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.

SA REPS VPP incentive – current status (August 2026): general-household funding was fully allocated in May 2026. For the remainder of 2026 the REPS VPP incentive is open to priority group households only – up to $1,030 on a 13kWh battery and up to $2,050 on a 28kWh system. Further funding is expected early 2027. The federal rebate below is unaffected and open to all households. Check if you qualify as a priority household.

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.

Priority
households only

SA REPS VPP incentive

For connecting your battery to an approved Virtual Power Plant. General funding was exhausted in May 2026; until further funding arrives (expected early 2027) it is open to priority households only - up to $1,030 on a 13kWh battery, up to $2,050 at 28kWh.

$1,000

City of Adelaide bonus

CBD postcodes only - most SA homes rely on the federal rebate above.

SA REPS VPP incentive - current status (August 2026): general-household funding was fully allocated in May 2026. For the remainder of 2026 the REPS VPP incentive is open to priority group households only - up to $1,030 on a 13kWh battery and up to $2,050 on a 28kWh system. Further funding is expected early 2027. The federal rebate below is unaffected and open to all households. Check if you qualify as a priority household.

Figures current as of August 2026. The SA Home Battery Scheme (the old state subsidy) closed in 2022 and has not been replaced. Federal source · REPS status 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 is the route to the SA REPS incentive (priority-group households only for the rest of 2026), 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.