Will your battery keep the lights on in a blackout?
The honest answer surprises most people: a home battery does NOT automatically back up your home in an outage. Backup has to be specifically designed and installed — and even then, what it can run at once is limited. Here's exactly how it works, before you buy.
Reviewed by Josh, Mission Green Energy Team · Updated July 2026
Does a battery back up
your home automatically?
No — and this is the single biggest misconception we see. Most home batteries provide no backup at all in a grid outage unless backup was specifically designed and installed. A battery is not the same thing as blackout protection.
Here's what catches people out. A standard grid-connected battery is required by the rules to shut down when the grid goes down. It's a safety mechanism — called anti-islanding — that stops your system from pushing power into the network and endangering the line workers trying to fix the fault. So without extra hardware, your battery sits there full of energy and does nothing for your home during a blackout, exactly like a grid-tied solar system without a battery.
To get backup, two things have to be built in at installation: a backup gateway (a changeover device that safely islands your home from the grid) and a nominated essential-circuits subboard (the specific circuits that stay live). Neither is automatic and neither is standard on every install. If you assumed "battery = lights stay on", you're in good company — but it's a costly assumption to discover during your first outage.
The good news: backup is absolutely available if you want it, and this page walks through exactly what to ask for. If bill savings are your main goal and you're relaxed about the odd blackout, a standard install is cheaper and still does the important job of storing and using your own solar. Either way, decide it deliberately. See how backup fits the bigger picture in our honest guide to whether a home battery is worth it.
Why does a battery switch off
the moment the grid fails?
It's not a fault — it's a safety rule. Without a backup gateway, your battery is legally required to disconnect when the grid goes down, so it can't power your home even though it's full.
Grid-connected solar and battery systems have to protect the people working on the network. If a battery kept feeding power into the wires during an outage, it could electrify lines that a repair crew believes are dead. So the standard behaviour — anti-islanding — is for the inverter to sense the grid has failed and shut its output down within moments.
A backup gateway is the device that changes this. It physically disconnects (or "islands") your home from the grid, so your battery can safely run your nominated circuits without any risk of back-feeding the network. That's the whole reason backup needs deliberate design: it isn't a setting you flick on, it's hardware that has to be specced, supplied and wired in by a licensed electrician. A properly installed backup setup keeps your essentials alive and keeps line workers safe — the two aren't in conflict once the gateway is there.
What has to be installed
for a battery to give backup?
Three ingredients turn a savings battery into a backup battery. Miss any one and you get no power in an outage — so it pays to know what you're actually paying for.
A backup gateway
The changeover or automatic transfer device that safely islands your home from the grid so the battery can run without back-feeding the network. No gateway, no backup — this is the piece that's most often left out of a savings-focused quote.
An essential-circuits subboard
A nominated set of circuits — typically lights, the fridge, wi-fi and a few power points — wired to stay live in an outage. You choose what's on it. Whole-home backup is possible but needs deliberate design and usually more capacity.
A battery & inverter rated for it
Not every battery or inverter supports backup, and each has a continuous power limit. The system has to be specced to deliver enough power for your chosen essential circuits — which is why the honest conversation happens before you buy, not after.
How much of your house
can it actually run?
Even with backup fitted, a single battery runs your essentials — not your whole home with everything on. Continuous backup power is commonly around 3 to 5 kW, and that number sets what you can run at once.
This is the second half of the misconception. People who do have backup sometimes expect the whole house to carry on as normal — and it usually can't. A single home battery typically delivers around 3 to 5 kW of continuous backup power (the exact figure depends on the unit, so check your battery's specifications or the manufacturer's page). That comfortably runs the essentials: lights, the fridge, wi-fi, phone and laptop charging, and some power points.
What it generally won't run — certainly not all at the same time — is the heavy stuff: ducted air conditioning, an electric oven, an instantaneous electric hot-water unit, a pool pump, or an EV charger. Try to draw more than the battery can supply and the backup can overload and trip. Whole-home backup that keeps the big loads going is achievable, but it needs deliberate design and often more than one battery, which costs more.
So the honest questions to put to your installer aren't "does it have backup?" but "which circuits stay live, and what will they run at the same time?" Get the answer in writing before you sign. If you're still weighing whether a battery is right at all, our best home battery in Australia for 2026 guide and the side-by-side compare tool frame the options by goal, including backup.
Is there a delay, and can solar
recharge it mid-blackout?
Two practical details that matter in a real outage: some systems take a brief moment to pick up the load, and solar can only top the battery up in daylight if the system was set up for it.
The switchover. When the grid drops, a backup-capable system has to detect the loss, island your home and pick up your essential circuits. Some systems do this seamlessly; others have a brief switchover — a few seconds where the power blinks before backup takes over. It's usually harmless, but it's worth knowing if you have equipment that dislikes a momentary interruption. Ask your installer whether your setup is effectively instant or has a short changeover.
Solar recharge. A common hope is that solar will refill the battery during a daytime blackout so your essentials last for days. This is possible — but only if the system is specifically configured for it. It depends on the inverter and gateway supporting solar backup and being set up that way at installation. Many simpler backup setups just run the battery down without any solar top-up, and of course no system can recharge from solar overnight. If riding through a long or multi-day outage matters to you, make solar backup an explicit requirement from the start.
Staying safe when the
power's out.
A blackout is exactly the wrong moment to start poking at electrical equipment. Here's the safe, honest line on what you can and can't do yourself.
All electrical work must be done by a licensed electrician. If your system simply needs a basic reset — for example restarting your inverter via its isolator switch as described in the manufacturer's manual — that's fine to do yourself, but only if it is safe and simple and the steps are clearly documented for your unit. If you're unsure, or anything looks or smells wrong, leave it alone.
For anything beyond a basic reset, call a licensed electrician, your installer, or a CEC-accredited service. Never open the battery or inverter enclosure, never touch DC wiring, never pull apart the switchboard, and never work at height or on a roof to reach equipment. Batteries store real energy even when the grid is down, and DC circuits can remain live — this is not DIY territory. When in doubt, isolate at the main switch only if it's safe and simple to reach, then get a professional out.
If you want to know whether your existing system even has backup, don't test it by pulling the main switch or opening anything — book a licensed electrician or CEC-accredited installer to inspect it properly. It's part of how Jouli, our honest energy advisor, works: safe, real advice, including "don't touch that yourself".
What to ask your installer
about backup.
If keeping the lights on matters to you, these are the questions that separate a real backup system from a savings battery that goes dark in an outage. Ask them up front and get the answers in writing.
Is backup actually included?
Confirm the quote includes a backup gateway and an essential-circuits subboard — not just the battery. If those two aren't itemised, you're likely buying a savings battery with no blackout protection.
Which circuits stay live?
Get the exact list of nominated circuits and, crucially, what they'll run at the same time. Lights, fridge and wi-fi is realistic; the aircon, oven and EV charger together usually isn't.
Is there a switchover delay?
Ask whether backup is effectively instant or has a brief changeover moment, so you know what to expect for any sensitive equipment.
Will solar recharge it?
If you want to ride through a long or daytime outage, confirm the system is configured so your solar keeps charging the battery during a blackout — it isn't automatic.
What's the continuous power?
Get the backup power rating in kW so you can sanity-check it against the loads you care about. Around 3 to 5 kW is common for a single unit.
Do I need more than one?
If you genuinely want whole-home or big-load backup, ask honestly whether that needs a second battery — and what it adds to the price — rather than discovering the limit later.
So — will yours work in a blackout?
Only if it was built to. Decide whether backup matters to you before you buy, and make it an explicit part of the brief — don't assume it comes as standard.
If blackout protection is a priority — you're in an outage-prone area, you work from home, or you rely on medical or refrigeration equipment — then a backup gateway, a well-chosen essential-circuits subboard and (if you want it) solar recharge should be specced in from day one, and you should be clear-eyed that a single battery runs your essentials, not your whole home at once. If outages are rare where you live and your real goal is cutting your bill, a standard install without backup is cheaper and still does the important work. There's no single right answer — just the one that fits your home, honestly costed and clearly explained before you spend a cent.
Battery backup in a blackout
— your questions, answered.
No — not by default. Most home batteries do NOT provide backup power in a grid outage unless backup is specifically designed and installed. A standard grid-connected battery is required to shut down when the grid goes down (an anti-islanding safety rule that protects line workers), so without extra hardware it stops supplying your home in a blackout, just like a grid-tied solar system without a battery. To get backup you need a backup gateway or changeover device plus a nominated essential-circuits subboard wired in at installation. If keeping the lights on matters to you, ask your installer explicitly whether backup is included and exactly what it will run before you buy — do not assume it comes as standard.
Almost always because backup was never fitted. If your system was installed as a standard grid-connected battery without a backup gateway and an essential-circuits subboard, it is designed to shut down the moment the grid fails, so it cannot power your home during an outage even though it is full of stored energy. This is normal and it is a safety feature, not a fault. A few systems that do have backup also need a brief switchover moment and may take a few seconds to pick the load back up. If you expected backup and got none, check your original quote and paperwork for a backup gateway or changeover, and ask your installer to confirm whether your system was ever configured for backup — never open the equipment yourself to investigate.
Usually the essentials, not the whole home at once. Even when backup is fitted, the continuous backup power from a single battery is limited — commonly around 3 to 5 kW — so it is designed to run nominated essential circuits such as lights, the fridge, wi-fi and some power points. That is generally not enough to run large loads like ducted air conditioning, an electric oven, an instantaneous electric hot-water unit, a pool pump or an EV charger at the same time. Whole-home backup is possible but needs deliberate design and often more than one battery, which costs more. The honest questions to ask your installer are which circuits stay live and what they will and will not run together — get that in writing before you buy.
A backup gateway (also called a changeover or automatic transfer device) is the piece of hardware that lets your battery safely disconnect from the grid and keep powering part of your home during an outage. It sits between the grid and your nominated essential circuits, and it is what makes blackout backup possible while still meeting the safety rule that stops power flowing back into the grid. You only need one if backup matters to you — if your main goal is bill savings and you are relaxed about blackouts, a standard install without a gateway is cheaper and still stores and uses your solar normally. If backup is a priority, the gateway plus an essential-circuits subboard needs to be part of the brief from the start, because retrofitting it later usually costs more than including it up front.
Only if the system is specifically configured for it, and only in daylight. Some backup-capable systems can keep your solar running in an outage and use it to recharge the battery during the day, which can extend how long your essentials stay powered through a longer blackout. But this is not automatic — it depends on the inverter and gateway supporting solar backup and being set up that way at installation. Many simpler backup setups run the battery down without solar top-up, and no system can recharge from solar overnight. If riding through a long or multi-day outage matters to you, tell your installer up front and ask specifically whether your solar will keep charging the battery during a daytime blackout.
Check your paperwork and ask your installer directly — do not assume. Look on your original quote, system design and commissioning documents for a backup gateway, changeover, automatic transfer switch or a nominated backup or essential-circuits subboard; if none of those appear, your system very likely has no blackout backup. The most reliable step is to ask your installer to confirm in writing whether backup is fitted, exactly which circuits it powers, and what those circuits will run at the same time. Do not test it by opening the equipment, touching any wiring or pulling the main switch yourself — if you want it verified or added, book a licensed electrician or a CEC-accredited installer to inspect the system safely.