Home batteries and solar in New Zealand

A home battery does two quite different things, and the case for buying one usually rests on one of them rather than both. Separating them makes the decision much easier.

The economic job

Without a battery, midday surplus is exported at your retailer's buy-back rate, and the evening peak is imported at your retail rate. Those two prices are a long way apart, and that gap is the subject of the buy-back page.

A battery closes it. Surplus goes into storage instead of out to the grid, and comes back out at six o'clock instead of being bought. The value of each stored kilowatt hour is the difference between what you would have been paid and what you would have paid, not the retail rate itself, which is the error that makes battery payback calculations look better than they are.

Nationally, importing cost 42.04c per kWh including GST as at May 2026, and more in expensive network areas. The buy-back rate is your retailer's, and you have to ask them for it. The gap between those two, multiplied by the surplus you actually have to store, is the annual return.

Two things limit it:

• You can only store the surplus you have. A house that self-consumes most of its production already has little for a battery to do.
• You can only use what you can shift to. Storage beyond your evening consumption sits idle.

The practical job

Backup during a power cut. This is a genuine, non-financial reason to buy one, and in some parts of New Zealand it is the main reason.

But it does not come automatically. A standard grid-connected system shuts down during an outage for line-worker safety, battery or not. Keeping power requires an inverter configured for backup and usually a dedicated essential-loads circuit: lights, fridge, internet, maybe one heat source rather than the whole house.

If backup is why you are buying, say so early and get it specified in writing, including which circuits stay live and for roughly how long.

The two questions to settle before quotes

1. Which job am I buying? Economics, backup, or both. It changes the specification, and a battery bought for savings and quietly not configured for backup is a disappointment that surfaces during the first storm.

2. Now or later? A hybrid inverter can take a battery later; a plain string inverter generally cannot without being replaced. The hybrid costs more up front. If a battery is likely within a few years, that premium is usually cheaper than replacing the inverter, and if it is not likely, it is money spent on optionality you will not use.

What we do not publish

Battery pricing, brands, or comparisons between them. We hold no verified data on any of it, and this site does not assert things it has not checked. Cost comes from quotes; the value side of the calculation you can do yourself from your own bill and your retailer's export rate, before anyone comes to look at the roof.

What to ask

• Is backup included, which circuits, and for how long?
• What is the warranty, in years and in throughput, and what capacity does it guarantee at the end?
• What is the usable capacity, as distinct from the nameplate figure?
• Does the battery need its own network approval, and is that in the price?
• What happens to the system if the battery fails out of warranty: does solar keep working?