What size home battery do you need? 16kWh vs 24kWh vs 32kWh vs 40kWh

Sizing a battery is a different exercise from sizing solar. With panels you're matching total daily usage — see what size solar system do you actually need for that. With a battery you're matching something narrower: how much power you use after the sun goes down.

Start with your evening usage, not your total

A battery's job is to carry you from late afternoon through to the next morning. Daytime load is covered by the panels directly. So the number you actually want is your overnight consumption, not your 24-hour total.

A rough way to get at it from a bill: take your total kWh for the billing period, divide by the days to get kWh/day, then assume somewhere around a third to a half of it happens outside daylight hours for a typical household. If you run ducted air conditioning in the evening, have a pool pump on a timer, or charge an EV overnight, your share will sit well above that.

The four sizes we install

• 16kWh — $8,900 installed. The standard choice for a small-to-average household. Comfortably covers an evening of lights, fridge, TV, cooking and a normal run of appliances for 1–3 people.
• 24kWh — $11,900 installed. A family home with real evening load — dinner, dishwasher, a few hours of air conditioning after dark. This is also the size where the refer-a-friend discount kicks in: if you and a friend both install 24kWh or more at the same time, you each get $300 off.
• 32kWh — $14,900 installed. Large family homes running ducted A/C after dark, a pool, or a workshop. Also the minimum we'd put with a 17kW solar system.
• 40kWh — $17,900 installed. Large modern homes with heavy evening load, or anyone who wants genuine multi-day resilience rather than just overnight cover.

All four are the same modular GoodWe ESA range, built from 5kWh and 8kWh blocks, so the physical install is the same job at every size.

The rebate quirk worth knowing before you choose

The federal battery rebate doesn't pay a flat rate across the whole battery. Since May 2026 the first 14kWh earns the full certificate rate, 14–28kWh earns 60% of it, and 28–50kWh earns 15%.

That has a practical consequence: the first 14kWh of any battery is the best-subsidised part of it. Going from 16kWh to 40kWh more than doubles the price but does not come close to doubling the rebate. Bigger is still bigger — it just isn't a linear bargain, and anyone comparing two differently-sized quotes should know that's why the discount percentages don't match.

You don't have to decide forever today

The GoodWe ESA range is modular, so starting at 16kWh and adding blocks later is a genuine option rather than a sales line. If budget is the constraint, a smaller battery now that you extend in a couple of years is a perfectly sensible path — and it means you're not guessing at what your usage will look like after you've added an EV or a pool.

The one place we don't leave it open: at 17kW of solar we require at least 32kWh of storage, because generation that high needs somewhere to go.

Get it sized properly

Our Quote Builder now lets you pick the capacity yourself and shows the price update live, with a suggested size based on your usage band. Or call Brooke on 0408 258 298 and we'll work it out off a recent bill — that beats guessing every time.