A grid-connected PV system has three parts that matter to the wiring. The array on the roof, the inverter on the wall, and the cable from the inverter to the switchboard. Each part sits under a different rule set.
The DC side and the AC side
The array and its strings are direct current. Module voltages add along a string, and a string can reach several hundred volts in sunlight. AS/NZS 5033:2021 covers the array side. This page names the standard and points you to it. No string limit, no isolator rule and no DC cable value on this site is quoted from it, so read the clause that applies before you rely on a figure.
The inverter converts the array output to alternating current at the installation voltage. From the inverter terminals onward the circuit is ordinary AC wiring. AS/NZS 3000:2018 Cl 7.3 covers generation connected to an installation. The inverter cable takes the same checks as any other cable: current-carrying capacity, then voltage, then fault performance.
AS/NZS 4777.1 covers the connection of the inverter to the grid. Cl 3.3.3 of the 2016 edition sets the voltage rise limit at 2 % of the nominal voltage at the point of supply, calculated at the rated current of the inverter energy system. That is the limit the voltage rise tool applies.
Why rise, not drop
A load draws current from the switchboard. Voltage falls along the cable toward the load. An inverter pushes current toward the switchboard. Voltage rises along the cable toward the inverter. The arithmetic is the same arithmetic. Only the direction changes.
Rise matters because the inverter watches the voltage at its own terminals. The supply is already somewhere in its normal band. The rise adds to it. If the sum reaches the inverter trip point, the inverter reduces output or disconnects. The array is fine and the export stops anyway.
AS/NZS 3000:2018 Cl 3.6.2 Note 3 refers voltage rise to AS/NZS 4777.1. The voltage rise tool uses 2 % as its own default. That figure is the tool's assumption. Read the current edition of AS/NZS 4777.1 for the limit and the clause that apply to a real job.
A worked inverter cable
Take a 5 kW single‑phase inverter at 230 V, power factor 1. The run to the switchboard is 40 m on 10 mm² copper with PVC insulation. The rise limit is 2 %.
The tool works the output current first: 21.74 A. It reads the conductor resistance as 2.23 Ω/km and combines it at the stated power factor to get 4.46 mV/A·m. Over 40 m at 21.74 A that gives a rise of 3.88 V, which is 1.69 % of 230 V.
The number that earns its keep is the maximum length: 47.44 m. The cable passes at 40 m with about 7 m to spare. The tool still raises a warning, because the result sits close to the limit. A route change on site can use that margin up.
Two moves recover margin. Increase the conductor size, which lowers the millivolt figure. Shorten the route, which is often possible when the inverter can sit nearer the switchboard.
Open the voltage rise calculator with these inputs.
The point of supply and the demand side
The inverter cable ends at a point in the installation, not at the meter. A subboard connection adds the subboard cable to the rise path. Work the whole path from the inverter to the point of supply, not the last leg alone.
Batteries add a second source and a second set of cables. Use the battery tool for the bank current and the cable size tool for the conductor.
For demand assessment, AS/NZS 3000:2018 Table C1 group J(iv) is the group that covers this kind of equipment. The max demand tool applies the group rule. A PV system does not reduce the maximum demand. The demand rule sizes the mains for the load.
What this page does not answer
Electricity (Safety) Regulations 2010 reg 6A applies to work of this kind. This page cites the regulation number only. It does not say who may carry out the work or how the work is certified. Read the current reprint of the Regulations.
Anti-islanding, network approval and export limits sit outside the AmpSize engine. The tools cover the cable, the current and the rise.
A habit worth keeping
Size the inverter cable on rise first, then confirm capacity. Load cables usually fail on capacity and pass on voltage. Inverter cables are the other way around. The current is modest and the run is long, so the voltage check is the one that picks the size.
This page is a design aid. Verify every value against the current edition of the standard.