Does solar keep working during a power outage in Perth?

It's a bright, sunny Perth afternoon. The power goes out. Surely your solar panels are still generating — so why did everything in the house just turn off?

This surprises many new solar owners, and the explanation matters if you're deciding whether to add a battery.

Grid-tied solar shuts off during outages — by design

Standard grid-tied solar systems — the vast majority of Perth installations — automatically shut down when the grid goes down. Your solar panels may be generating at full capacity, but your inverter disconnects from the loads in your home.

This isn't a fault. It's a safety requirement under Australian Standard AS4777.2, which governs grid-connected inverter energy systems.

Why? When Synergy or Western Power's lines are down for fault repairs, there are technicians physically working on those lines. If solar systems continued feeding power into the grid during an outage, they could re-energise the lines and create an electrocution risk for the crews doing the repair work. This is called "islanding" — the solar system creating its own little power island while connected to the supposedly-dead grid.

All grid-tied inverters sold in Australia must have anti-islanding protection that detects when the grid is absent and shuts down within milliseconds. This is automatic and cannot be overridden in a standard grid-tied system.

Practically: A grid-tied solar system with no battery provides zero backup power during a blackout. The sun could be shining perfectly and your inverter will not supply your house.

What makes a system provide backup power?

Backup power during a blackout requires two things:

1. A battery with backup (islanding) capability — The battery must be able to operate in "island mode," disconnected from the grid, while continuing to supply your home. Not all batteries include this — check the specification sheet and ask your installer explicitly.

2. A grid disconnect mechanism — Either a dedicated automatic transfer switch (ATS) or the inverter's built-in isolation relay that separates your home from the grid the moment the outage is detected. This allows your battery-inverter to create the "island" safely without risk to lineworkers.

When both are in place, the sequence during an outage is:

1. Grid voltage drops (outage begins)
2. Inverter detects the outage within milliseconds
3. Isolation relay disconnects your home from the grid
4. Battery-inverter switches to island mode
5. Your home (or the backed-up circuits) continues running from the battery

This happens automatically in a well-configured backup system — the transition is fast enough that most devices (phones, fridges, lights) don't notice.

Which Perth battery systems support backup?

Battery capability varies by product and configuration:

Tesla Powerwall 2: Includes backup capability as standard. When the Powerwall is installed with the whole-home backup gateway, the entire home is backed up. This is one reason the Powerwall has strong brand recognition for backup use cases.

Sungrow hybrid systems (SH series): Support backup, but the backup wiring scope (whole-home or selected circuits) depends on the installation configuration. Confirm with your installer what's backed up.

Growatt hybrid systems: Support backup, typically configured as selected backup circuits (not necessarily whole-home).

Enphase IQ Battery + IQ System Controller: Provides backup capability, with the system controller managing the transition.

Alpha-ESS systems with backup configuration: Backup available with the right inverter and wiring.

AC-coupled batteries (battery added to an existing solar system): Performance during backup depends on the specific battery and whether the existing solar inverter can run in island mode. This is a common complication when adding a battery to an existing solar system — the original grid-tied solar inverter may not be compatible with the new battery's backup mode. Ask your installer to confirm.

Note on Tesla Powerwall 3: The Powerwall 3 integrates the solar inverter into the unit. Its backup capability should be confirmed with your installer and current Tesla documentation, as specifications for newer products evolve.

What can you run on a 10kWh battery during a blackout?

A 10kWh battery with backup doesn't mean unlimited power — it depends on what's drawing from it and for how long.

| Appliance | Typical draw | Hours from 10kWh (alone) | |---|---|---| | Fridge (modern) | 150W | 60+ hours | | LED lighting (5 lights) | 50W | 100+ hours | | Phone/laptop charging | 50–100W | 50–100 hours | | CPAP machine | 30–50W | 100–200 hours | | Ceiling fan | 50W | 100 hours | | Small television | 100W | 50 hours | | Reverse-cycle AC (3.5kW unit) | 1,000–2,500W | 4–10 hours |

Key insight: Essential loads (fridge, lights, phone, CPAP) can be sustained for days from a 10kWh battery. Air conditioning is the single biggest draw and dramatically reduces backup duration.

If you have solar during daylight hours and your battery has backup mode, the solar can recharge the battery during the day — giving you essentially indefinite backup for low loads on a sunny day.

Perth's blackout context

Perth experiences more extended outages than most Australian capitals due to:

• Bushfire season (December–March): fire events can take down transmission lines for days in affected areas
• Storm damage: strong autumn/winter storms (April–June) bring fallen trees on lines
• Network maintenance: Western Power manages an ageing distribution network in parts of outer metro Perth

For households in bushfire-risk areas (Hills, Dunsborough, Margaret River, outer southern suburbs), battery backup capability has real practical value. It covers both short local outages and multi-day evacuation scenarios where the grid may be down.

Does backup capability affect the WA Battery Scheme rebate?

No. The WA Battery Scheme rebate ($130/kWh, up to $1,300) applies to eligible batteries regardless of whether they're configured for backup. Backup capability doesn't disqualify a battery from the scheme.

The battery must still be on the WA SSL approved product list and installed by a CEC-accredited installer. See our WA Battery Scheme guide for full eligibility details.

Should backup capability affect your battery choice?

If backup power is a priority, make backup capability a requirement — not an afterthought — when getting quotes. Ask each installer:

1. "Does this battery support backup mode?"
2. "What circuits are backed up — whole home or selected circuits?"
3. "How does the backup mode interact with the solar system during a blackout?"
4. "What happens to backup if the battery is depleted — does solar recharge it automatically?"

A battery without backup capability may cost less, but it provides no blackout protection — you'd have a battery that optimises self-consumption and runs into the grid, nothing more.

The price difference between a basic battery and a backup-capable equivalent is typically $500–1,500 depending on brand and installation complexity. For households in high-outage-risk areas or with medical equipment that requires uninterrupted power, this premium pays for itself quickly in avoided costs and inconvenience.

Backup capability and configuration varies by product version, firmware, and installation. Always confirm backup specifications with your installer before signing a contract. AS4777.2 anti-islanding requirements are mandatory for all grid-connected systems in Australia.