What a battery actually does for you
Solar without storage sends your surplus to the grid for a feed-in rate that is well below what you pay to buy power back at night. A battery closes that gap: you store the cheap daytime energy and use it in the evening peak instead of buying it.
That means the value of a battery depends almost entirely on the gap between your feed-in tariff and your usage rate, plus how much surplus you're currently exporting. If you already use most of your solar during the day, a battery adds less.
Blackout backup is a separate feature
Not every battery keeps your house running in an outage, and not every install wires it up that way. Backup requires a changeover device and a nominated backup circuit — it's a design decision made before installation, not a setting flicked on later.
On the Sunshine Coast this matters. Storm season outages are the reason a lot of our customers finally pull the trigger on storage, particularly on properties with a bore, septic pump or medical equipment.
If backup matters to you, say so up front, and decide which circuits you want kept alive: usually fridge, lights, internet, a few power points, and sometimes one air-conditioner.
How to compare batteries
- Usable capacity (kWh), not just nominal capacity — they're different numbers.
- Continuous power output (kW) — this decides what you can run at once off the battery.
- Whether backup is supported, and what it costs to wire in.
- Warranty terms: years, throughput, and guaranteed retained capacity at end of term.
- Whether it's AC-coupled onto an existing system or a hybrid inverter replacement.
- Scalability — can you add a second module later without replacing the lot?
- Where the manufacturer's support presence is, because a warranty is only as good as the company behind it.
Sizing a battery
The usual approach is to look at your evening and overnight consumption — the power you draw after the sun goes down — and size the battery to cover most of it, rather than sizing it to your total daily usage.
Oversizing a battery relative to your surplus solar means paying for capacity that never fills. Undersizing means you're back on the grid by 9pm. Your interval data (available from your retailer) makes this a precise exercise rather than a guess.
We install Sigenergy, Sungrow and GoodWe storage and will tell you plainly if we think a battery won't pay for itself on your usage pattern.
Common questions
Can I add a battery to an existing solar system?
Usually yes. Depending on your inverter, it's either AC-coupled alongside it or the inverter is replaced with a hybrid unit. We'll check what you have and tell you which is better value.
Will a battery power my whole house in a blackout?
Only if it's designed and wired for backup, and only up to its power output. Most setups run nominated essential circuits rather than everything at once.
How long do home batteries last?
Manufacturers typically warrant them for a set number of years or a total energy throughput, with a guaranteed remaining capacity at the end. Compare those three figures side by side.
Want this checked against your own bill?
We'll give you a system size, price and payback estimate for your actual roof and usage.