What Size Solar Battery Is Actually Worth It

If a neighbour has just put in a large home solar and battery setup, it is natural to wonder whether you should match them and buy a bigger solar battery too. Before you do, know that the maths that used to reward a bigger battery changed on 1 May 2026. Going large is no longer the automatic win it once was.

The right size comes down to your home, not the one next door. A pool pump running overnight, ducted air conditioning most summer evenings, or an electric car on the horizon each pull your ideal battery size in a different direction, which is why the very same battery can be spot on for one house and money wasted at the one next door.

What changed on 1 May 2026

For a while, a bigger battery meant a bigger rebate, so there was a natural pull towards buying the largest system you could. That is no longer how the solar battery rebate works.

On 1 May 2026 the Cheaper Home Batteries Program from the Federal Government changed in two ways that matter for sizing. First, the amount you get for each kWh dropped by about 19 percent (the rate behind it moved from 8.4 to 6.8). Second, and more importantly, the solar battery rebate is now weighted toward normal household sizes: you get the full amount on usable storage up to around 14 kWh, and noticeably less above that, up to a cap of 50 kWh.

In plain terms, once your battery goes past about 14 kWh, each extra kWh earns a smaller rebate, and past the mid twenties there is almost none left. The old idea of buying big to claim a big solar battery rebate no longer holds, and the rate is set to step down again from 2027.

So what size is the sweet spot? For most homes, 10 to 14 kWh

The part a battery actually needs to cover is the evening and overnight stretch, from sunset to the next morning, since your rooftop home solar feeds the house directly during the day.

For the average home using around 16 kWh a day, that evening load usually sits around 10 to 14 kWh. Pair it with a common 6.6kW solar system making roughly 24 to 27 kWh on a good day, and a solar battery of about 10 to 13 kWh captures most of the surplus solar you would otherwise export for very little. It sits inside the full rebate band, which is exactly where a home solar and battery setup gives the best value, and it keeps the solar batteries price sensible because you are not paying for capacity you rarely use. That 10 to 14 kWh range fits most homes, but the right number really depends on what you run. As a rough guide:

• Low use home (1 to 2 people, out by day): 8 to 11 kWh
• Busy family home (3 to 4 people): 10 to 14 kWh
• Home with an EV (3 to 4 people, evening charging): 16 to 22 kWh
• High load home (pool, ducted air con, WFH, EV): 25 kWh and up

Whichever profile you land in, going bigger than you need backfires. Your home solar may not fully charge an oversized solar battery, especially in winter, and your evening use may not drain it, so it sits half full most nights doing nothing for your bill. That is overspending, not saving.

A solar battery earns its keep when you can fill it and empty it most days. One number to check: usable capacity is less than the figure on the brochure (a 13.5 kWh unit often delivers about 12 kWh), and batteries for solar lose a little capacity each year, so size around what you can really use and leave a small buffer.

Not sure? Let's size it together

Bigger no longer means better value, and the right number comes down to your home, not the system next door. The quickest way to land on it is a free consultation, where we size the solar battery to your actual usage and check the solar battery rebate you qualify for. It helps to have a few things in mind:

• A recent electricity bill, or a sense of how much you use after dark. That evening load is what the battery covers.
• Your home solar setup or plans for it, for example a 6.6kW solar system, since panel size caps how much you can store. Most batteries for solar are modular, so you can start sensibly and add later.
• What is on the horizon (an EV, a pool, a move away from gas) and what matters most: lower bills, blackout backup, or getting the most out of your solar. Flag any must-run needs like medical equipment so backup is planned, not assumed.

With that, we can put two or three solar battery designs at different sizes in front of you, each with its own price, so you can compare the solar batteries price at each size and see exactly what suits your home.