A 5 kW solar PV system in NZ costs around $11,000–$14,000 installed in 2026. Add a 10 kWh battery and you're looking at $24,000–$30,000. That's roughly 3× the upfront for 1.5–1.7× the savings — because you're now storing power that you would otherwise have exported for $0.08–$0.17/kWh.
Batteries are worth it if:
- Your retailer's buy-back rate is below $0.10/kWh
- You're in a part of NZ with frequent power cuts and want backup
- You have a variable-rate plan (Octopus Spot, etc.) and can charge from cheap overnight rates
- You can pair it with an EV that exports back to the home (V2H — coming, not standard yet)
Batteries are not worth it if:
- You're on a high buy-back rate already
- You're using solar mostly for daytime export (no battery cycles)
- You can't stretch the budget — a bigger PV array is almost always a better $/kWh saved
If a salesperson tells you "you save the same money with a battery as without", ask them to email you the model. They won't.