Guide - Updated July 2026
What size solar battery do you need in Australia?
Most homes land between about 8 and 13.5 kWh usable. This guide explains how evening load, solar size and backup goals change that answer - and when 20 kWh is overkill.
Start with evening electricity, not the brochure
A home battery mainly shifts daytime solar into the evening and overnight. The right size is therefore driven by how many kilowatt-hours you import after sunset, not by the largest marketing number on a product sheet.
If your household uses about 8 to 12 kWh between late afternoon and morning, a 10 to 13.5 kWh usable battery often covers a large share of that load once solar has charged it. If evenings are lighter - for example a small home with efficient appliances - 8 kWh can be enough. Heavy evening cooking, heating, EV charging at home, or large families push the range upward.
Common Australian size bands
Product lines cluster around familiar usable capacities. Treat these as planning bands, not prescriptions:
- Around 8 kWh: smaller homes, lower evening use, or a first step into storage
- Around 10 kWh: a very common sweet spot for many suburban households
- Around 13.5 kWh: higher evening use or wanting more nights covered without upsizing to 20
- Around 20 kWh: large homes, bigger solar arrays, or stronger backup ambitions - check taper and payback carefully
Match the battery to your solar
A battery that never fills is wasted capital. If you have a modest 5 to 6.6 kW solar system and cloudy winters, a 20 kWh battery may sit half empty for much of the year. Conversely, a large north-facing array that exports a lot of daytime energy can justify more storage - as long as evening demand exists to discharge into.
Also check inverter limits. Some hybrid inverters cap charge and discharge power (kW). A big battery that can only charge slowly may not refill on short winter days, which hurts both self-consumption and backup readiness.
Backup is a different design problem
Backup during an outage depends on which circuits are covered, continuous and surge power limits, and how long you need critical loads to run. A battery sized perfectly for bill savings can still be too small - or wrongly configured - for whole-home backup.
Decide early whether you want bill optimisation only, essential-circuits backup, or something closer to whole-home resilience. That choice often matters more than picking 13.5 versus 16 kWh on paper.
When bigger stops helping
Federal rebate taper means the last kilowatt-hours of a large pack get less subsidy support per kWh than the first 14. If those extra kWh only cover rare high-use nights, payback can stretch out.
Use our calculator in size and payback modes, then compare quotes for two neighbouring sizes (for example 10 vs 13.5 kWh). Choose the smaller one if the larger pack only shaves a little more grid import for a lot more capital.
Run the numbers for your home
Use the free calculator for size, net cost after rebates, savings and payback - no email required. Or browse typical prices in the solar battery cost guide.
FAQs
Is 10 kWh enough for most Australian homes?
Often yes for bill-focused installs with typical evening use and a mid-size solar system. Homes with high night loads, EVs or strong backup goals may need more.
Should I size for 100% self-sufficiency?
Usually no. Designing for every winter evening can force an oversized battery. Many households aim to cut evening imports materially rather than eliminate the grid.
Does usable kWh or branded kWh matter?
Usable (or usable energy) is what you can actually cycle. Always compare usable figures when reading quotes.