Key takeaways
- Grid-tied inverters are designed to switch off in an outage. This is a safety requirement, not a fault.
- Backup needs a battery and the switching gear that isolates your house from the grid.
- Most backup setups power selected circuits only (lights, fridge, internet), not the whole house.
- A battery adds $8,000 to $24,000 and stretches payback to 10 to 14 years (Solar Scout, 2026).
- If outages are rare where you live, a battery bought only for backup is hard to justify on cost.
Why does my solar stop working when the power goes out?
Because the inverter is required to. Inverters connected to the New Zealand grid have to meet AS/NZS 4777.2, which includes anti-islanding protection: when the inverter senses the grid has gone, it stops exporting within moments. Otherwise your panels could energise a line a lineworker believes is dead.
This catches a lot of new solar owners out the first time there's an outage on a sunny day. The panels are still generating, but with nowhere safe to send the power and no battery to put it in, the inverter shuts down until the grid comes back. It restarts automatically afterwards.
How can I keep the power on with solar in an outage?
There are three practical ways. A battery with a backup gateway disconnects the house from the grid and runs it from storage and solar. A hybrid inverter with a backup (EPS) output powers a small dedicated circuit. Or skip solar entirely for backup and use a generator with a proper changeover switch.
| Option | What stays on | What it involves |
|---|---|---|
| Battery with backup gateway | Selected circuits, or the whole house on larger systems | Battery, gateway that isolates the house from the grid, electrician rewiring backed-up circuits |
| Hybrid inverter with backup output | One small circuit or outlet | A hybrid inverter and a battery; output is limited |
| Generator with changeover switch | Whatever the generator can carry | No solar needed; an electrician installs the changeover switch |
| Standard grid-tied solar, no battery | Nothing | Shuts down until the grid returns |
What does a backup battery cost in NZ?
About $1,219 per kWh of storage installed on average in 2026, according to Solar Scout. A single 13.5 kWh Tesla Powerwall 3 is $19,000 to $24,000 installed, and BYD and Sungrow batteries start from around $800 per kWh. Our battery guide has the full table and payback maths.
Which circuits should a backup battery run?
The ones you'd miss in the first few hours: lights, the fridge and freezer, the internet router, phone charging, and any medical equipment. Ovens, hot water cylinders, heat pumps and EV chargers draw far more power and drain a battery quickly, so most backup setups leave them on the grid-only side.
- Lights and power points in the main living area
- Fridge and freezer
- Router and modem, so phones and internet keep working
- A water pump, if you're on tank water
- Medical equipment, if anyone at home relies on it
Is a battery worth it just for power cuts?
Usually not, unless outages are frequent where you live or someone at home relies on powered medical equipment. A battery mostly pays its way by storing daytime solar for the evening. If backup is your main reason, compare it with a generator, and ask your installer for a hybrid-ready inverter so a battery can be added later.
Frequently asked questions
Do solar panels work during a power outage in NZ?
Not on a standard grid-tied system. The inverter shuts down when the grid fails, as AS/NZS 4777.2 requires. You need a battery with backup for power during an outage.
Can I use my solar panels without the grid?
Only with a battery and backup switching, or a fully off-grid system. A grid-tied inverter on its own can't run the house without the grid.
Does a Tesla Powerwall work in a power cut?
Yes, when installed with its backup gateway, which isolates the house from the grid. It runs the backed-up circuits from the battery and recharges from solar.
Can I add backup to my existing solar?
Yes, by adding a battery and backup switching, but Solar Scout puts payback on a retrofitted battery at 15 years or more.
Will my solar restart after a power cut?
Yes. A grid-tied inverter reconnects automatically once the grid is stable again. If it doesn't, check the solar isolators and the inverter's display.
Sources
- Standards New Zealand, AS/NZS 4777.2 Grid connection of energy systems via inverters: inverter requirements (checked Oct 2026)
- Solar Scout, Solar battery storage NZ (updated 30 Aug 2026) (checked 30 Aug 2026)
- EECA, Learn about home solar tech (inverters, batteries) (checked Oct 2026)
- EECA, Solar quotes and installation (checked Sept 2026)
General information, not financial advice. Prices and rates change; each figure shows where it came from and when it was checked.