The storm passes, the power’s still out, and it’s a clear sunny morning. Your panels are up there on the roof, generating precisely nothing for you. If that’s happened to you, you already know the uncomfortable truth behind how to choose a solar battery for power outages in New Zealand: the battery is the easy part, and it’s the least likely thing to go wrong with your plan.
How to Choose a Solar Battery for Power Outages in NZ
Most guides start with kilowatt-hours. This one starts with the reason your existing system left you in the dark, because getting that wrong makes every other decision pointless.
The short answer: the battery is only half of it
Choosing a battery for outages means matching usable capacity to the outages you actually get but the system around the battery decides whether you get backup at all. Without a hybrid inverter with islanding capability, a properly configured switchboard and dedicated backup circuits, a battery won’t power your house when the grid drops.
Ask about that first. Capacity second.
Why your solar panels switch off in a power cut
Standard grid-tied solar systems shut down automatically when the grid fails. This is called anti-islanding, and it’s a safety requirement, not a fault: if your inverter kept pushing power into the network, it could energise lines that a line worker believes are dead.
So the panels stop. Not because they can’t generate, but because they’re not allowed to feed a dead grid.
Backup capability is what changes this. A system with it disconnects from the network, forms its own small grid inside your house, and keeps running from the battery and your panels. Same panels, different system design.
What “backup capability” actually requires
Three things, and you should ask an installer about each by name:
- A hybrid inverter with backup capability: a backup gateway or EPS output, depending on the brand. Not every hybrid inverter includes it.
- A switchboard configured for backup: the electrician separates the circuits you want powered during an outage onto their own board.
- Proper isolation and certification: so the changeover is safe and compliant.
A battery bolted onto a system without those is a bill-reduction device, not a backup system. It’s the single most common misunderstanding we see.
Whole-home backup vs essential circuits
Almost nobody backs up an entire house. It’s expensive, and it means a battery draining into your oven and your heat pump during exactly the period you need it to last.
Instead, you pick circuits. The common set:
- Fridge and freezer
- Lighting in main living areas
- Internet router and device charging
- Water pump, if you’re on tank or bore supply
- Any medical equipment
Decide this before you get quotes, because it changes the switchboard work and therefore the price.
Start with the outage, not the battery
Three questions decide your capacity, and none of them are about your solar system.
How often do you lose power? Twice a year or twice a month are different problems. Northland, the Coromandel, Hawke’s Bay, the West Coast and rural Bay of Plenty all see more extended outages than the main urban centres.
How long do outages last? A four-hour cut and a three-day storm event need very different systems.
What genuinely has to keep running? Write the list. Be strict about it.
Work out your essential load
This is simpler than it sounds. A fridge, some lighting, a Wi-Fi router and phone charging typically add up to around 3–4 kWh per day. That’s your baseline.
Then add what’s specific to you:
- Water pump on a rural property: critical, and a surge load (more on that below)
- Medical equipment: changes the whole decision; this is no longer a convenience purchase
- Heat pump: a large continuous load; most households accept going without during an outage
- Electric hot water: heavy. Usually left off backup entirely
How much capacity do you need?
| Your outages | Essential daily load | Usable capacity | Indicative installed cost | Solar recharge needed? | Verdict |
|---|---|---|---|---|---|
| A few hours, occasional | 3–4 kWh | 5 kWh, or a portable unit | Lower end, or a power station | No | Portable may be enough |
| Overnight, a few times a year | 3–4 kWh | 5–10 kWh | Mid | Helpful | Small installed system |
| 1–2 days, storm-prone area | 4–6 kWh | 10–15 kWh | $8,000–$18,000 range | Yes | Installed hybrid system |
| 3+ days, rural | 5–8 kWh with pump | 15 kWh+ | Upper end | Essential | Hybrid system sized for recharge |
Two things the table can’t show.
Usable capacity isn’t nameplate capacity. A battery rated at 10 kWh gives you less than 10 kWh in practice, because manufacturers reserve a portion to protect cell life. Ask for the usable figure, not the headline one.
Beyond about 24 hours, recharging matters more than size. A typical hybrid setup gives roughly 8–12 hours of normal household use, or around two to three days on essentials at 10 kWh which covers the large majority of New Zealand outages. Past that, what keeps you going is your panels recharging the battery each day, not a bigger battery. That’s why battery-only backup without solar has a hard ceiling.
The specs that actually matter
In order of how much they affect you during an actual outage.
Continuous output and surge rating
The most overlooked spec, and the one most likely to leave you disappointed. Capacity decides how long you last; output decides what you can run.
Motors fridge compressors, water pumps, freezers draw several times their running wattage for a moment at start-up. If the surge rating is too low, the pump simply won’t start, no matter how much energy is sitting in the battery.
If you’re on a bore or tank supply, this spec matters more than capacity. Ask for both the continuous output and the surge figure, and give your installer the pump’s details.
Chemistry and cycle life
Most current home batteries use lithium iron phosphate (LiFePO4), which is favoured for its thermal stability and long cycle life. Depth of discharge how much of the capacity you can actually use per cycle varies by product and affects both usable capacity and longevity.
Treat generic cycle-life claims with caution. A “6,000 cycle” number tells you little without knowing the conditions it was measured under. The manufacturer’s warranty terms are more informative: they state what capacity retention is guaranteed, for how long, and under what usage.
Warranty, and who honours it here
A ten-year warranty is only as good as the entity standing behind it in New Zealand. Ask three things: who handles a claim, whether the product has local support or you’re dealing with an overseas manufacturer, and whether the installer’s workmanship warranty is separate from the product warranty.
Batteries are heavy, awkward and expensive to ship. This question is worth more than a small price difference.
Installed battery or portable power station?
Not everyone needs a wired system, and it’s worth being honest about that.
A portable power station is a battery, inverter and charger in one box. No installation, no electrician, no consent. It works the day it arrives, you plug appliances into it directly, and it comes with you if you move. Many accept solar input, so you can recharge from a portable panel during a long outage. It covers a fridge, lights, router and charging comfortably for a night or two.
An installed hybrid system switches over automatically you may not even notice the grid went down powers whole circuits rather than individual appliances, holds far more energy, and recharges from your roof panels every day.
The honest split: if your outages are occasional and short, and you’re willing to plug things in manually, a portable unit does the job for a fraction of the cost. If outages are frequent, long, or you have a water pump or medical equipment, you want the installed system.
What it costs in New Zealand
Adding a battery typically puts $8,000–$18,000 onto a solar installation. Installed pricing in New Zealand has held near $1,220 per kWh since 2024, with brands ranging roughly $800 to $1,780 per kWh depending on size and make.
A question we get constantly: global battery cell prices have dropped sharply, so why haven’t NZ prices? Because the cells are a minority of what you’re buying. The rest is the hybrid inverter, a licensed electrician, switchboard work, electrical certification, freight to the bottom of the world, and GST. None of those fall when cell prices do. Expect gradual reductions rather than the collapse panel prices went through.
There’s no battery rebate in New Zealand
Worth stating plainly, because people keep waiting for one. As of 2026 there’s no national subsidy for home battery storage comparable to Australia’s state schemes. Businesses and farms can claim GST input credits on a solar and battery install, but for a residential household the price you’re quoted is the price.
Backup value versus payback
Be clear with yourself about what you’re buying.
On payback alone, a battery is a weak investment at current New Zealand prices it typically extends a solar system’s payback by several years, and grid power at 30–38c/kWh isn’t expensive enough to close that gap quickly. Time-of-use plans improve the picture, but not dramatically.
Bought for backup, it’s a different product entirely. You’re buying a fridge that doesn’t defrost, a water supply that doesn’t stop, and for households with medical equipment or vulnerable family members something that isn’t measured in dollars at all. That’s a legitimate reason to buy, and it doesn’t need a payback calculation to justify it.
What doesn’t work is buying for backup and expecting payback economics to justify it afterwards.
Consents, rules and your lines company
Keep this short, because it’s your installer’s job to get right.
Battery systems above a certain size generally require building consent and electrical inspection, and installation has to meet distributed generation requirements including inverter compliance, isolation, switchboard configuration and backup circuit design. From 11 May 2026, a default maximum static export limit of 10 kW applies to many Part 1A distributed generation applications, unless your local distributor has a technically justified lower limit for your connection.
A good installer handles the consenting and the distributor application and tells you what applies to your address. If a quote is silent on consent and connection approval, ask before you sign.
Questions to ask before you sign
Take this list to any quote:
- Does this system provide backup during an outage, and how does it switch over?
- Which circuits will be backed up, and what will go dark?
- How long will it run those circuits on essentials only?
- What’s the continuous output and the surge rating? Will it start my water pump?
- What’s the usable capacity, not the nameplate figure?
- Can it recharge from my solar panels while the grid is down?
- Who handles a warranty claim, and is there support in New Zealand?
- Does this need building consent, and are you handling the distributor application?
If a salesperson is vague on questions 1, 4 or 6, that’s your answer. See what we install and how we size it at Cybotix Energy.
FAQs
Do solar panels work during a power cut in New Zealand?
Not on their own. Standard grid-tied systems shut down automatically for safety. You need a hybrid inverter with backup capability, dedicated backup circuits and a battery for your solar to keep working during an outage.
How long will a 10 kWh battery last in an outage?
On essentials fridge, lights, router, charging, at about 3–4 kWh a day roughly two to three days, which covers most New Zealand outages. Running a normal household load, expect closer to 8–12 hours.
Can I add a battery to my existing solar system?
Often yes, but it depends on your inverter. A standard grid-tied inverter usually needs replacing with a hybrid model, or an AC-coupled battery added. Get your existing setup assessed before assuming a simple retrofit.
Do I need consent for a home battery in New Zealand?
Systems above a certain size generally require building consent and electrical inspection, and the installation must meet distributed generation requirements. Your installer should confirm what applies and handle the process.
Is a battery or a generator better for outages?
A generator gives more output per dollar and runs as long as you have fuel. A battery is silent, fume-free, maintenance-light and recharges from your panels. For short and medium outages a battery is usually more practical; for extended heavy loads a generator still has a case.
How long do solar batteries last?
Generally ten years or more, though real service life depends on chemistry, temperature, depth of discharge and how hard it’s cycled. Warranty terms are a better guide than headline cycle-life claims.
Does a battery save me money on my power bill?
Some, by storing solar you’d otherwise export cheaply and using it in the evening. At current NZ prices it rarely pays for itself quickly which is why backup is the stronger reason to buy one.
The bottom line
Work in this order: confirm the system can actually provide backup, decide which circuits matter, size the capacity to your real outages, then check the output rating will start your heaviest load. Price comes last, because a cheaper system that doesn’t power your water pump hasn’t saved you anything.
And be honest about which product you’re buying. If it’s peace of mind during storms, that’s a good reason. If you’re expecting it to pay for itself, the numbers don’t support that yet in New Zealand.
