Can solar and battery power your Perth home during a blackout?

Yes, but only if your system has the right hardware and the right wiring, not just because you own solar panels or a battery. A standard grid-tied inverter shuts itself off the moment the grid goes down. That's a safety rule, not a fault, so rooftop panels alone produce nothing you can use in a blackout. A battery wired in the ordinary way does nothing either.

To actually keep the lights on when the grid drops, you need two things installed together: a backup-capable inverter (or an all-in-one battery with a backup port) and a backup circuit, either a small essential-loads board or a whole-home transfer switch, wired in by an electrician at install. Skip either half of that pair and a blackout still means no power, battery or no battery.

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Why does my solar system shut off during a blackout?

Standard grid-tied inverters continuously monitor the grid's voltage and frequency. The moment grid power goes off, the inverter detects the loss and shuts down within milliseconds. This is deliberate: it's called anti-islanding protection, and it stops your solar system from energising a line that lineworkers assume is dead. Without it, someone repairing a "dead" grid could be seriously hurt.

Result: a standard solar system without battery backup generates zero electricity during a blackout, even on the sunniest day.

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What do you need for battery backup during an outage?

Minimum required:

1. A battery system
2. An inverter with backup or island-mode functionality
3. A transfer switch or backup switchboard that isolates your home from the grid when backup activates

Not every battery ticks these boxes. Some are "grid-dependent": they store and discharge electricity just fine, but they need the grid present to operate. Those shut down along with the solar when the grid fails.

Battery systems with backup capability commonly quoted in WA:

• Tesla Powerwall 3, an all-in-one unit that backs up one phase per unit. A single-phase home needs one Powerwall; a three-phase home needs one per phase for full whole-home coverage. (Tesla's earlier Powerwall 2 is the superseded model, and it has a lower continuous output. If you're comparing the two, our Powerwall 2 vs Powerwall 3 guide covers the practical differences, including the WA rebate gap.)
• Sungrow SBH series with backup output
• Sigenergy systems with backup functionality
• Alpha ESS systems with backup output
• Fronius Gen24 hybrid inverter paired with a battery, though this pairing needs extra switchover hardware fitted at install

When you're getting a battery quote, ask directly: "Does this system provide backup power during a grid outage?" and "Does it work in island mode with solar generation during the day?"

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Whole-home backup or partial backup: what's the difference?

Whole-home backup: The entire home's circuits connect to the backup output, so during an outage the battery runs everything the house normally uses. Genuine whole-home coverage often takes more battery capacity than a single entry-level 10kWh unit, and how much more depends on both the brand and whether your home is single-phase or three-phase. Some inverters only offer whole-home backup on a three-phase supply at all, regardless of how big a battery you pair with them. Ask your installer for the specific minimum capacity your chosen system needs before you assume whole-home coverage is included.

Partial or essential backup: Only designated circuits (lights, fridge, phone charging, internet) connect to the backup panel. The rest of the home has no power. This is the more common setup for cost reasons: you're not trying to power an entire house from one battery.

Common essential backup circuits:

• Refrigerator: 2 to 4kWh/day
• Lighting (LED): 0.3 to 0.8kWh/day
• Phone and device charging: 0.2 to 0.5kWh/day
• Internet router: 0.2 to 0.3kWh/day
• Total essential load: approximately 3 to 5kWh/day

At that average, a 10kWh battery covering essential loads runs for roughly 2 to 3 days without recharging. Note that a 10kWh battery gives you about 8.6kWh of genuinely usable capacity once depth-of-discharge limits and inverter losses are taken out, and every figure here is based on that. For the full arithmetic on your own appliances, see how long your battery lasts in a Perth blackout.

Your NBN router is one of the easiest circuits to keep alive on backup, but whether your internet actually keeps working depends on your connection type too. Solar battery and NBN backup in Perth covers what works and what doesn't.

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Does solar keep charging the battery during a daytime blackout?

If the outage happens during daylight and your system supports solar charging in island mode, yes: the panels can charge the battery while it powers your home. That extends backup duration significantly.

Example (daytime blackout, summer):

• 6.6kW solar generating 5kW
• Backup load: 2kW (fridge, lights, fans)
• Net battery charge rate: 3kW surplus flowing into the battery
• Effective backup duration: unlimited while the sun is up, and the battery tops up for the night ahead

Night-time blackout: No solar generation here: the battery runs on stored charge alone. At the light 3 to 5kWh/day essential-only average from the table above, a 10kWh battery stretches to roughly 2 to 3 days. Run more than bare essentials at once, say the fridge cycling alongside several lights, a TV and some fans at a steady 2kW, and the same 10kWh battery lasts about 4 hours instead. The gap isn't a different battery: it's how much you draw at once. More load running together always means a shorter runtime.

Extended multi-day outage: The critical factor is whether solar can recharge the battery each day. On an average Perth day (5 peak sun hours, after roughly 15% of system losses), 6.6kW of solar generates around 28kWh, comfortably clearing a 5kWh/day essential load with plenty to spare. In summer you get more again, because Perth's peak sun hours run well above the annual average. Multi-day backup is viable as long as the inverter supports island mode with solar charging.

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How often does Perth actually lose power?

Perth's grid is generally reliable. Major outages are typically caused by:

• Summer storm damage to distribution lines
• Planned network maintenance, notified by Western Power in advance
• Equipment failure, which is rare

Most Perth households see the odd short outage rather than a run of long ones: a storm knocks out a line for an hour or two, the network crew fixes it, life goes on. Extended multi-day outages are rare outside major cyclone events in WA's north, well away from the Perth metro grid.

Is battery backup worth paying for?

For the typical short, infrequent Perth outage, a battery with genuine backup capability earns its keep on convenience alone. For a multi-day event, the same battery still holds up through summer provided solar keeps recharging it each day, as above. Realistically, backup is a secondary benefit riding along on a battery bought primarily for bill savings: the payback case rests on daily self-consumption and Midday Saver-style tariff shifting, with backup as a bonus rather than the reason to buy. If you're weighing that payback case, virtual power plants in Perth walks through how a backup-capable battery can also earn credits during grid events, on top of the everyday savings.

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What won't a backup battery run during an outage?

Air conditioning during blackout: Ducted air conditioning systems (4 to 6kW) draw too much for standard 10kWh batteries. Essential backup setups typically exclude air conditioning. On a hot Perth day without power, fans (20 to 100W) are the realistic backup cooling option.

Electric cooking: An electric oven (2 to 3kW) running for 45 minutes uses 1.5 to 2.25kWh from the battery. Technically doable from backup, but not recommended for extended outages where you want to protect battery reserve. Gas cooking keeps a practical edge during blackouts for exactly this reason.

Hot water: Heat pump hot water draws 1 to 3kW for one to two hours: in backup mode, that can be more than you want running continuously. Electric resistive hot water (3.6 to 4.8kW) draws even more. Best avoided during backup.

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What should you ask before buying a battery for backup?

1. Does this specific product support backup or island mode?
2. Is it configured for whole-home backup or partial backup?
3. Does the solar keep generating during an island-mode blackout?
4. What's the backup switchover time? (Milliseconds is ideal. Some systems take several seconds, which resets digital clocks and can trip up sensitive devices.)
5. Is the backup output the same as the main output, full rated power, or is it limited?
6. Does backup require a separate electrician install of an isolating transfer switch?

If you're weighing a battery against a simpler backstop, our battery vs generator comparison lines up cost, noise, run time and what each option actually protects. And for the wider picture of what solar and battery systems really do and don't do in a Perth blackout, see our companion guide, solar and battery backup for Perth blackouts: what's real and what's not.

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Backup capability has to be specified and configured during installation. Confirm the details with your installer and the specific product documentation before buying for backup purposes.