One of the biggest reasons Australian homeowners install a battery is blackout protection. It sounds simple. The grid goes down, the battery takes over, life continues. Right?
In practice, it’s one of the least understood parts of buying a battery, and it catches a lot of people out. Two homes can install the exact same size battery and have completely different experiences the first time the power actually goes out.
If black out protection is something you want for your home battery, here’s what you need to know.
What is Blackout Protection?
Blackout protection, sometimes called backup power, is the ability of your solar and battery system to keep your home running when the grid goes down, instead of losing power along with everyone else on the street.
It’s not something every solar system does automatically. A standard grid connected solar system, even a large one, is designed to shut itself off completely during a blackout for safety reasons.
To get backup power for your home, your battery needs to be specifically installed and configured for it, and even then, how much of your home stays powered and for how long depends on a few things most people never think to ask about.
A Battery Doesn’t Automatically Mean You Will Have Backup Power
This is the first thing to check, and don’t assume the answer is yes.
A battery can be installed three different ways:
No backup. The battery still saves you money day to day, but if the grid goes down, your house loses power along with the rest of the street.
Partial home backup. Only selected circuits stay powered, usually things like the fridge, lights, internet and a few power points. Power hungry appliances like air conditioners, ovens and EV chargers are often left off.
Whole home backup. Every circuit in the house stays connected, provided you stay within what the system can actually supply. That last part matters more than people realise, which is what the rest of this comes down to.
So the real first question to ask an installer isn’t whether a battery can provide backup. It’s whether the quote in front of you actually includes it, since it isn’t always in cheaper quotes.
The Inverter is in Control
Before getting into the difference between partial and whole home backup, there’s one thing you need to know first. Your solar inverter is what decides how much power your home can draw during a blackout.
A solar inverter’s job is to convert the electricity your system generates into a form your home can actually use. It comes with a rating of how much power it can push into your home at a time.
For example, a 5kW inverter puts out roughly 21 amps. That sounds like a lot until you start adding things up. A kettle alone can pull 2 to 2.4kW. Add a microwave and you’re already using half that limit before touching anything else in the house.
If you go over the limit of your inverter capacity, the system doesn’t get slower, it trips and shuts down completely.
Partial Home Backup vs Whole Home Backup
The traditional approach: partial home backup
Historically, this has been the default way to backup your home during a power outage. Backup circuits are connected to the inverter and run through that circuit 24/7.
The problem is, even while the grid is working normally, those backup circuits are capped at the inverter’s limit. Put too much of the home behind that limit and you get nuisance tripping every time a few appliances run together, blackout or not. Very frustrating for homeowners.
So installers have traditionally played it safe by nominating only the essentials, things like the fridge, lights and internet, and leaving everything else off the backup circuit.
The result: only some items of your home will receive power during a blackout.
The newer approach: whole home backup with a bypass
More recently, brands including Tesla, Sigenergy, GoodWe ESA and the latest Sungrow models have introduced something called a bypass, and it’s changed what’s realistic to back up.
A bypass doesn’t supply power itself. It’s more like a set of points on a railway track, deciding which line your power travels down. While the grid is connected, the points are set so your backed up circuits draw straight off your normal household supply, running past the inverter’s limit altogether. That’s what removes the nuisance tripping problem, and it’s why installers can now comfortably connect far more of the home, often the whole home, to the backup supply.
In most cases, this makes a bypass system the more convenient option. You’re not stuck worrying about accidentally tripping the system every time you run the kettle and the air conditioner together on a normal day, and because that everyday risk is gone, installers can put more of your home behind the backup supply with confidence.
The catch: whole home backup still has a ceiling
Whole home backup doesn’t mean unlimited power. The moment the grid actually goes down, the bypass disengages and the inverter takes over supplying everything on its own. From that point, your maximum available power is the inverter’s backup rating, which is very often the same as the inverter’s overall size.
This is where people get caught out. You can have every circuit in the house wired into a whole home backup system, but if it’s sitting behind a 5kW inverter, you’ve still only got 5kW to work with the moment the power goes out. Whole home wiring doesn’t change that.
So if whole home backup matters to you, the inverter needs to be sized for it. A larger inverter, alongside having a bypass, is what actually lets you run more of the house at once during a blackout.
Will My Solar Keep Charging the Battery During a Blackout?
This is the one that surprises most people. Having solar panels on the roof doesn’t mean they’ll do anything during a blackout. A standard grid connected solar inverter is designed to shut itself off the moment the grid fails, so it can’t feed power back into a network that’s meant to be dead.
Whether your solar keeps working comes down to how it’s connected.
If your solar and battery share one hybrid inverter (a DC coupled system), the pair can typically create their own mini grid once safely disconnected from the street. Solar can then keep powering the house and topping up the battery through the outage, which can be the difference between a battery lasting one evening and one lasting several days.
If your battery was added later alongside an existing solar inverter (an AC coupled or retrofit system), that original solar inverter often shuts down with the grid, leaving the battery to work alone on whatever charge it already had. Some AC coupled setups are specifically designed to keep solar running too, but it has to be built that way rather than assumed.
Either way, the better question to ask isn’t “does my battery have backup.” It’s “will my solar keep producing and recharging my battery once the grid is down.”
How Long Will My Power Last During a Blackout?
This is really two separate questions.
How much power you can draw at once is the inverter question above. How long that power lasts depends on how much usable energy is in the battery and how hard you’re using it. Running just the fridge, lights and internet can stretch a battery for a very long time. Add air conditioning or an oven into the mix and the same battery might not last the night.
There’s also a simpler factor that’s easy to overlook: how charged the battery already was when the blackout started. A large battery that’s already been drawn down overnight won’t help much the next morning. If backup is a priority for you, ask your installer about setting a reserve, which keeps a portion of the battery held back specifically for outages rather than letting it run flat on everyday use.
The Questions Worth Asking Before You Sign a Quote
Does the quoted price actually include backup, not just a battery that’s technically capable of it?
Is it partial or whole home backup, and if partial, exactly which circuits are covered?
If it’s whole home backup, does the system use a bypass, and is the inverter actually sized to make the most of it?
What is the inverter’s backup rating, not just its overall size?
Will my solar keep working and recharging the battery if the grid goes down?
If I’m on three phase power, which phases and circuits stay live during an outage?
Can I set a reserve to protect some capacity specifically for blackouts?
The Bottom Line
Backup power is one of the best reasons to install a battery, and also one of the easiest things to get wrong when comparing quotes. The battery’s size on paper tells you almost nothing about what will actually happen the next time the power goes out. What matters is whether you’ve got partial or whole home backup, whether the system uses a bypass, whether the inverter is actually sized for what you’re asking it to do, and whether your solar can keep working once the grid disappears.
Get clear answers to those before you sign anything, and you’ll know exactly what your home will do when the lights go out.
This is also exactly the kind of thing that’s hard to get a straight answer on over the phone from a call centre, since it depends entirely on your home, your existing system and how everything is wired together. It’s why Solar Guide Australia only lists a small, hand picked shortlist of local installers in each area rather than putting you in front of everyone who’s willing to pay for the lead. The installers on our directory have the experience to walk you through your own setup properly, not just tell you what you want to hear to get the sale.
