What Happens to Excess Solar Energy When Your Battery Is Full?

Quick answer: Once your battery is full, your hybrid inverter stops charging it and sends excess solar energy to your home’s appliances first, then to the electricity grid, where your retailer may pay a feed-in tariff. If your network limits exports, the inverter turns down your panels and the surplus is simply not produced.

Most guides that answer “how do solar batteries work” stop at charging and discharging. The practical question comes around midday, when the battery hits 100% and the panels keep producing. Where that power goes depends on your inverter, your network connection and whether you’re on or off the grid.

How Do Solar Batteries Work When They Reach 100%?

A home battery is controlled by its battery management system and a hybrid inverter. Once a solar battery full charge is reached, the battery management system tells the inverter to stop charging, which protects the cells from overcharging.

From that point, your solar output follows a set order:

• Power the appliances running in your home.

• Charge the battery (skipped once it’s full).

• Export what’s left to the grid, if your connection allows it.

• Reduce panel output if exports are capped.

Using as much of your own power on site as possible is called solar self-consumption. Every kilowatt-hour you use at home is one you don’t buy from your retailer.

Exporting to the Grid and Earning a Feed-in Tariff

For grid-connected homes, surplus power flows through the meter to the local network once the battery is full. Your retailer may credit these exports as a feed-in tariff on your bill.

Rates differ between plans. The South Australian Government notes that retailers set their own feed-in tariff rates, while in regional Queensland the Queensland Competition Authority sets a regulated rate each year. See how feed-in tariffs work and net metering for the detail.

What Happens When Exports Are Blocked? Solar Curtailment Explained

Your local network may set a solar export limit, which caps how much power your system can push to the grid at once. ARENA reports that in areas with high rooftop solar uptake, networks have imposed zero or near-zero export limits on new systems.

When your battery is full and you’ve reached that limit, the inverter lowers your panels’ output. This is solar curtailment. Your panels aren’t damaged, and the extra electricity is never generated in the first place.

Flexible export limits reduce how often this happens, because the limit moves with network conditions instead of staying fixed. In South Australia, exporting solar systems installed from 1 July 2023 must be compatible with flexible exports under SA Government rules, according to SA Power Networks (status: active). Read more about solar and batteries in South Australia.

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