What Size Home Battery Do I Need? (2026 Guide + Sizer)

Q: Can I add more capacity later?

With modular systems yes - that's their main appeal. If the SA REPS incentive matters, expand before claiming, since it's once per premises.

Quick answer: Most South Australian homes land on a 10 to 13.5kWh battery – big enough to carry a family home through the evening peak, and inside the federal rebate’s full-rate band (first 14kWh). Smaller, quieter households suit 5 to 7kWh; large homes with heavy evening use or backup needs go bigger. The 60-second sizer below narrows it down for your situation.

What size battery do I need? – 4-question sizer

Your typical quarterly power bill Household size

Is someone usually home during the day? Do you want blackout backup?

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The honest rule of thumb

Size the battery to your evening and overnight usage, not your total usage. A battery earns its keep by covering the hours you’d otherwise buy peak-rate grid power. A typical SA family home uses 8 to 14kWh between late afternoon and morning – which is exactly why 10 to 13.5kWh batteries dominate installs here. Oversizing wastes capital on storage you rarely cycle; undersizing leaves you buying peak power every night.

Why the rebate makes 14kWh a magic number

The federal Cheaper Home Batteries Program pays its full rate (about $252 per usable kWh as of June 2026) on the first 14kWh, then drops to 60% of the rate up to 28kWh. So every kWh up to 14 is subsidised hardest – a 13.5kWh battery collects about $3,400 in federal rebate, while the 15th kWh onward earns much less per kWh. Unless you have unusually heavy usage, there’s rarely a reason to leap far past 14kWh on the first install.

Battery size	Federal rebate (approx.)	Suits
5-7 kWh	$1,260 – $1,760	Couples, low evening use, smaller homes
10 kWh	~$2,520	Most SA family homes
13.5 kWh	~$3,400	Bigger families, high evening use, backup
16-20 kWh	~$3,830 – $4,430	Large homes, EV charging at night, sheds/pumps

Federal rebate at ~$252/usable kWh to 14kWh, then 60% of rate to 28kWh. June 2026 figures.

~$252/kWh

Federal battery rebate

Cheaper Home Batteries Program - first 14kWh (≈$3,528 on a 14kWh battery). Steps down again at the start of 2027.

up to $2,050

SA REPS VPP incentive

For connecting your battery to an approved Virtual Power Plant. The amount scales with battery size and provider - typical 10-13.5kWh batteries attract roughly $600 to $1,000; the full $2,050 applies to larger systems, and concession households get around 30% more.

$1,000

City of Adelaide bonus

CBD postcodes only - most SA homes rely on the federal + VPP stack above.

Figures current as of June 2026. The SA Home Battery Scheme has closed. Source.

Common sizing mistakes

Sizing to your solar, not your usage. A big solar array doesn’t mean you need a big battery – the battery should match what you consume after dark.
Ignoring the EV question. If an electric car is in your 5-year plan, mention it – overnight charging changes the maths and may justify going bigger now or choosing a modular battery you can stack later.
Paying for backup you didn’t ask about. Whole-home backup needs extra hardware. If you only want the fridge, lights and wifi protected, an essentials circuit is cheaper.
Forgetting the VPP. Joining a Virtual Power Plant unlocks the SA REPS incentive, and some VPPs work better with certain sizes and brands – compare SA VPPs here.

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Battery sizing FAQs

What size battery do I need for a typical SA home?

Most SA family homes suit a 10 to 13.5kWh battery – enough to cover evening and overnight usage, and inside the federal rebate’s full-rate band. Smaller households with modest bills suit 5 to 7kWh.

Is a bigger battery always better?

No. Beyond your overnight usage, extra capacity rarely gets cycled, and the federal rebate rate drops to 60% past 14kWh. Size to your evening usage, and go modular if you might expand later.

What size battery do I need to run an air conditioner overnight?

A reverse-cycle unit cooling one zone draws roughly 1 to 2.5kW. Running it for a few evening hours plus normal household load is comfortably inside a 10 to 13.5kWh battery. Whole-home ducted cooling all night needs more – tell your installer that’s the goal.

Can I add more capacity later?

With modular systems (BYD, Sigenergy, Powerwall 3 with expansion units) yes – that’s their main appeal. Fixed batteries can be paired with a second unit but it’s less elegant. If REPS matters, claim once: expand before claiming, since the incentive is once per premises.