When the power goes out, most Australians assume their solar panels will keep the lights on. Unfortunately, that's not how it works. Standard solar systems shut down during blackouts for safety reasons. If backup power during outages is important to you, a battery is the most practical solution — but it's not as simple as just having one installed. Here's what you need to know.
Why Solar Panels Don't Work During Blackouts
This surprises many solar owners, but there's a critical safety reason behind it. When the grid goes down, electricity workers need to repair power lines. If your solar system continued feeding power into the grid, it would create a dangerous situation called "islanding" — energising lines that workers believe are dead.
To prevent this, all grid-connected solar inverters are required by Australian Standards to automatically shut down when they detect a grid outage. This happens within milliseconds. No grid signal = no solar generation. Your panels sit idle on your roof during the very time you might need them most.
How Battery Backup Works
A battery with backup capability uses a device called a backup gateway (or transfer switch) to safely disconnect your home from the grid during an outage. Once isolated from the grid, the battery can power your home without any risk to line workers.
Even better, with the grid disconnected, your solar panels can resume generating — charging the battery and powering your home simultaneously. This means that during a daytime blackout, you can potentially run indefinitely on solar and battery. The topology matters here: our comparison of AC-coupled vs DC-coupled battery systems explains why some setups keep solar running during outages and others don't.
Partial Backup vs Whole-Home Backup
Not all backup systems are created equal. There are two main approaches:
Partial Backup (Essential Loads)
This is the more common and affordable option. A subset of your home's circuits — typically called "essential" or "backed up" circuits — are connected through the backup gateway. During an outage, only these circuits receive power.
| Typically Backed Up | Typically NOT Backed Up |
|---|---|
| Lights (selected rooms) | Ducted air conditioning |
| Refrigerator/freezer | Electric oven/cooktop |
| Internet router/modem | Electric hot water system |
| Phone chargers | Pool pump |
| Garage door | EV charger |
| Security system | Clothes dryer |
| Medical equipment | High-draw appliances |
With partial backup, a 10kWh battery can typically keep your essential loads running for 12–24 hours, or even longer if solar is charging during the day.
Whole-Home Backup
Whole-home backup powers everything in your house during an outage — including high-draw appliances like air conditioning, ovens, and hot water systems. This requires:
- A higher-capacity battery (or multiple batteries)
- A more powerful inverter (to handle peak loads)
- More complex installation and switchboard work
Whole-home backup is significantly more expensive but provides a seamless experience — you may not even notice the grid has gone down.
Cost Premium for Backup Capability
Adding backup to a battery installation isn't free. Here's what the backup component typically adds:
| Backup Type | Additional Cost | What's Included |
|---|---|---|
| Partial backup (built-in) | $0–$500 | Some batteries include backup (e.g., Tesla Powerwall) |
| Partial backup (add-on) | $1,000–$2,500 | Backup gateway/transfer switch + rewiring |
| Whole-home backup | $2,500–$5,000 | Larger gateway, switchboard modifications, load management |
Do You Actually Need Battery Backup?
Before spending extra on backup capability, consider whether you genuinely need it:
You Probably Need Backup If:
- You live in a bushfire-prone area where extended outages are common
- You're in a rural area with unreliable grid supply
- You or a family member relies on medical equipment (CPAP, oxygen concentrator)
- You experience frequent storm-related outages lasting hours or days
- You work from home and can't afford downtime
You Probably Don't Need Backup If:
- You live in a metro area with reliable grid supply
- Your outages are rare and brief (under 2 hours)
- You're primarily getting a battery for financial returns
- You have gas cooking and heating (less dependency on electricity)
Alternative Backup Options
A battery isn't the only way to handle blackouts. Here are alternatives:
Portable Generator ($500–$3,000)
A petrol or diesel generator provides emergency power at a fraction of the cost. Downsides: noisy, requires fuel storage, produces emissions, and needs manual setup. Not suitable for seamless backup but adequate for occasional extended outages.
UPS (Uninterruptible Power Supply) ($200–$1,500)
A UPS provides short-term backup (30 minutes to 2 hours) for specific devices like computers, modems, and medical equipment. It won't run your whole home but can keep critical devices operating until either the grid returns or you set up a generator.
Portable Power Station ($500–$3,000)
Portable lithium battery units (like EcoFlow or Bluetti) can be charged from a wall outlet or solar panel and provide 1–5 kWh of portable power. Useful for camping, events, or as basic emergency backup for lights and devices.
Making the Decision
If you're installing a battery primarily for financial returns, adding backup is a modest extra cost that provides significant peace of mind. If backup power is your primary motivation, compare the total cost of a battery system with backup against alternatives like a generator.
Use our Battery Payback Calculator to model the financial return of a battery, then factor in the backup cost premium to decide whether the complete package makes sense for your situation.