The storm rolls through, the lights go out, and you look up at a roof full of solar panels in the afternoon sun and wonder why the house is dark. It's one of the most common surprises for new solar owners on the Sunshine Coast, usually discovered at the worst possible moment.
Short answer: no, a standard grid-connected solar system does not work in a power outage. It shuts down the moment the grid does, by design, so it can't push power into lines that crews may be working on. To keep power on in a blackout you need a battery that's specified and wired for backup. With backup set up, the system disconnects from the grid, forms its own little grid for your home, keeps your nominated circuits running, and lets the solar recharge the battery during the day.
Here's how that works, what a battery can and can't run, and how to get ready before storm season.
Will my solar system work during a power outage?
If you have solar without a battery: no. If you have a battery, only if it was installed with backup.
That second part catches people out. Not every battery installation includes backup. Some batteries are installed purely to shift solar into the evening and save money, with no backup wiring at all. Those batteries go dark in a blackout too, even though they're full.
If you're not sure whether yours has backup, check your installation paperwork, look for a separate backup or essential-loads section in your switchboard, or ask your installer. Better to find out on a calm day than in the middle of a storm.
Why does solar switch off when the grid goes down?
It's called anti-islanding, and it's a safety requirement for every grid-connected inverter.
When the grid goes down, line crews go out to find and fix the fault. If thousands of rooftop systems kept feeding power into those lines, the "dead" lines wouldn't be dead. Anti-islanding protection makes your inverter detect the outage and stop exporting within moments, so your system can't energise the street.
The inverter also needs a stable reference to work against. A standard solar inverter follows the grid's voltage and frequency. With the grid gone, there's nothing to follow, so it stops.
When the power comes back, the inverter checks the grid is stable for a short period and then reconnects on its own. You don't need to do anything.
What is solar battery backup?
A battery with backup capability does two jobs a normal solar inverter can't:
- It disconnects your home from the grid when an outage happens, so nothing from your house can reach the street.
- It creates its own micro-grid for the circuits connected to it, acting as the reference that your solar and appliances need.
Once your home is "islanded" like this, the battery powers your backed-up circuits, and your solar can keep running to supply them and recharge the battery through the day. That's what turns a few hours of backup into multi-day resilience when storms knock out power for longer.
You'll see backup described in a few ways depending on the brand: a backup port, an EPS (emergency power supply) output, or an essential-loads circuit. They all mean roughly the same thing: some or all of your home is wired to stay on when the grid is off.
How fast does battery backup switch over?
On the systems we fit, it's fast enough that computers don't reboot. Our Deye installs switch over in under 20 milliseconds, and Sigenergy describes its SigenStor as having no load-side disruption. You might see the lights flicker. The Wi-Fi stays up and the fridge keeps running.
Essential circuits vs whole-home backup
This is the biggest decision in any backup design, and it drives both the hardware and the cost.
| Essential circuits backup | Whole-home backup | |
|---|---|---|
| What stays on | A nominated set of circuits, usually on a separate sub-board | Everything on the main switchboard |
| Typical loads | Fridge, freezer, lights, selected power points, internet, often the bore pump on rural blocks | All of the above plus air conditioning, pool pump, oven, hot water |
| Inverter size needed | Moderate | Large enough to start big motors and compressors |
| Battery drains | Slowly | Much faster, especially with air conditioning running |
| Cost | Lower | Higher: bigger inverter, more switchboard work |
| Who it suits | Most households | Large homes, home businesses, medical needs, people who can't go without air conditioning |
Most of our customers choose essential-circuits backup and accept that the ducted air stays off until the grid is back. It keeps the house functional, protects food, keeps the internet and phones going, and stretches the battery much further.
Whole-home backup is entirely doable, but it needs enough continuous output to start an air conditioner or pool pump, which means a larger inverter and often more battery.
What can a battery run in a blackout?
Two numbers decide what a battery can run, and people mix them up constantly:
- Kilowatt-hours (kWh) are the size of the tank. They decide how long you can run things.
- Kilowatts (kW) are the size of the fuel line. They decide how much you can run at once.
In a blackout, the limit is often kilowatts, not kilowatt-hours. Motors and compressors, like those in air conditioners, pool pumps, bore pumps and fridges, pull a surge well above their running draw when they start. If the inverter can't supply that surge, the appliance won't start, or the backup will trip. That's an inverter sizing question, not a battery capacity one.
As a rule of thumb, essentials are easy for most backup systems:
- Fridge and freezer
- LED lighting
- Internet modem and router
- Phone and laptop charging
- TV
- Fans
- Medical equipment on a nominated circuit
Harder loads that need planning:
- Ducted or multiple split air conditioners
- Pool pumps
- Electric ovens and cooktops
- Storage hot water heaters
- EV charging
We ask what you actually want running in a blackout before we quote anything, because that answer shapes the whole design.
How long will a battery last in a blackout?
It depends on the battery size, what's backed up, how much power those circuits draw, and whether the sun is out to recharge it.
With essentials only, a battery can run for many hours, and with solar recharging during the day it can carry you through a couple of days or more. With whole-home backup and air conditioning running, it drains far faster.
Night-time outages are the hardest test, because the battery is on its own until sunrise. A storm that knocks out power at 6pm, when the battery is already being drawn down for the evening, is a very different situation from one at 10am on a sunny day.
For the numbers on a typical size, see our guide on how long a 10kWh battery lasts.
Storm season on the Sunshine Coast: getting ready
Summer storm season is when backup matters most here. Storms bring down lines, trees fall across them, and outages on some streets, particularly in the hinterland and on rural blocks at the end of long feeders, can run longer than people expect.
If you have a battery with backup, a few things are worth doing before the storm season starts:
- Know what's backed up. Walk the house and check which lights and power points stay on. Label them if they aren't already.
- Raise the backup reserve before a storm. Most systems let you set a minimum charge level the battery keeps in reserve for outages. Raising it ahead of a forecast storm means the battery is full when the power goes, rather than drained by the previous evening.
- Check your monitoring. Make sure the app is connected and the system is reporting normally. A battery that's been offline or faulted for weeks won't save you.
- Don't switch things off. Leave the system alone during an outage. It's designed to manage the switchover and the reconnection itself.
- Go easy on big loads. Once you're on battery, hold off on the oven, dryer and air conditioning if they're on backed-up circuits, and the battery will last much longer.
If you don't have a battery, the honest advice for storm season is simpler: assume the solar will be off in a blackout, and plan as you would without it.
What about a generator?
A generator can be a good companion to a battery on rural properties, and off-grid systems commonly include one. But a generator must be connected through a properly installed inlet and changeover arrangement by a licensed electrician. Never plug a generator into a power point to feed the house. It can backfeed into the grid and put line workers at serious risk, and it can damage your solar and battery equipment.
Can I have a home battery without solar panels?
Technically, yes. A battery can charge from the grid, for example on a cheaper overnight or off-peak rate, and provide backup in an outage. But without solar, there's no free daytime energy to store, so the savings case is much weaker.
There's also a rebate catch. The federal Cheaper Home Batteries Program is for batteries connected to new or existing solar. According to the federal energy department, battery systems installed without solar that only store energy from the grid are not eligible.
We go through the pros and cons in detail in our guide to a home battery without solar panels.
Adding backup to a system you already have
If you already have solar and want blackout protection, you usually don't need to replace your panels.
- Healthy inverter under about 8 years old: an AC-coupled battery with backup can go in alongside it.
- Failing or out-of-warranty inverter, or you're expanding the array: replace it with a hybrid inverter and go DC-coupled, with backup built in.
- New solar and battery together: a DC-coupled hybrid is the most efficient option and gives you one point of contact for warranty.
Either way, the backup circuits need to be planned at the design stage, because they involve switchboard work. Our guide to adding a battery to existing solar covers the retrofit options, and our solar battery installation on the Sunshine Coast page explains how we size batteries and which brands we fit.
Frequently asked questions
Will my solar system work during a power outage?
Not on its own. Grid-connected solar inverters must shut down when the grid fails, so they can't send power into lines that crews may be repairing. To keep power during an outage you need a battery installed with backup, which disconnects your home from the grid and runs your nominated circuits from the battery and solar.
Can I have a home battery without solar panels?
Yes, a battery can charge from the grid and provide backup in an outage, but without solar the savings are much smaller. The federal Cheaper Home Batteries rebate also doesn't apply to battery systems installed without solar that only store grid energy. See our guide to a home battery without solar panels for the full picture.
Does every solar battery provide backup power?
No. Backup has to be specified and wired at installation. Some batteries are installed only to shift solar into the evening and will switch off in a blackout like the rest of the system. Check your paperwork or switchboard, or ask your installer.
Can a battery power my whole house during a blackout?
It can, if the system is designed for whole-home backup with an inverter large enough to start air conditioners, pool pumps and other big loads. Most households choose essential-circuits backup instead, which keeps the fridge, lights, power points and internet running for much longer on the same battery.
Does solar keep charging the battery during a blackout?
Yes, if your system has backup. Once the home is islanded from the grid, the solar keeps running to supply your backed-up circuits and recharge the battery during daylight, which is what lets a battery carry you through multi-day outages.
