Solar batteries are quickly becoming one of the most popular upgrades for Australian homes with rooftop solar. With electricity prices rising and new battery incentives available, many households are asking the same question:
What size solar battery do I actually need?
Choosing the right battery size matters. Too small and it may run out before the night is over. Too large and you might pay for storage capacity you rarely use.
The ideal battery size depends on several factors including your household energy usage, the size of your solar system, and whether you plan to power things like electric vehicles or backup circuits during blackouts.
This guide breaks down the key things that influence battery sizing so homeowners can make a more informed decision.
A solar battery stores excess electricity produced by your solar panels during the day so it can be used later when the sun goes down.
Without a battery, most solar homes export unused energy back to the grid during the day and then buy electricity back from the grid at night. A battery changes that dynamic by storing surplus solar energy for evening use.
In practical terms, a battery allows homeowners to:
• use more of their own solar power
• reduce electricity purchased from the grid
• potentially provide backup power during outages
• participate in Virtual Power Plant (VPP) programs in some states
Because batteries store energy rather than generate it, their usefulness depends heavily on how much electricity your home uses after sunset.
Solar batteries are sized using kilowatt-hours (kWh), which measures how much energy the battery can store.
For example, a 10 kWh battery can theoretically supply:
• 1 kW of power for 10 hours
• 2 kW for 5 hours
• 5 kW for 2 hours
In a typical Australian household, evening energy usage might include:
• lighting
• refrigeration
• cooking appliances
• entertainment systems
• heating or cooling
A battery simply stores enough energy to cover some or all of that nighttime demand.
While every household is different, there are some common battery sizes that work well for different types of homes.
|
Home Type
|
Daily Electricity Use
|
Suggested Battery Size
|
|
Small household (2–3 people)
|
~12–15 kWh
|
5–10 kWh battery
|
|
Average family (4–5 people)
|
~18–25 kWh
|
10–15 kWh battery
|
|
Large home or EV charging
|
30 kWh+
|
15–25 kWh battery
|
Many of today’s popular home batteries sit around the 10–15 kWh range, which provides enough storage to cover a large portion of evening usage for many households.
However, the best size always depends on your actual electricity consumption patterns.
Several variables influence how large your battery should be.
Your Evening Energy Usage
The most important factor is how much electricity your household uses after sunset.
If most of your energy consumption happens during the day while solar panels are generating power, a smaller battery may be sufficient.
If your household uses a lot of electricity at night, such as running air conditioning, cooking appliances, or multiple devices, a larger battery may be more suitable.
Your solar system must generate enough energy to charge the battery in the first place.
For example, a large battery connected to a small solar system may never fully charge, limiting its usefulness.
A well-designed solar system typically balances:
• solar panel production
• daytime household consumption
• battery charging requirements
This ensures there is enough excess solar energy available to fill the battery during the day.
Electric vehicles are becoming increasingly common in Australian households.
Charging an EV can add significant electricity demand, particularly in the evening when many people plug in their vehicles.
If your home currently has an EV, or you plan to purchase one in the future, battery sizing may need to account for this additional energy usage.
Some homeowners choose larger battery systems specifically to support EV charging using stored solar energy.
Some batteries can provide backup power during blackouts, depending on how the system is configured.
If backup power is important, battery sizing may be influenced by which appliances you want to keep running during an outage.
For example, a backup circuit might include:
• refrigerator
• lights
• internet router
• basic power outlets
Larger batteries can run more appliances for longer periods during a power outage.
Battery technology is evolving rapidly, and some systems now allow homeowners to expand their storage capacity over time.
This means a household might install one battery initially and add additional capacity later as their energy needs change.
For example, recent updates in the home energy storage market suggest that some systems may support future expansion options, allowing households to increase storage capacity as technologies develop or as electricity usage grows.
Planning for future flexibility can be particularly useful for households considering:
• electric vehicles
• larger solar systems
• increased home electrification
Starting with a modest battery and expanding later can sometimes provide a balanced approach.
When choosing a battery size, there are a few common pitfalls to avoid.
Oversizing the Battery
A battery that is significantly larger than your solar production may rarely fill completely. This can reduce the overall financial return on the system.
Undersizing the Battery
A battery that is too small may run out early in the evening, forcing the home to rely on grid electricity overnight.
Ignoring Future Energy Needs
Energy usage often increases over time as homes add new appliances, electric heating, or EV chargers.
Considering future needs can help ensure the battery remains useful for years to come.
Choosing the right solar battery size is about balancing energy storage with your household’s electricity usage.
Factors such as solar system size, evening energy demand, EV charging, and backup requirements all influence the ideal battery capacity.
For many Australian homes, a battery in the 10–15 kWh range provides a practical balance between cost and energy independence. However, the best solution always depends on the specific needs of the household.
As solar and battery technology continues to evolve, flexible systems and expanding storage options are making it easier for homeowners to tailor energy solutions that grow with their needs.
Ready to maximise your savings and take control of your power?
Let’s power your home for a better tomorrow.
1. Australian Government – Solar PV and Batteries (Energy.gov.au):
https://www.energy.gov.au/households/solar-pv-and-batteries
2. YourHome.gov.au – Photovoltaic Systems:
https://www.yourhome.gov.au/energy/photovoltaic-systems
3. SolarQuotes – Understanding Solar Batteries
https://www.solarquotes.com.au/101-guides/understanding-batteries/
4. SolarChoice – Solar Battery Guide
https://www.solarchoice.net.au/solar-batteries/
5. Tesla – Powerwall Information
https://www.tesla.com/en_au/powerwall