A home battery stores electricity for later use. In an Australian solar home, that normally means charging from surplus rooftop solar during the day and discharging in the evening or during higher-price periods.
What size home battery do you need?
There is no universal “best” capacity. A useful starting point is the amount of electricity you normally use outside solar-production hours, then adjust for battery depth of discharge, efficiency, backup requirements and future loads such as an EV.
Estimate a battery size from your daily usage →
Common capacities
Australian residential systems commonly span from smaller units around 5–10 kWh to larger 20 kWh-plus installations. The right size depends on usage, not marketing labels.
- Smaller battery: can suit lower evening usage or a household focused on partial bill reduction.
- Mid-size battery: may suit households with higher evening loads or more surplus solar.
- Larger battery: can be useful for high consumption, multiple dwellings, large solar arrays or substantial backup needs, but oversizing can reduce utilisation.
Usable capacity matters more than headline capacity
Compare the energy the manufacturer allows you to use, not just the nominal number printed in the product name. Also compare continuous output power, surge capability, efficiency, warranty throughput and backup behaviour.
What determines battery savings?
The main value usually comes from avoiding grid imports. If you would otherwise export solar for a low feed-in tariff and later import power at a much higher rate, storing that solar can create value. Time-of-use tariffs can make the timing of charging and discharging even more important.
Use the Battery Payback Calculator with your own tariff and installed cost.
Federal battery support
Eligible Australian battery installations may receive support through the Cheaper Home Batteries Program. From 1 May 2026, the STC support is tiered by usable capacity, with full factor support to 14 kWh, reduced support from above 14–28 kWh and lower support from above 28–50 kWh.
Estimate the certificate entitlement with the Battery Rebate Calculator.
Backup is not automatic
A battery does not necessarily power your home during a blackout just because it is installed. Backup requires compatible equipment and an installation configuration designed for islanded operation. Some systems back up selected circuits; others can support more of the home depending on inverter power and installation design.
Five figures to compare on every quote
- Usable kWh.
- Continuous kW output.
- Installed price after applicable discounts.
- Warranty years and throughput conditions.
- Expected annual value using your own tariff and usage.
Do not buy solely on rebate size. The best-value battery is generally the one that matches the energy profile it is expected to serve.