What Size Battery Do I Need for My Home?

Where do we start?

With your bill. It shows how much power you use a day and, on many plans, when you use it. If you have solar, your inverter app shows how much you export. Those two numbers drive the size.

What is our sizing rule?

We size a battery to cover about one full day of your expected use, and up to about one and a half times that where usage and budget support it. We recommend the smallest size that covers the first figure, and show the next size up as an option if your household is growing, adding an EV or electrifying.

Why not just go big?

A battery only earns its keep when it charges and discharges. If it is much bigger than your evening use, part of it sits idle. If your solar can't fill it, the extra capacity rarely gets used. Bigger also changes the rebate: the federal discount tapers as usable capacity rises.

What else changes the size?

• Solar surplus. The battery needs spare solar to fill it.
• Backup. If you want long blackout cover, you may choose more capacity.
• Big evening loads. Ducted air conditioning, pool pumps, cooking and EV charging after dark.
• Time-of-use pricing. An expensive evening peak makes covering it more valuable.
• Power rating. Make sure the battery can deliver enough power at once, not just enough energy.

What about the cost?

Home batteries start from the range on our battery prices page, after rebates and including GST. Your fixed quote follows a site inspection.

A real example

We installed a 27.99 kWh AlphaESS SMILE-M5 battery in Heathcote. The size followed the household's daily use and solar surplus, the same way we size every battery.

Want us to size it?

Request a proposal with a recent bill. We will recommend a size, show the step up, and explain why.