If you’re looking at battery storage for your home, one of the first questions is usually:
“What size battery do I actually need?”
And the honest answer is — it depends.
Not every home needs a massive battery, and not every home will get enough value from a smaller one. The right battery size comes down to how much electricity you use, when you use it, what size solar system you have, and what you want the battery to do.
For some homes, a 5kWh battery is enough to cover light evening usage. For others, especially homes with EVs, pools, ducted air con or all-electric appliances, a 20kWh or even 40kWh+ setup can make much more sense.
A simple guide to battery sizes
5kWh battery
A smaller battery suited to:
- low energy households
- couples or smaller homes
- light evening usage
- basic backup for essentials
Good if you want a simple entry into battery storage, but it can feel limited in larger homes.
10kWh battery
This is often the sweet spot for many homes.
A 10kWh battery is a good fit for:
- average family homes
- homes with a 6.6kW solar system
- households wanting better evening coverage
- homeowners wanting a balance of savings and backup
For many households, this is where battery storage starts to make a noticeable difference.
15–20kWh battery
A stronger option for:
- larger family homes
- higher evening usage
- all-electric homes
- homes wanting better backup coverage
- households with one EV
This range gives you more comfort overnight and usually feels like a more complete battery setup.
20–30kWh battery
This is where battery storage starts suiting:
- larger homes
- pool or spa homes
- heavy air con use
- stronger blackout backup
- bigger solar systems
- homes with EV charging
If your home uses a lot of power after sunset, this range often makes more sense than a standard 10kWh system.
40kWh+ battery
This is for high-consumption homes.
Usually suited to:
- multiple EVs
- large homes
- all-electric households
- ducted air con
- pools, spas and larger appliance loads
- homeowners wanting serious backup and strong energy independence
For the right home, 40kWh+ isn’t oversized — it’s just properly matched.
What actually decides the right battery size?
The best battery size usually comes down to these 4 things:
1. Your daily electricity usage
The more power you use, the more storage you may need.
2. When you use your power
If most of your usage is in the evening, a battery becomes much more valuable.
3. Your solar system size
A battery works best when there’s enough excess solar to charge it during the day.
4. Your backup expectations
Do you just want to keep essentials running, or do you want stronger backup across more of the home?
So what size battery do most homes need?
As a rough guide:
- Small home / low usage → 5–10kWh
- Typical family home → 10–15kWh
- Larger family / higher usage → 15–20kWh
- All-electric / EV / larger home → 20–30kWh
- High-demand / multiple EV / premium setup → 40kWh+
Final thoughts
The best battery isn’t always the biggest one.
It’s the one that matches:
- how your home uses power
- how much solar you have
- what you want backed up
- and whether you have larger loads like EVs, pools, or ducted air con
If you’re unsure whether your home needs 10kWh, 20kWh or 40kWh+, the best approach is to size the battery around your actual usage, not just what someone else has installed.
Need help choosing the right battery size?
At Empower Solar Australia, we help homeowners choose the right battery setup based on real household usage, solar production, backup needs and future energy plans.
