What Size Home Battery Do I Need? Getting the Most From the 2026 Rebate

Short answer: for most Australian homes in 2026, a battery with 10 to 14 kWh of usable capacity is the sweet spot. That is where the federal rebate pays its full rate, and it covers a typical household's evening and overnight use. Going bigger costs more per kWh because the rebate shrinks above 14 kWh.

Why 14 kWh is the magic number

Since 1 May 2026 the Cheaper Home Batteries rebate is tiered by size (Clean Energy Regulator):

At roughly $250 per kWh for May to December 2026 (SolarQuotes), that means approximately:

• 10 kWh: about $2,400 off
• 14 kWh: about $3,400 off
• 20 kWh: about $4,300 off. The extra 6 kWh earns only around $900 more rebate.
• 30 kWh: about $5,500 off

Every kWh above 14 costs you noticeably more after the rebate. Only buy that extra capacity if you will genuinely use it.

Step 1: Find your evening and overnight use

A battery's job is to cover the power you buy after the sun goes down. Look at your smart meter data in your retailer's app or portal, and add up a typical day's use from about 5pm to 7am. Many households land between 6 and 12 kWh; SolarQuotes' payback modelling assumes about 7 kWh. Air-conditioning, electric heating, cooking and an EV charging overnight push this higher.

Step 2: Check you have enough spare solar to fill it

A battery only saves money if your panels can charge it. On an average day you need enough solar left over, after your daytime use, to fill the battery. As a rough guide, a 10 kWh battery suits a solar system of about 6.6 kW or more. In winter, with shorter days, many batteries won't fill completely.

Step 3: Take the smaller number

Your useful battery size is the smaller of your evening use and your spare solar. Extra capacity beyond that sits empty and adds cost without adding savings. Our home battery size calculator does this for you. Enter your usage and solar size and it rounds up to a common battery size.

When a bigger battery does make sense

• You charge an EV overnight and have a large solar system, of 10 kW or more.
• You want whole-home blackout backup for long outages, for example in a rural or storm-prone area.
• You are joining a virtual power plant that pays well for capacity.
• You plan to electrify: a heat pump, induction cooking or an EV in the next couple of years.

Usable vs total capacity

Always compare usable kWh. A battery sold as "13.5 kWh" may have more total cells but less usable energy. The rebate is also based on usable capacity, up to 50 kWh (CHOICE). Check the spec sheet, not the brochure headline.

Worked example

A Sydney household uses 9 kWh between 5pm and 7am and has a 6.6 kW solar system that exports about 15 kWh on a typical day. Their spare solar (15 kWh) is more than their evening use (9 kWh), so evening use is the limit. A battery of about 10 kWh usable covers it, with a little headroom for cloudy days and battery ageing. A 20 kWh battery would cost thousands more and sit half empty most nights.

Bottom line

Size your battery to your evening use, check your solar can fill it, and stay at or under 14 kWh unless you have a clear reason not to. Then get three quotes and compare the price per usable kWh after the rebate. Our guide Is my battery quote fair? shows you how.

Figures checked November 2026. The rebate rate drops every six months; confirm the current figure with your installer.