As solar adoption grows rapidly across Australia, more homeowners are considering solar battery storage to gain energy independence and reduce power bills. One of the most critical decisions when installing a battery is choosing the right size. Whether you’re just starting or upgrading an existing system, selecting between 5kWh, 10kWh, or larger capacities can dramatically affect your system’s performance, payback time, and long-term savings.
In this comprehensive guide, we help you evaluate which battery size suits your energy consumption, budget, and lifestyle.
Why Battery Size Matters
Choosing the correct solar battery size is more than just guessing how much electricity you use. Battery size impacts:
- How much solar energy you can store and use later
- How much grid electricity you avoid using during peak times
- Whether your system qualifies for government rebates or VPPs
- The overall cost and return on investment (ROI)
For example, a 5kWh battery may be suitable for minimal use and backup only, while a 13kWh system may allow you to power your home through the night.
Key Factors to Consider Before Choosing a Size
Your Daily Energy Consumption
Review your electricity bills or use monitoring apps to determine average daily and nighttime usage. A household consuming 15–20kWh/day with evening peaks will need a larger battery.
Your Solar System Output
A 6.6kW solar panel system can produce ~24–30kWh/day in good conditions. If you’re exporting a large portion of that energy to the grid, a battery can help store it for evening use.
Your Usage Pattern
- Work-from-home families may use energy throughout the day.
- EV owners need charging capacity overnight.
- Night-time heavy users will benefit more from larger batteries.
Grid Tariffs
If you’re on a time-of-use tariff, battery storage helps avoid expensive peak hour rates.
Backup Requirements
A 5kWh system may keep your fridge and lights running, but won’t power your air con or induction cooktop during outages.
Common Battery Sizes Compared
| Battery Size | Ideal For | Avg Cost (Installed) | Backup Power | Pros | Cons |
| 5kWh | Small homes or backup only | ~$3,000–$5,000 | Basic | Affordable entry-level size | Limited storage, not futureproof |
| 10kWh | Standard family homes (3–4 people) | ~$4,000–$10,000 | Moderate | Balanced value & performance | May not be enough for EV use |
| 13–20kWh+ | Large homes, EV owners, off-grid | $10,000+ | Full | Long-term savings, future-ready capacity | Higher upfront cost |
How to Estimate Your Battery Needs
Step 1: Measure Your Night-time Usage
Check how much electricity you use after 5PM. This is when your solar panels stop producing, and you rely on stored energy.
Step 2: Apply Usage to Battery Sizing
- 5kWh battery ≈ powers lights, fridge, WiFi & some TV
- 10kWh battery ≈ adds dishwashers, washing machines
- 15–20kWh ≈ includes EV charging or full backup
Step 3: Leave Headroom
Battery DoD (Depth of Discharge) means you rarely use 100% of capacity. For example, a 10kWh battery with 90% DoD = 9kWh usable.
Step 4: Future-Proof Your System
If you plan to add an EV or work from home, consider a stackable battery that lets you scale over time.
FAQs: Choosing Solar Battery Sizes in Australia
10kWh is the most popular size, suitable for 3–4 person households and general backup.
Not necessarily. Oversized systems lead to underutilisation and longer payback. Choose based on your real usage data.
Yes—many systems today are modular or stackable, letting you add more capacity later as your needs grow.
Absolutely. Brands like AlphaESS, Swatten, and Deye offer multiple sizes (e.g., 5kWh–20kWh), flexible integration, and longer warranties.
Evening-heavy use = larger battery. Daytime-heavy use = smaller battery may suffice. Tailor size to avoid energy waste or shortages.
Solar Rains offers scalable battery systems from AlphaESS, Swatten, Deye, and Dyness, available for residential & commercial needs.
Conclusion
Choosing the right solar battery size is a balancing act between cost, usage, and future scalability. Whether you’re looking for a small 5kWh backup or a robust 15kWh full-home storage system, the key is to evaluate your energy needs carefully.
Need expert advice? Solar Rains supplies wholesale solar products & battery systems tailored to Aussie homes. Contact us to match your lifestyle with the perfect energy storage solution.
