A tool does one sum. Solar Base does the whole job.
The STC count, the NMI, the meter alteration and the invoice, worked off one job record, with the last step left to you.
What voltage rise is
Voltage drop and voltage rise are the same sum run the other way. When an inverter exports, current flows out from it to the grid, and the voltage at its terminals sits above the voltage at the point of supply by the drop across the cable in between.
When the grid is already running high, that extra rise is what pushes an inverter into its volt-watt response or trips it on overvoltage, which the customer sees as a system that stops exporting on sunny afternoons. Keeping the rise small is cheaper than chasing the fault later.
Rise = 2 × L × I × ρ ÷ A (single phase)
Worked example
Inverter5 kW single phase, 21.7 A
Consumer mains15 m of 16 mm²: 0.85 V
Inverter run22 m of 4 mm²: 4.99 V
Total 5.84 V of 230 V = 2.54%, over 2%A 6 mm² inverter run brings it to 1.82%
Questions installers ask
Where does the run start?
At the point of supply, so the consumer mains count as well as the cable from the switchboard to the inverter.
Why a 75 °C conductor temperature?
Copper's resistance rises with temperature, and a loaded cable runs warm. Working at 75 °C gives a rise you will not exceed on a hot day at full output.
Does this replace the AS/NZS 3008 tables?
No. For the cable sizes on a house the resistive estimate sits close to the tables, but the tables include reactance and are what your design record should cite.
What about three phase?
Pick three phase and enter the current per phase. For a balanced load the rise uses √3 in place of 2 and is taken against 400 V.
Do networks ask for less than 2%?
Some do on part of the run. Jemena's guideline asks for no more than 1% between the main switch and the inverter. Check your network's connection rules.