Export limits and the sun tax: what solar owners need to know

Solar export limits and the sun tax: what they are, why they exist, how they affect your solar return, and what you can do about them - covering fixed and dynamic export limits, which states are affected, and why a battery changes the equation.

Key findings

• Most networks cap solar exports at 5kW per phase for single-phase homes. A 10kW system will be curtailed for hours on sunny days without storage.
• The "sun tax" isn't a tax - it's a network service fee some networks apply to exports during peak solar hours, and only above a free daily allowance.
• South Australia was the first state to roll out flexible exports at scale. New systems installed since July 2023 must be flexible-export capable, which allows up to 10kW per phase depending on network conditions. The fixed alternative is 1.5kW or 0kW depending on your area.
• A battery is the most effective response - captures otherwise-curtailed surplus and converts it into evening savings.
• Export limits don't affect how much your panels generate. Only how much you can send to the grid. Your household loads are always served first.

Why export limits exist

Australia has the highest rooftop solar penetration in the world. In some suburbs, more than half of homes have solar. On a sunny weekday afternoon the volume of electricity flowing back into the grid can exceed what the local network was designed to handle. Export limits prevent voltage spikes that could damage appliances and cause outages - they're an engineering constraint, not a commercial one.

Fixed vs dynamic export limits

Fixed export limit

A hard cap regardless of network conditions. Most common is 5kW per phase. In South Australia the fixed option is 1.5kW or 0kW depending on your area, which is why almost nobody chooses it there. When you hit the cap the inverter throttles back and the surplus is wasted.

Dynamic (flexible) export

The network communicates with your inverter in real time. When the grid has spare capacity your limit rises, potentially to 10kW. When congested at midday, it drops. Over a year, most households export more total energy under dynamic limits than under a 5kW fixed cap.

South Australia went first on this and it is now the default. More than 86% of eligible SA customers are on flexible exports. One thing to know: it depends on your inverter holding an internet connection. If that drops out, your export falls back to the fixed limit until it comes back. Worth setting up properly at installation rather than discovering it later.

What the sun tax actually is

Export charges some networks apply during peak generation hours (typically 10am to 3pm), and only above a free daily allowance. In practice most households see a very small annual impact - often $10 to $20/year. The more meaningful response is to stop exporting at midday by using a battery, shifting loads to solar hours, or charging an EV during peak generation.