OverSizing a Solar inverter
Oversizing an inverter means connecting more panel power than the inverter's rating.e.g. 6.6kW of panels on a 5kW inverter
or 13.2kW of panels on a 10kW inverter
If you stay within 133.33% oversizing then you get paid STCs, the still generous Government subsidy on panels.
The rationale for this allowed oversizing is that solar conditions are not always ideal.
Early morning, late afternoon, or entire seasons like Winter, if you only had 5kW of panels on a 5kW inverter
your inverter wouldn't be able to pull down enough power from the panels to hit its 5kW limit.
When you connect a battery to your solar inverter then you can add even more panels.
Huawei, Growatt, Sungrow (single phase), SolarEdge allow at least 200% oversizing with a battery.
That means, at least 10kW of panels connected to a 5kW inverter, or 12kW to a 6kW inverter.
One caveat though...
the panel input voltage must stay below 600V DC, and voltage and current must conform to manufacturer limits as well.
In the real world, this impacts which panels you can use as they have different voltage and current characteristics.
e.g. In Perth you could just have 2 x strings of 12 x 415 JinKo 415W 'N' types, so 9.96kW
or you could have 2 strings of 12 x 475W JinKo 'N' types, so 12.35kW
Different panels, different specs, different oversizing possible.
The STC 'panel subsidy' will also be paid on these additional panels as long as all other regulatory conditions are met.
Fronius allow 150% oversizing with their GEN24Plus hybrids, as do Sungrow with their three phase hybrid models, which,
whilst not as good as with other brands, is still better than nothing.
The graph from one of our clients installations below clearly shows what goes on with this extra oversizing and a battery.
The client has a 5kW single phase inverter, and 8kW of panels and a 15kWh battery.
The green line is the solar power production which peaked at 6.5kW (remember this is a 5kW inverter).
The blue line is the battery being charged.
At 11.50am, the battery is fully re-charged and the solar production drops off.
Once the battery is full, the extra panels help keep the output as close to the 5kW inverter max, for as long as possible.
We've done many installations of hybrid inverters with oversizing up to, and beyond 200%, and always been paid the STCs.
This video about batteries shows four of these installations examples (Huawei, Fronius, Sungrow Goodwe hybrids with batteries)
If you want a quote for solar in Perth (South as far as Mandurah, North to Yanchep/Chittering) call us on...
or email
Written by Andrew MacKeith, Solar4Ever Service Manager since 2011.
Most recent update December 2021
