What Size Solar Battery Do I Need?
A Real Queensland Home Battery Case Study
Recently, a Queensland homeowner contacted us with a common question:
“I’m looking for a battery between 15kWh and 30kWh. I already have a 6.6kW solar system and my home is single phase.”
Rather than recommending the largest battery available, we started by analysing their electricity bill.
Here’s what we found.
The Home’s Energy Usage
The customer’s latest bill covered a 90-day period.
Key figures:
- Existing solar system: 6.6kW
- Daily electricity usage: 16.4kWh
- Daily solar exports: 16.0kWh
- Electricity purchase rate: 34.9 cents/kWh
- Solar feed-in tariff: 3 cents/kWh
At first glance, one number stood out.
The homeowner was exporting almost the same amount of energy that they were consuming every day.
What Does This Mean?
Their solar system is generating plenty of energy.
The problem is that much of that energy is being exported to the grid during the day for only 3 cents per kWh.
Later, when the sun goes down, electricity needs to be purchased back from the grid at almost 35 cents per kWh.
In other words:
They’re selling low and buying high.
Over 90 days, this homeowner exported 1,437kWh of solar energy and received only $43 back from their electricity retailer.
Our Recommendation
Based on the customer’s energy usage and solar exports, a 16kWh home battery would be an excellent fit.
Why?
Because the home consumes around 16kWh per day, which means a battery of similar size can store much of the excess solar energy generated during daylight hours and make it available during the evening.
What About a 24 kWh Battery?
A 24kWh battery could also work well for homeowners who:
- Are planning to buy an EV
- Expect their energy usage to increase
- Want additional backup capacity
And a 30 kWh Battery?
A 30kWh battery is certainly possible.
However, based on the current usage patterns, it would likely be larger than necessary and may take longer to deliver a return on investment.
The Takeaway
When it comes to batteries, bigger isn’t always better.
The best battery size depends on your actual energy usage, solar production and export patterns. Not just the size of your solar system.
In this case, the customer’s electricity bill told us everything we needed to know.
Choosing the right battery storage system is about matching your energy usage, solar production and future needs.
Could This Apply to Your Home?
If you’re not sure what size solar battery is right for your home, we’re happy to help.
Simply send us a recent electricity bill to info@weglow.com.au and our team can provide a personalised battery recommendation based on your actual energy usage, solar production and future energy goals.
Whether you’re considering a home battery, upgrading your existing solar system, or looking to maximise your solar savings, we’ll help you find the right solution.