Is a 13-14kWh battery right for your home?
The 13-14kWh range has become a common battery size, but whether it suits your home depends on your specific circumstances. Here are the factors involved.
Short answer
Batteries this size have become popular because they often suit medium-sized households with moderate solar systems. But popular doesn't mean right for everyone: it comes down to your evening and overnight usage, your solar system size and your goals.
- Usable capacity
- 13.5kWh
- Typically what the label means: the energy you can draw. The total can be higher, e.g. 14.4kWh
- Light load, 500W
- 26+hours
- Theoretical, from a full 13kWh battery
- Heavy load, 3kW
- About 4hours
- Theoretical, from a full 13kWh battery
- Price
- Varies
- Similar capacity systems can differ by thousands of dollars
Pricing varies significantly
On this page6 sections
Understanding battery capacity
When you see "13.5kWh" on a battery specification, that typically refers to the usable capacity: the energy you can actually draw from the battery.
The usable capacity may differ from the total because batteries are designed not to fully discharge, which protects their longevity. A battery marketed as 13.5kWh might have a 14.4kWh total capacity with 13.5kWh usable, or it might already be stating the usable figure.
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What affects how much battery you need?
Battery sizing isn't one-size-fits-all. Your ideal capacity depends on several interconnected factors.
Your evening and overnight usage
A home battery usually stores solar energy from the day for the evening and overnight. When you cook, run appliances, watch TV and use heating or cooling largely determines how much storage you need.
A household that uses most of its energy before 4pm needs something different from one where everyone comes home at 6pm and runs several appliances at once. Look at your bills or smart meter data rather than relying on averages.
Your solar system size
A battery needs solar energy to charge. If your system barely covers your daytime usage, there may not be much excess to store. A very large system might justify a larger battery to capture more of that excess.
The relationship isn't linear. A bigger battery doesn't automatically mean more savings if your solar can't fill it, or if your evenings don't need that much stored energy.
Your goals and priorities
Different goals lead to different sizing decisions.
| Your goal | How you might size |
|---|---|
| Maximising self-consumption | Cover most evening usage, accepting that some solar export still happens on high-generation days |
| Backup power priority | A larger battery for longer backup during outages, even if it doesn't fill every day |
| Budget constraints | A smaller battery covering your core evening needs might be better value than a larger one that's rarely fully utilised |
The 13-14kWh range: how long it lasts
Fully charged, a battery this size holds enough energy to run typical evening loads for many hours. What you're running decides how many.
Theoretical, from a full 13kWh battery. Real-world usage falls somewhere in between, with periods of higher draw (cooking, heating and cooling) and lower draw (overnight, with just the fridge and standby loads). Your actual experience will differ from any theoretical calculation.
Questions to discuss with your installer
Key questions before you commit.
Before you commit
6 questionsSynergy tariff considerations
Your electricity tariff affects battery economics.
Where the value comes from
Under Synergy's Distributed Energy Buyback Scheme (DEBS), export rates vary by time of day. The difference between what you'd earn exporting and what you'd pay importing creates the value of stored energy.
That value changes if
- Synergy adjusts tariffs
- You change your usage patterns
- You make other changes to your home, like adding an EV or pool
A battery sized perfectly for today's circumstances might be over or under-sized for tomorrow's.
A note on rankings
Next steps
If you're considering a battery in this size range, we recommend:
Gather your data
Get at least 12 months of electricity bills, or access your smart meter data through Synergy's online portal.Understand your patterns
When do you use the most electricity? What are your peak loads?Get multiple quotes
Talk to several installers, and pay attention to those who ask detailed questions about your situation before recommending a size.Compare apples to apples
Make sure quotes include the same components and services so you can compare them fairly.
See which batteries fit your usage
Want to take the next step?
Get a quote from an installer from our network that covers your area. You choose whether to act on it. No obligation.