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Choosing the right size solar battery is one of the most important decisions for a Melbourne home. Too small and you run out of stored power before morning. Too big and you pay for capacity you never use. This guide explains how to size a solar battery based on how your household actually uses electricity.
Start with your daily electricity usage
The first step is knowing how much electricity your home uses each day. The most accurate source is your electricity bill, which usually shows your average daily usage in kilowatt-hours (kWh).
Most Melbourne households use somewhere between 15 and 25 kWh per day. Families with air conditioning, electric hot water, or an electric vehicle will sit at the higher end.
If you have a smart meter, your retailer can give you interval data that shows your usage hour by hour. This is the most useful information for sizing a battery, because it tells you not just how much you use, but when you use it.
Look at your evening usage
A solar battery is not meant to power your whole day. Its job is to store surplus solar from the daytime and release it at night, when the panels have stopped producing.
So the number that matters most is your evening and overnight usage, roughly from 5pm to 11pm and into the early morning. That is the load you want the battery to cover.
For a typical three to four person Melbourne household, evening and overnight usage often lands around 8 to 13 kWh. This is why a 10–13 kWh battery is the most popular size in 2026.
Match the battery to your solar system
A battery can only store the solar power your panels actually generate and that you do not use during the day. There is no point installing a large battery if your system cannot charge it.
A common 6.6kW solar system in Melbourne generates around 22 to 28 kWh on a good day, and noticeably less in winter. After daytime usage, that usually leaves 10 to 16 kWh of surplus to charge a battery. That surplus pairs well with a battery in the 8–13 kWh range.
Larger systems change the maths. A 13kW system can produce 50 kWh or more on a sunny day, which can comfortably support a 16–20 kWh battery for an energy-hungry household.
A simple sizing guide
As a starting point:
- Smaller homes / lower evening use: 6–10 kWh
- Typical Melbourne household (3–4 people): 10–13 kWh
- High evening use (ducted AC, EV, pool pump): 15–20 kWh
These are guidelines, not rules. The right size depends on your usage pattern, your solar system, and your budget.
Why a battery improves self-consumption
Solar Victoria notes that most households with solar panels only use around 25% of the energy they generate. The rest is exported to the grid for a low feed-in rate. Adding a correctly sized battery typically lifts self-consumption to around 50–60%.
In simple terms, the right size battery means you keep more of your own solar instead of selling it cheaply during the day and buying it back at a higher price at night.
Is the FOXESS CQ6 a good fit?
The FOXESS CQ6 is a modular battery, which makes sizing easier. It is built from 5.99 kWh modules that stack together, so a household can start around 12 kWh and add more capacity later if usage grows.
It uses LFP chemistry, which is known for being safe and long-lasting, and supports 100% depth of discharge, meaning you can use the full rated capacity. For homes that want to start at the right size today and expand as their needs change, a modular system like this is worth considering.
Don't forget rebates when sizing
The federal Cheaper Home Batteries Program offers a discount of around 30% on the upfront cost of an eligible battery. From 1 May 2026, the rebate is tiered: the first 14 kWh of capacity receives the full rate, with reduced rates above that.
This matters for sizing, because the most cost-effective batteries for most homes sit at or below that 14 kWh tier. To claim the rebate the battery must also be VPP-capable, though you are not required to actually join a virtual power plant.
Final thoughts
The right size solar battery is the one that matches your evening usage and the surplus your solar system produces, not simply the biggest one available. For most Melbourne households, that lands in the 10–13 kWh range, with larger homes needing more.
The best way to get an exact answer is to look at your interval data and your solar output together. If you would like help sizing a battery for your home, the team at Amos Green Energy can give you a tailored recommendation.