How does export limit for solar work?
Solar export limits are in place to protect grid infrastructure and to prevent over voltage. When too much power is exported to the grid the voltage increases and causes your systems inverter to ramp down and protect itself and in turn reduce the voltage.
All grid connected solar systems must be approved by the network and all export is subject to approval. Typically in Australia 5kW per phase can be exported to the grid. So your average single phase property can export 5kW per hour back to the grid. Now if you were exporting 5kW per hour for 10 hours this would be 50kW per day you were exporting, still quite a bit. If you have dual phase you can export double this capacity (10kW) and if you have three phase you can triple this capacity (15kW).
For residential properties the maximum solar inverter capacity that can be installed is 10kW per phase. You can then oversize this by 33% with panel capacity and still claim the STC rebate. Some inverter will allow 50% panel oversizing but you cannot claim the STC rebate for the additional 17% capacity.
Standard Solar Capacity Allowance for Grid Approval
You might be wondering, why would install a larger inverter than 5kW if thats the maximum export at my single phase property? Well there are two main reasons.
Firstly, the extra capacity goes towards your daytime load. As your daytime consumption increases the systems production ramps up to meet that load whilst feeding the maximum allowed back to the grid. Therefore you can potentially cover all of your daytime load whilst still exporting the maximum allowance back to the grid. See this 13.3kW with 10kW inverter capacity below and see the inverter increases production to meet the load plus 5kW export:
Secondly, a 5kW inverter, for example, rarely produces 5kW even with 6.6kW of Solar PV installed. Even on a perfect sunny day the system takes a while to ramp up to maximum performance. You also have cloud cover, shorter winter days and the orientation of the panels to consider and the fact that a larger system will always produce more at these times. Below shows a 6.6kW system on the left and on the right it shows the extra production potential of a 13.3kW system.
6.6kW Monitoring (Clear Day)
Same 6.6kW with extra production possible with a 13.3kW system
Solar in Australia is such a good investment assisted by a Federal Government rebate as well as getting paid for exporting power to the grid (yes, for less than we pay for power but for much more than it costs you to produce with your system) so by maximising your system capacity you are increasing your solar yield, savings and profits from your investment.
If you are a very low daytime user and you opt for the largest system possible there will be some clipping and some reduction in potential yield but you might be surprised with how much more you can still save and benefit. In the 13.3kW example below we see the inverter clipping due to the 5kW export limit but note the daily production in the top right its still much higher than we see from a 6.6kW system (above).
Clipping on a 13.3kW System – 5kW Export limit
Extra production that would have been produced without the export limit of 5kW
Typical Export limit loss over the year (examples)
- 5kW inverter + 6.6kW of solar panels (no export limiting): 0% loss
- 6kW inverter + 8kW of solar panels: 3% loss
- 7kW inverter + 9kW of solar panels: 7% loss
- 8kW inverter + 10kW of solar panels: 10% loss
- 10kW Inverter + 13kW of solar panels: 13% loss
For commercial 3 phase installations we can apply for full export. A network fee may be applicable but this can be discussed and added to the quotation initially upon request.