June 25, 2025

What Size Solar Battery Do I Need? Australian Homeowner’s Guide

Choosing the right solar battery size is essential for Australian homeowners who want to fully utilise their solar investments. With the rise of solar battery storage, homeowners can save on electricity bills, achieve energy independence, and better prepare for power outages.

This guide will help you understand recommended battery sizes for common solar systems, factors that influence your choice, and how to accurately determine the best setup.

How Big of a Solar Battery Do I Need?

To estimate the right battery size, consider your daily energy usage and desired backup duration. Use this table as a guideline:

Solar System Size	Typical Household Use	Recommended Battery Capacity
6.6kW	20–25kWh/day	8–12kWh (daytime load)
10KW	30–40kWh/day	12–16kWh (cover evening use)
13KW	50–60kWh/day	16–20kWh (full-home backup)

 

What Size Battery Do You Need for My Solar System?

The ideal battery size depends largely on the capacity of your solar panel system and your household’s daily energy habits. To simplify the decision, we’ve broken down common solar system sizes in Australia - 6.6kW, 10kW, and 13kW - along with recommended battery capacities for each.

These guidelines can help you match your system’s output with a suitable storage solution, ensuring you get the most out of your solar investment.

1. For a 6.6kW System

A 6.6kW solar system typically generates approximately 24–27kWh per day, depending on your location, roof orientation, and seasonal sunlight variations. This size is ideal for small to medium-sized households with average daily electricity needs.

Recommended battery size: 8–12kWh usable capacity

Pairing a 6.6kW system with an 8–12kWh battery allows you to capture excess daytime solar and use it during high-demand periods in the evening.

It’s an excellent setup for reducing reliance on the grid, lowering energy bills, and gaining some independence from time-of-use tariffs.

For homes looking to store enough power for essential appliances like lighting, fans, Wi-Fi, and small kitchen appliances, this range offers a balanced mix of affordability and functionality.

2. For a 10kW System

A 10kW solar system produces around 38–44kWh per day, which is suitable for larger households, families with high daytime usage, or homes with electric vehicles or air conditioning.

Recommended solar system battery storage: 12–16kWh usable capacity

This battery size enables homeowners to store enough energy for evening use, manage peak-time loads, and even maintain limited backup during grid outages.

With this setup, households can significantly reduce electricity bills, especially when paired with smart energy management systems. It also provides an efficient cushion against energy price volatility, making it a popular choice among future-proof homeowners.

3. For a 13kW System

A 13kW solar system can output between 50–55kWh daily, making it ideal for energy-intensive households, multi-generational families, or homes running multiple high-consumption appliances.

Recommended solar system battery storage: 16–20kWh usable capacity

This capacity allows for full home usage overnight, supports extended off-grid operation, and delivers robust protection against blackouts. It also suits those with growing energy needs - such as planning to install an EV charger or expand their home systems in the future.

With a 13kW setup and a high-capacity battery, you’re equipped to reduce grid dependency, boost long-term savings, and prepare for rising energy prices and grid instability.

Factors That Influence Battery Size in Australia

Selecting the right solar battery for home isn’t a one-size-fits-all decision. In Australia, various environmental, economic, and lifestyle factors can affect how much storage capacity your home really needs.

Understanding these influences is essential to ensure your solar battery not only meets your daily energy demands but also delivers long-term savings and reliability.

Below are the key elements every homeowner should consider before choosing their battery size.

1. Daily energy use: Larger families or energy-intensive homes need bigger batteries.
2. Solar production: Varies by system size, location, orientation, shading, and panel efficiency.
3. Backup needs: Do you need partial evening coverage or full-home backup?
4. Solar tariff structure: Time-of-use rates may encourage larger batteries for peak pricing arbitrage.
5. Available incentives: Programs like the cheaper home battery rebate can influence sizing choices.

Understanding Solar Panel Size vs Battery Size

While your solar panel system size dictates how much energy you generate each day, your battery size determines how much of that energy you can store for use during peak tariff periods or when the grid goes down.

A properly sized battery ensures you’re not sending excess energy back to the grid at lower feed-in rates.

It also provides greater energy independence, letting you power your home during blackouts or cloudy days.

Choosing the right solar battery means balancing your generation capacity with your household consumption and backup needs.

For example:

1. A 10kW solar system may generate ~40kWh/day, but a 10kWh battery only stores a quarter of that - limiting the duration of evening coverage.
2. If your solar panel size vs battery size ratio is too small, much of your generated energy may go unused (exported or lost), while oversized batteries may remain underutilised and cost-inefficient.

How to Choose the Right Battery Size – Step by Step

Choosing the ideal solar battery size for your home doesn’t have to be overwhelming. With the right approach, you can align your storage capacity with your household’s energy consumption and solar output.

This step-by-step guide is designed to walk you through the key considerations, from evaluating your electricity bills to calculating usable battery capacity. Whether you’re aiming for backup during outages or full-day coverage, following these steps will help you make an informed, cost-effective decision.

1. Review your electricity usage: Check your recent bills to find your average daily kWh usage.
2. Decide on storage goals: Do you want evening coverage only, or full-home backup?
3. Assess solar output: Estimate how much energy your panels generate daily.
4. Use the sizing table: Match your solar system and storage needs with recommended sizes (see section 2).
5. Check battery efficiency: Divide desired usable capacity by the battery’s depth-of-discharge rating (usually ~90% for lithium-ion).
6. Consult installers: Get quotes from well known experts like Solar Junction to factor in lifestyle, roof configuration, and pricing.

Conclusion

Choosing the right solar battery size ensures you make the most of your solar system and achieve meaningful energy savings.

Whether you have a 6.6kW, 10kW, or 13kW solar system, align your solar battery storage capacity with your usage patterns, blackout preparedness, and financial goals. A correctly sized battery delivers energy independence, tariff savings, and grid resilience.

Ready to go solar? Contact Solar Junction today to get expert support.