Solar and battery backup for Perth blackouts: what's real and what's not

Solar panels alone do nothing during a blackout. A battery only keeps your home running if it has backup-capable hardware, plus a backup circuit wired in at install: skip either one and the power stays off no matter what's on your roof or in your garage. Get both right, and a well-sized Perth battery typically covers 12 to 24 hours of essential loads with no sun at all.

Perth and regional WA get real outages worth planning around. The 2021 Kalbarri cyclone cut power to roughly 31,500 Western Power customers, and summer thunderstorms bring shorter, more frequent outages across the metro every year. Here's what solar and battery systems actually do when the grid goes down, including the limits that sales conversations tend to skip.

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Why doesn't my solar work during a blackout?

Most Perth homes run a grid-tied solar inverter with no battery. When the grid goes down, the inverter shuts off automatically, even in full sun. That's not a fault: it's a mandatory safety requirement under AS/NZS 4777.2. "Anti-islanding protection" stops the inverter feeding power back into a line that a Western Power crew might be working on.

A home with panels and a standard string inverter (Fronius Symo, Sungrow SG, GoodWe, SMA Sunny Boy) produces zero usable power during an outage, no matter how strong the sun is. It catches out plenty of Perth homeowners who assumed solar alone would keep the lights on.

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What do I need for battery backup during a blackout?

Two things both have to be true. Neither one alone is enough.

1. Backup-capable hardware. A hybrid inverter, or an all-in-one battery with its own backup gateway, that can "island": disconnect from the grid and keep running independently.
2. A backup circuit wired in at install. Either a dedicated essential-loads panel or a whole-home transfer switch, set up during your original installation or a retrofit.

Skip either one and a battery sitting on a standard grid-tied system does nothing when the power goes out. A battery on its own is not blackout protection: the hardware and the wiring both have to be right, and both get decided at install, not afterward.

Backup-capable batteries

Not every battery on the market can do this. Some entry-level batteries are built purely for arbitrage (charge from solar, use at night) and can't operate independently of the grid at all. Confirm backup capability explicitly, brand by brand:

• Tesla Powerwall 3: 13.5kWh usable storage, backing up selected circuits or the whole home on a single-phase supply. On a three-phase Perth home, one Powerwall covers one phase only: whole-home backup across all three phases needs one Powerwall per phase. The earlier Powerwall 2 has a lower continuous output, so treat it as essential-circuits backup unless your installer confirms otherwise for your specific install.
• Sungrow SBR with a compatible hybrid inverter: home backup, with circuit coverage that depends on the inverter and battery pairing.
• Alpha-ESS SMILE systems: back up selected circuits on one phase. The residential range sold in WA isn't built for whole-home backup on a three-phase supply.
• Enphase IQ Battery: uses its own backup controller rather than a hybrid inverter, so the backup hardware is a separate item on the quote. Ask your installer which controller your system needs and exactly which circuits it will cover.

Most backup-capable systems switch over automatically, without you touching anything, though exactly how fast and how smoothly that happens varies by brand and by inverter.

Hybrid inverter plus battery

A hybrid inverter (Fronius Gen24, Sungrow SH, GoodWe EH) keeps operating during an outage by islanding with the battery. During daylight hours it can also charge the battery from the panels while powering loads at the same time, which stretches the effective backup duration.

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How long will my battery last during a Perth blackout?

Consider a typical summer scenario: a 40°C day, a thunderstorm at 5pm, and a blackout running from 5pm to 10am the next day (17 hours). What can a 10kWh battery cover?

Every figure below uses 8.6kWh of usable capacity rather than the 10kWh nameplate, because depth-of-discharge limits and inverter losses take a cut before the power reaches your circuits.

High-demand scenario: running a single split-system AC (1.2kW), a fridge (0.15kW), lighting and phone charging (~0.5kW):

• Combined draw: ~1.85kW
• Battery duration: 8.6kWh ÷ 1.85kW ≈ 4.6 hours
• Battery depleted around 9:30pm: about 12 hours remaining without power

Moderate scenario: fridge, fans, lighting and device charging, no AC:

• Combined draw: ~0.8kW
• Battery duration: 8.6kWh ÷ 0.8kW ≈ 10.5 hours
• Covers most of the 17-hour outage

With solar recharge during the outage: if the outage runs into the next morning and the hybrid inverter is still operating, solar generation from around 8am can recharge the battery while it powers loads. A 10kW system on a clear Perth day typically generates 2–4kW in the 8–10am window, which extends the effective backup duration significantly.

For the full duration formula and an appliance-by-appliance breakdown, see how long your battery actually lasts in a Perth blackout.

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Will my battery back up my whole house or just some circuits?

Perth battery installs typically back up one of two ways:

• Whole home. Every circuit on the switchboard, which needs a transfer switch or a specific switchboard configuration.
• Selected critical circuits. A dedicated backup panel covering a handful of circuits: fridge, lighting, one or two power points.

Which one you get is decided at installation. Whole-home backup costs more (it needs extra switchboard work) and draws harder on the battery during an outage. Most Perth installs use selected critical circuits, or whole-home with the expectation that you'll manage load during an outage.

What this means in practice: if your dishwasher, washing machine and oven sit on non-backup circuits, they won't run during a blackout even with a battery installed. If you're specifically worried about staying connected, solar battery backup for your NBN and internet covers what actually keeps a router and modem alive.

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Can I charge my EV during a blackout?

Almost certainly not. Your EV charger will almost always sit on a non-backup circuit, and EV chargers draw 7–22kW: far more than a single residential battery can sustain. Using your EV itself as backup power (vehicle-to-home, or V2H) needs specific equipment that isn't widely available in Perth residential installs in 2026.

If you need more runway than a battery alone gives you, battery versus generator backup for Perth blackouts is worth reading before you decide.

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How much battery capacity do I need for backup?

For genuine multi-day backup (bushfire evacuation, an extended storm outage), a 10kWh battery with solar recharge can sustain essential loads indefinitely during daylight hours, but overnight draw still limits coverage to whatever the battery itself holds.

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What can I realistically expect from battery backup in Perth?

A well-configured Perth system (10kW solar, 10kWh battery, hybrid inverter, backup mode enabled) will:

• Keep your fridge, lights and critical devices running for 14–21 hours with no solar generation at all
• Extend backup indefinitely during daylight hours via solar recharge, assuming moderate load management
• Keep a single split-system AC running for 7–12 hours if it's the only thing on the backup circuit, or around 4–5 hours alongside a fridge, lights and device charging
• Not power your ducted AC, electric oven, dishwasher or EV charger during a blackout

Most Perth outages are short, an hour or two while a crew clears a line fault. That's genuine, useful backup power for the longer storm-damage events that run half a day or more. It isn't a whole-home power replacement.

Outside of a blackout, that same battery can also earn credits by joining a virtual power plant when the grid needs support, instead of the other way around.

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Standard grid-tied solar inverters shut down during blackouts. Sunshine alone doesn't help without a battery. A hybrid inverter paired with a backup-capable battery, wired into a backup circuit, delivers genuine blackout protection, but the duration still depends on load management. For the storm-damage outages that run half a day or more, a 10kWh battery with solar recharge covers essential loads comfortably. Extended multi-day outages need disciplined load management and, ideally, a larger battery or a generator as backup.