Why batteries don’t all work in a blackout
When the grid goes down, every solar system in the street shuts off – by law – so it can’t push power into lines that workers are repairing. A backup-capable battery system gets around this by disconnecting from the grid entirely and forming its own “island”: the battery (and your solar, in daylight) keeps powering the house behind that disconnect. Systems without islanding hardware go dark with the street, no matter how charged the battery is.
Essentials backup vs whole-home backup
| Essentials circuit | Whole-home backup | |
|---|---|---|
| What stays on | Fridge, lights, wifi, a few outlets | Everything, within the battery’s power limit |
| Extra cost | Modest – some switchboard rewiring | $1,500 – $3,000+ for gateway hardware and wiring |
| How long it lasts | A 10kWh battery can run essentials for 24h+ | Hours under heavy load – or indefinitely with solar recharging by day |
| Best for | Most homes – covers what actually matters | Medical needs, work-from-home, frequent long outages |
The honest advice: most households only need essentials backup. A fridge draws around 1-2kWh a day – a fraction of a 10kWh battery. What kills backup duration is air-conditioning and ovens; if you must run cooling through an outage, you need both capacity (13.5kWh+) and a high-output battery (the Powerwall 3’s ~10kW is the benchmark – pricing here).
The SA angle: heatwaves, bushfires and the Hills
South Australia’s outages cluster exactly when power matters most: heatwave demand peaks and bushfire-season events, especially across the Adelaide Hills and regional feeders. A battery that recharges from solar each day can ride out multi-day events that would exhaust any fuel generator’s tank – silently, with no fuel runs through smoke or 45-degree heat.
If backup matters, tell the installer first
- Say it before quoting – backup shapes the battery choice, hardware and switchboard work. Retrofitting it later costs more.
- Check the VPP reserve. If you join a Virtual Power Plant for the REPS incentive, confirm you can hold a backup reserve (most allow ~20%) – compare SA VPPs.
- Ask what happens mid-blackout in daylight. Good systems keep charging from solar while islanded; cheap configurations don’t.
Figures current as of June 2026. The SA Home Battery Scheme has closed. Source.
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Battery backup FAQs
How long will a 10kWh battery run my house in a blackout?
On an essentials circuit (fridge, lights, wifi), comfortably 24 hours or more – and indefinitely if solar recharges it by day. Running air-conditioning shortens that to hours, which is why backup design starts with what you actually need on.
Do all home batteries provide backup power?
No. Islanding capability varies by battery and configuration, and whole-home backup needs extra hardware. Confirm backup is specified in your quote – it’s the most common post-install regret.
Will my solar panels work during a blackout?
Only with a backup-capable battery system. Solar alone must shut down for line-worker safety. With islanding, your panels keep charging the battery during the outage.
Is a battery better than a generator for backup?
For most homes, yes – instant switchover, no fuel, no noise, no servicing, and it earns savings every day between outages. A generator only wins for very long grid-down events with no sun, or loads beyond a battery’s output.
Related: Batteries in the Adelaide Hills · What size do I need? · Powerwall 3 price in SA