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Most solar and battery systems shut down during a blackout due to mandatory anti-islanding protection. To power your home during an outage, you need backup functionality installed. Even then, only essential circuits are typically powered, and runtime depends on battery size and weather conditions.
Why Do Most Solar and Battery Systems Shut Down During a Blackout?
Many homeowners assume that if they have solar panels and a battery, their home will automatically stay powered during a blackout. Unfortunately, this is not the default behaviour of most grid-connected systems.
All grid-connected solar systems in Australia are required to have anti-islanding protection. When the grid fails, the inverter must shut down immediately. This prevents electricity from flowing back into the street’s power lines, which protects network technicians working to restore power. Because of this mandatory safety feature, even a fully charged battery cannot power your home unless the system has been specifically designed for backup operation.
What Is Blackout Protection or Backup Functionality?
To use your battery during a blackout, your system must include backup or blackout protection functionality. This requires additional configuration and often extra hardware.
When properly set up, the system automatically disconnects from the grid during an outage and creates its own independent power supply for your home. This process is sometimes referred to as forming an electrical “island.” It allows your battery and solar system to continue operating safely without feeding power back into the network.
This functionality is not always included as standard and should be clearly specified in your installation quote.
Can a Battery Power Your Entire Home?
In most cases, no. Batteries have both a limited storage capacity and a maximum power output. Running high-demand appliances such as air conditioners, electric ovens or electric hot water systems can quickly drain the battery or overload the inverter.
For this reason, most backup systems are designed to power essential circuits only. These typically include refrigeration, lighting, selected power outlets, internet equipment and device charging. By limiting supply to essential loads, a 10 kilowatt-hour battery may be able to provide power for many hours or even a full day, depending on usage.
Attempting to run the entire house during a blackout would significantly reduce runtime and may cause the system to shut down.
What Are the Limitations of Battery Backup?
Even with backup enabled, there are practical limitations. The switchover from grid to battery is not always instantaneous. When the grid fails, the system may take several seconds to detect the outage and activate backup mode. Lights may briefly flicker, and sensitive electronics could reset.
Backup duration also depends on weather conditions. If the outage occurs on a sunny day, solar panels can continue generating electricity and recharge the battery. During extended cloudy or rainy periods, the battery may eventually deplete, requiring grid restoration before power returns.
Blackout protection typically increases installation cost due to additional wiring and configuration. It is important to confirm that this feature is included if backup power is a priority for your household.
