Solar Battery Backup in a Blackout: What Actually Keeps Running
Solar panels on their own switch off in a blackout, even on a sunny day. To keep power running, you need a solar battery backup system that is designed and wired to isolate your home from the grid. Most backup set-ups run selected essential circuits, such as the fridge and lights, rather than the whole house.
Here is why that happens, and what to check before you count on a battery during an outage.
Why your solar panels switch off when the grid goes down
A standard grid-connected solar system shuts down during a power outage, with or without a battery. It is a safety feature, not a fault. If panels kept sending electricity into the network, that power could reach lines that crews are repairing. Solar Victoria and the Queensland Government's battery buyers guide both explain that systems switch off to protect people working on nearby lines.
So your solar panel system can be generating at midday and still leave your home without power. New to solar? Start with how solar panels work — see our guide on how solar panels work.
What blackout protection really means
Blackout protection, or backup power, lets a battery system disconnect your home from the grid during an outage and keep supplying stored energy to the house, not the street.
Not every blackout protection battery set-up is the same. Some batteries include backup, others can add it at extra cost, and some do not offer it at all. Whether a solar battery with blackout protection works in your home depends on the battery, the inverter and the wiring. Our solar battery systems page covers the options.
Built-in backup or add-on backup
Some hybrid (multimode) inverters have backup built in. Others need extra equipment, and Solar Victoria notes home wiring may need adapting. Ask which type you are getting and whether it costs extra.
Can your panels recharge the battery during an outage?
It depends on the design. Solar Victoria says multimode systems can generally run standalone, but this varies by product. Ask whether the panels will keep charging the battery in a daytime blackout, as that decides how long backup lasts in a multi-day outage.
Essential circuits or whole-home backup?
Solar and battery backup comes in two main types. The Queensland Government notes that whole-of-home backup drains the battery faster, while essential-load backup makes stored energy last longer.
| Essential-load backup | Whole-of-home backup | |
|---|---|---|
| What runs | Selected circuits, such as the fridge, lights and some power points | Most or all of the home's circuits |
| Battery use | Lasts longer, as fewer appliances draw power | Drains faster, as more appliances run at once |
| Suits | Households wanting the basics covered | Households wanting near-normal use in short outages |
Check before you buy
- Exactly which circuits are included
- Whether the inverter can run your larger appliances
How to plan what you'll run during an outage
How long backup lasts depends on the stored energy available, what your appliances use, and whether solar can recharge the battery. No single runtime figure fits every home, so before you speak to an installer:
- List what you would need running, such as the fridge, lights, internet modem and phone chargers.
- Note large loads like ducted air conditioning or electric cooktops and decide whether they need backup.
- Ask how much charge will be kept in reserve for outages, and which circuit each appliance sits on.
If your system can recharge from solar in an outage, a larger array such as a 10kW solar system or 13kW solar system refills the battery faster on a sunny day.
Does the battery rebate require blackout protection?
No. Blackout protection is not listed as a requirement under the federal Cheaper Home Batteries Program.
To qualify, the battery and inverter must be able to join a virtual power plant (VPP), the battery must be on the Clean Energy Council's approved list and comply, and a Solar Accreditation Australia installer with battery endorsement must install it. A battery can therefore qualify without powering your home in a blackout, so confirm backup separately. See our solar rebate page for current incentives.
Joining a VPP? Solar Victoria notes VPP batteries are not customised for backup, and the Queensland Government lists less reserve capacity for outages as a possible drawback.
Safety points before you rely on backup
- Life support equipment. Solar Victoria advises seeking specialist advice, as home batteries are typically not suitable as the primary power source for medical equipment. Make sure you are registered as a life support customer with your electricity retailer.
- Storm damage. A damaged system may be unsafe. The Queensland Government advises shutting it down using its procedure, only if safe, then contacting your installer or 3P Solar support.
- Battery location. Batteries cannot go in habitable rooms. The Queensland Government battery safety guide lists other placement rules.
Questions to ask your installer
- Does this battery and inverter provide blackout protection, and is it in the quote?
- Which circuits will be backed up?
- Will the panels recharge the battery during a blackout?
- Is the battery CEC-listed, and is the installer SAA-accredited?
Getting answers in writing makes it easier to compare solar and battery packages like for like.
Key takeaways
- Grid-connected solar switches off in a blackout to protect line workers.
- Backup needs a battery and inverter set up for it. Not all batteries offer it.
- Essential-load backup lasts longer than whole-of-home backup.
- The Cheaper Home Batteries Program does not list backup as a requirement.
Frequently Asked Questions
Not on their own. Grid-connected solar switches off during an outage to protect line workers. It needs a battery system set up for backup to keep your home powered.
No. Some include it, some can add it at extra cost, and some do not provide backup at all. Check the exact battery and inverter combination.
When the grid fails, a backup-capable system isolates your home and supplies stored energy to the backed-up circuits. No power flows back into the network.
It should not be the main power source. Solaareer Victoria advises getting specialist advice, as home batteries are typically not suitable as the primary supply for medical equipment.
Keep your essentials running
Adding a battery and want the basics covered in an outage? Speak with a 3P Solar expert about your current home solar system, what you want backed up and which battery set-up suits your home.
