Straight answers, 2026
What size battery do I need?
The short answer
To lower your bill, a battery a little under your daily usage is the usual fit. A home using 15 kWh a day suits about 14 kWh of storage, and a home using 25 kWh a day suits about 22 kWh. Backup for blackouts needs a much bigger battery.
Sizing method as used by Ray, our solar advisor. Prices as at 21 August 2026, after the federal discount. By Verified Solar. Last updated .
It depends on what you want the battery for
The right size changes a lot with the job you want it to do. Decide that first, because the same home can need 14 kWh for one goal and more than double for another.
- Lowering your bill: store daytime solar and use it in the evening and overnight.
- Backup in a blackout: keep the home running for a day or two without the grid.
- Joining a virtual power plant: extra capacity the retailer can draw on, on top of what your home uses.
Sizing a battery to lower your bill
Most of a battery's work is covering the evening and overnight. Ray sizes it at about 80 percent of your daily usage, plus 10 percent to allow for wear and the charge a battery always keeps in reserve.
| Daily usage on your bill | Battery size and price |
|---|---|
| 15 kWh a day | about 14 kWh, $10,700 to $13,650 |
| 25 kWh a day | about 22 kWh, $10,700 to $13,650 |
| 35 kWh a day | about 31 kWh, $13,650 to $17,450 |
Sizing a battery for blackouts
Backup means covering the whole home, day and night, without the grid. The usual target is two full days, which takes a little over twice your daily usage. A home using 15 kWh a day needs about 33 kWh, roughly $16,650 to $21,250 installed.
Sizing for a virtual power plant
If you plan to join a virtual power plant, allow extra capacity on top of your own usage so the retailer can draw on it without leaving you short. Ray adds about 15 kWh for this.
Get the size right the first time
The federal Cheaper Home Batteries discount can only be claimed once per property, and it covers storage up to 50 kWh. Spend it on a battery that is too small and adding more later means paying full price, often with the labour and switchboard work paid twice. That makes the size decision worth more care than it looks.
Common questions
Is a 10 kWh battery enough?
For lowering the bill it suits a home using about 11 kWh a day. Many homes use more than that, so check the daily usage on your bill first.
Do I need solar panels to get a battery?
A battery works best with solar, because it stores your own daytime power for the evening and overnight. Ray sizes the two together from your bill.
Can I add more battery later?
Often, yes, but the federal discount can only be claimed once per property, so extra storage added later is usually paid at full price.
Get the answer for your home
Tell Ray your bill and what you are after. He sizes the system and explains the rebates before anyone quotes you. Free, and no details needed to start.