The best home battery size is based on the electricity you want to use after solar generation falls, the surplus solar available to charge the battery and the power needed by your appliances. A larger battery is not automatically the best-value option.
Understand kWh and kW
Battery capacity is measured in kilowatt-hours (kWh) and describes how much energy can be stored. Power output is measured in kilowatts (kW) and describes how much power the battery can deliver at a given time. Both matter: capacity affects how long energy may be available, while power output affects which appliances can run together.
Use your evening consumption
Look at interval data to estimate how much electricity your household uses after sunset. Consider cooking, hot water, air-conditioning, pool pumps and EV charging. Your daily average is useful, but seasonal and weekday/weekend patterns can also matter.
Consider the solar surplus
A battery needs energy to charge. Review how much excess solar is normally exported and whether the solar system can charge the battery on typical days. Winter generation, shading and household daytime usage can change the result.
Decide whether backup is important
Backup during a blackout requires compatible equipment and selected circuits to be configured for backup. Ask about continuous and peak output, essential-load circuits and whether the system can start and operate without the grid.
Get a system-specific assessment
Compare usable capacity, power output, warranty terms, inverter compatibility and the exact battery model. A proposal should explain expected energy benefits and savings assumptions. Visit our Brisbane battery storage page for more information.