Solar Export Limiting is a control mechanism used in solar power systems where the amount of excess solar power that can be sent back to the grid is capped at a certain level. This practice has become increasingly common as a means to have larger solar PV systems approved by the grid network operator.
For instance, in WA, Western Power now allows 3-phase homeowners to install up to 15kW of inverter capacity on the condition that a 1.5kW ‘Export Limit’ must be set.
How Does Export Limiting Work?
When your solar panels are producing more electricity than your home needs, the excess would traditionally go to the grid. However, with an export limit set, your system’s output adjusts in real-time to prevent too much excess solar power fed to the grid.
Graphical Representation
Normally, on a sunny day, a solar PV system will generate solar power in proportion to irradiance. The result; a nice smooth bell curve. For example…
However, if your system is Export Limited, you’ll notice that the solar PV graph fluctuates up & down in parallel with the home Load. For example, below is a system dynamically adjusting solar power production to achieve a 1.5kW Export Limit.
As you can see, when household electricity usage (Load) increases, solar PV production can also increase to meet that demand. When electricity usage decreases, so does solar power production. All the while, no more than 1.5kW of excess solar power is exported to the grid.
Battery integration
If you have a battery installed, export limiting is delayed until the battery is fully charged. Excess solar power is first directed to charge the battery rather than exported to the grid. Only after the battery reaches full capacity (100% State-of-Charge) does the export limiting kick in.
Why Implement Solar Export Limiting?
From Western Power perspective, the primary reason for imposing export limits is to maintain grid stability. Too much solar power being fed into the grid at once can destabilize the grid voltage and frequency, especially in regions with high solar penetration.
Advantages of Export Limiting
From a customer’s perspective, export limiting has two main benefits:
1/ Approval for a Larger system
Gone are the days where 6.6kW is considered a large solar system. With the price of solar as low as it’s ever been, 10kW – 20kW systems are now the norm for 3-phase properties.
These larger systems are more future-proof and better suited for:
– Running the air-conditioner freely
– Charging a future battery
– Charging a future electric vehicle(s)
– Switching from gas hot water to an electric Heat Pump
– Switching from gas cooking to electric induction
– Pool heating
To gain Western Power approval for an inverter larger than 5kW, the only requirement is a 1.5kW Export Limit must be set.
2/ AVOID Emergency Solar Management / Remote Shutdowns
At times when a neighbourhood has too much solar power being exported to the grid, Synergy has the ability to remotely switch OFF solar systems. They call this “Emergency Solar Management” (ESM).
During an ESM event, or periodic ESM Compliance Testing, those solar systems affected are non-operational, which means homeowners are forced to buy grid power from Synergy instead. Not very fair!
Fortunately, there is a way to Opt Out of ESM events. With a permanent 1.5kW export limit set, your system is not required to comply with ESM rules. Instead, your system will remain ON and continue to provide power to your home, protecting your energy independence and savings.
NB. To opt out of ESM requirements, you must also opt out of Synergy’s ‘Distributed Energy Buyback Scheme’ (DEBS) i.e. the credit paid for excess solar power exported to the grid. At the time of writing, the DEBS feed-in tariff is only 2-cents/kWh before 3pm, and 10-cents/kWh after 3pm. Not very much.
CONCLUSION
Rest assured, export limiting doesn’t mean less solar power for personal use or battery charging. In fact, the opposite is true. Export limiting allows you to have a larger, more future-proof system, while also preventing Synergy from remotely shutting down your system during ESM events.
Thinking Solar? Think Positive! The team at Positive Energy Solutions are industry experts here to provide advice you can trust. Get in touch for a quote today. Our approach is honest, informative, no pressure.
