TL;DR: Solar alone does not keep your lights on in a blackout. Your inverter shuts down the moment the grid drops, by law. Getting backup power means a battery, a hybrid inverter, and a separately wired essential-loads circuit. Budget $10,000 to $18,000 installed for a 10-14kWh system before rebates.
Why Your Solar System Shuts Down in a Blackout
This surprises almost every new solar owner, usually during their first outage.
Grid-connected inverters are required to disconnect when the grid fails. It is called anti-islanding, and the reason is that a line worker repairing a fault has to be able to trust that a dead line is dead. If thousands of rooftop systems kept pushing power into the network, it would not be.
So on a sunny afternoon with your array producing 5kW, an outage leaves you in the dark alongside neighbours who have no solar at all.
What Changes With a Battery
A battery system with backup capability does the same disconnect, then does something extra: it opens a physical switch that isolates your house from the network, and starts running your own circuits from stored energy.
Once that isolation is confirmed, your solar panels are allowed to restart, because they are now feeding an island that is provably disconnected from the grid. The battery charges, the house runs, and nothing reaches the street.
The switchover completes in tens of milliseconds. Lights may flicker; computers and fridges generally do not notice.
The Hybrid Inverter and the Essential Loads Circuit
Two pieces of hardware make this work.
A hybrid inverter manages solar, battery and grid together, detects the outage, and controls the transition. A standard grid-tied inverter cannot do this, which is why adding a battery to an older system sometimes means replacing the inverter as well.
An essential loads panel is a second, smaller switchboard holding the circuits you want backed up. During normal operation it is fed from the grid like everything else. During an outage it is the only thing the battery powers.
Backing up the whole house instead needs a much larger inverter and battery, because an air conditioner or electric oven starting up draws more than most residential batteries can deliver. What goes on the essential circuit is decided before installation, and moving one afterwards means an electrician back at the board.
What It Will Actually Run
A typical 10kWh to 14kWh battery will carry a well-chosen essential circuit for 12 to 24 hours, and longer if the sun comes up and starts recharging it.
What normally goes on that circuit:
- Fridge and freezer
- Several lighting circuits, not all of them
- Internet router and modem
- Power points for phone charging and laptops
- Medical equipment such as a CPAP machine
- Gas hot water and heating controls, which draw almost nothing but stop working without power
What normally does not:
- Ducted air conditioning
- Electric oven and cooktop
- Electric hot water
- Pool pump
- EV charger
Those are excluded on power draw, not importance. An electric oven pulls more on its own than most home batteries can supply, and a ducted system empties a 10 kWh battery in an evening.
Sizing It Against Your Own Loads
Work from actual consumption rather than a rule of thumb.
A modern fridge uses roughly 1-2 kWh per day. A router and a handful of LED lights come to under 0.5 kWh over an evening. Add up everything you want on the circuit and you have a daily essential load, which for most households lands somewhere between 3 and 6 kWh.
At 5 kWh a day of essential load, a 10 kWh usable battery gives you two days with no sun at all. With any daytime generation it recharges and the backup runs indefinitely, which is the situation in most Australian outages, since these are typically storm-related and daylight is not the problem.
Ask your installer for two numbers: usable capacity, which is lower than nameplate, and continuous backup output in kW, which decides whether the circuit trips when the fridge compressor and the microwave start together.
Ask About Black Start
One question most quotes do not address: can the system restart itself if the battery fully discharges during a long outage?
Some restart from solar alone. Others need a grid connection to wake up, which is the one thing you do not have. Where outages run for days, that matters more than an extra kilowatt-hour.
What It Costs
Expect $10,000 to $18,000 installed for a 10-14kWh system with backup capability. A quality 10kWh battery in Sydney or Melbourne typically lands between $12,000 and $15,000 fitted.
That covers the battery, the hybrid inverter and the labour, including wiring the essential loads panel. Adding backup to an existing system costs more where the inverter has to be replaced with a hybrid unit, common on installations more than about five years old. Battery brand, switchboard condition and cable runs move the rest.
Rebates and Payback
The federal Cheaper Home Batteries discount cuts roughly 30% off eligible installed battery costs through the Small-scale Renewable Energy Scheme, applied by your installer at the point of sale rather than claimed back later.
State programs stack on top in some cases. Victoria's Solar Homes Program has offered rebates up to $1,400 alongside interest-free loans, and South Australia has run its own scheme. These change often and close when funding caps are hit, so check current terms.
On bill savings alone, payback for battery storage typically runs 7 to 12 years, shorter where you have a large evening load and a poor feed-in tariff.
That calculation misses the point for most people buying backup. If you work from home, keep medication refrigerated, or live at the end of a rural feeder that drops several times a winter, the value is in not losing those days, and that never appears in a payback spreadsheet.
Key Takeaways
- Solar without a battery shuts down in a blackout. Anti-islanding is a safety requirement, not a fault.
- Backup needs three things: a battery, a hybrid inverter, and an essential loads panel wired at installation.
- A 10-14kWh battery runs a sensible essential circuit for 12 to 24 hours, longer with daytime generation.
- Exclude high-draw loads such as ducted air conditioning, electric ovens and EV chargers from the backup circuit.
- Budget $10,000 to $18,000 installed before rebates, and ask whether the system can black start from solar alone.
Read More
For a complete overview, check out our master guide: Read the Full Guide Here.
