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.
Why arrays are oversized
Panels rarely make their rated output: heat, angle and the time of day all take some off. A slightly larger array keeps the inverter near full output for more of the day, and fills the shoulders of the morning and evening, for the cost of a little clipping at midday.
Solar Accreditation Australia, whose requirements accredited installers work to on systems that claim STCs, caps how far it can go: the inverter's AC output may not be less than 75% of the array's peak power. That lets the panels reach a third more than the inverter: 133%.
Largest array = inverter capacity ÷ 0.75
Worked example
Panels24 × 550 W = 13.2 kW
Inverter10 kW
13.2 ÷ 10 = 132%Within the limit of 13.33 kW
Questions installers ask
Is this the same as the network's limit?
No. The distributor's limits on inverter size and export are separate, and a system has to meet both.
What happens over the limit?
The design does not meet the accreditation requirements, which puts its STCs at risk. Use a larger inverter or fewer panels.
Does a battery change it?
With a connected battery the 75% ratio can be exceeded, as long as the array stays within the inverter maker's maximum array size (clause 4.2).