power factor. This is the method of Cl 4.5.
4. Voltage rise. It multiplies the millivolts per ampere metre by the current and the run length. It gives the result in volts and as a percentage of the supply voltage.
5. Maximum length. It finds the run length at which the rise equals your limit.

The limit is an input. AS/NZS 3000:2018 Cl 3.6.2 Note 3 refers the rise limit to AS/NZS 4777.1. Check the current edition for the value that applies to your site.

Worked example#

• 5 kW inverter on 30 m of 10 mm² copper. The supply is single‑phase at 230 V with a power factor of 1. The inverter current is 21.74 A. The voltage rise is 2.91 V, or 1.26 %. That is within a limit of 2 %. The longest run at that limit is 47.44 m.

Limits#

The limit of 2 % is a default you can change. It is not a value read from a standard. The tool does not check the inverter voltage settings or the rules of the network operator.

The reactance is the Table 30 value for a multicore cable. A single‑core run reads a higher reactance for its formation. The tool does not size the cable for current. Use the cable size calculator for that.

See also: Solar inverter voltage rise at 5 kW, Voltage rise on a long rural PV run and the PV string tool.