There are five ways to ask this question and one answer: the certificate count follows the panels. The kW figure in the STC formula is the rated capacity of the solar panels installed, taken from the approved product list, multiplied by the zone rating and the deeming period. The inverter does not set it. The inverter does, however, limit how many panels you can put on a system and still be eligible.
How the system kW rating is determined
Each panel model on the Clean Energy Council (CEC) approved list has a rated output in watts at standard test conditions. Add them up. Thirty panels at 440 W is 13.2 kW. That 13.2 is the figure that goes into the STC calculation, so a 13.2 kW zone 3 system creates 91 STCs in 2026 (13.2 x 1.382 x 5, rounded down). See STCs by system size.
Panel kW versus inverter kW
The inverter rating is its continuous AC output. It matters because:
- It caps what you export or run at any moment.
- It sets the maximum panel capacity under the oversizing guidelines.
- It may be limited by the distributor, with export limits that vary by state.
It does not add STCs. Selling a customer a bigger inverter for “more rebate” is wrong, and the other way round, a smaller inverter with the same panels earns the same certificates.
The 133 per cent rule
For a standard grid-connected system, the panel array can be up to 133 per cent of the inverter’s AC rating under the CEC guidelines used to support STC eligibility. So:
| Inverter | Maximum panels |
|---|---|
| 5 kW | 6.65 kW |
| 6 kW | 7.98 kW |
| 8 kW | 10.64 kW |
| 10 kW | 13.3 kW |
That is why 6.6 kW of panels on a 5 kW inverter is standard. Systems with batteries and multiple inverters can have extra conditions, so check the current CEC design guideline for your configuration.
What happens with an oversized array
If the DC capacity exceeds the allowed ratio, the installation may not meet the guideline and the STC claim can fail or be reversed on audit. The intent of the rule is to stop people claiming certificates on panels that will never reach their rated output through a small inverter. The practical answer is to design within the ratio or accept that the job may not generate STCs.
What this means for installers
Record the panel model, count and serial numbers, and keep the inverter data sheet in the job file. Auditors compare the rated panel kW to the inverter and to the photos. See how STC audits work and photo requirements. If you are not sure what a system will create before you quote, the STC calculator uses the panel kW and postcode.
If a customer asks why the “kW” on a quote differs from the inverter label, this is the reason: the quote uses panels, the label shows the inverter. For rebate dollars see STC rebate value by size, and for how a trader checks claims see how it works.