Getting the right battery size can make a huge difference in how much money you save, how much solar power you actually use, and how often you’ll rely on the grid—especially during those peak evening hours.
Too small, and you’ll run out of power when you need it most. Too big, and you might spend more than you need to. The sweet spot? That’s what we’re here to nail down.
In Australia, most homes use between 10 and 30 kilowatt-hours (kWh) of electricity a day—so the right battery size depends on your usage, your solar panel setup, and how much energy you want to store.
We’re going to break it all down in simple terms, using real Aussie examples.
Let’s make this whole solar battery thing way less confusing—so you can make a smart choice and actually get value out of your solar setup.
How Battery Size Impacts Solar Savings
Battery size comes down to one thing—how much energy your home uses and how much you want to store for later.
The bigger the battery (measured in kilowatt-hours or kWh), the more solar energy you can hold onto and use at night or when it’s cloudy.
A 5kWh battery can usually handle the evening needs of a smaller household, but for a larger family with more appliances running, something closer to 10–13.5kWh makes more sense.
Here’s what that actually means for your wallet and lifestyle:
- More storage means less energy pulled from the grid, which helps cut down your power bills—especially if you’re on time-of-use tariffs.
- A decent-sized battery can also keep the lights on during blackouts, which is a big deal in parts of Australia where the power grid isn’t always reliable.
- You’ll end up using more of your solar energy, instead of selling it back to the grid for a few cents.
A few years ago, selling extra solar power to the grid made financial sense.
Now? Feed-in tariffs have dropped, so keeping that energy and using it yourself gives you more value.
That’s why battery size matters—it decides how much of your solar power stays with you and how much goes to the energy company for almost nothing.
If you’re looking for long-term savings, the right battery size makes a big difference in how quickly you’ll see a return on your investment.
Every kWh counts when it comes to saving money, keeping your home powered, and getting the most out of your solar system.
Average Solar Battery Size for Australian Homes
Most Aussie homes use somewhere between 10 and 30 kilowatt-hours (kWh) of electricity each day.
The right battery size depends on how much of that power you want to store and when you use it.
You’ll see a lot of talk about 5kWh, 10kWh, and 13.5kWh batteries—they’re the most common sizes people go for.
Here’s a quick idea of what they actually cover:
- 5kWh works well for smaller households that don’t use much power at night.
- 10kWh suits the average family that wants to run a few big appliances and keep the essentials going after sunset.
- 13.5kWh is a solid pick if you’ve got a bigger household, work from home, or use a lot of power into the evening.
One of the most popular options in Australia is the Tesla Powerwall, which has a capacity of 13.5kWh.
It’s known for its sleek design, strong performance, and easy-to-use app.
Other good picks on the market include Sonnen, LG Chem, and Alpha ESS—each with different sizes and features depending on your needs and budget.
Choosing between them usually comes down to a mix of daily energy use, how much solar you’ve got, and whether you want blackout protection.
Getting the battery size right helps you store more solar energy and use it when you need it most—without relying too much on the grid.
Matching Battery Size to Your Energy Usage
One of the easiest ways to figure out the right battery size for your home is to start with your electricity bill. Most Aussie energy bills show your average daily usage in kilowatt-hours (kWh).
You’ll usually find this on the second or third page under something like “daily usage” or “average consumption.”
Let’s say your bill shows 18kWh per day—that’s how much energy your home uses on average. From there, you can match your needs to a battery size.
Your usage might be spread across the day, but solar panels only generate power when the sun’s out. So the real question is: how much energy do you use at night or when your panels aren’t producing?
That’s where peak and off-peak pricing comes in. Power costs more during peak times—usually early evening when everyone’s home.
A battery lets you store solar power during the day and use it later when electricity prices go up. That’s how you start saving.
Here’s a simple guide to match your usage:
| Daily Usage (kWh) | Recommended Battery Size |
| 5–10kWh | 5kWh battery |
| 10–20kWh | 10kWh battery |
| 20–30kWh | 13.5–15kWh battery |
This isn’t exact science, but it’s a solid starting point.
Keep in mind—you don’t always need to cover 100% of your energy use with a battery. Even partial coverage can make a real dent in your power bills and give you some energy independence.
The key is to balance what you use, when you use it, and how much solar power you’re generating.
Matching Battery to Solar Panel Size
If you already have solar panels or you’re thinking about getting them, it’s worth making sure your battery size actually matches the solar system you’ve got.
This part is easy to overlook, but it really matters.
Oversizing a battery sounds harmless, but it can lead to wasted money and power.
If your panels don’t generate enough excess energy during the day, a big battery won’t fill up.
That means you’re paying for storage you’re not using.
Most Australian homes are running around 6.6kW solar systems—they’re popular because they hit the sweet spot for rebates and output.
For that size, a battery in the 5kWh to 10kWh range usually works best.
There’s a handy rule that helps: aim for a solar-to-battery ratio of 1.5 to 2 times.
So if your battery is 10kWh, your panels should ideally generate 15–20kWh a day to keep it charged and useful.
Here’s what happens when the setup’s well balanced:
- You charge your battery fully most days.
- You use that stored energy at night when rates are higher.
- You reduce how much you need to buy from the grid.
If your battery is too large for your solar system, you’ll always have a chunk of it sitting empty.
That doesn’t help with savings and just slows down your return on investment.
So getting the balance right between solar production and battery storage is key to making your setup work as it should—efficient, simple, and worth the cost.
On-Grid vs Off-Grid Battery Size
On-grid and off-grid homes need very different battery setups.
If you’re on the grid, your home still has access to electricity from your power company. The battery is mostly there to help with things like peak-hour savings, blackout backup, and storing your solar energy for later.
That means you can get away with a smaller battery, usually around 5kWh to 13.5kWh, depending on how much energy you want to shift into the evening.
A lot of Aussie families with a 6.6kW solar system go for something like a Tesla Powerwall (13.5kWh) or a 10kWh Alpha ESS—enough to keep the fridge, lights, and internet going during an outage and save on evening rates.
On the other hand, off-grid homes need to go bigger.
You’ll need a battery large enough to power everything, including overnight use, cloudy days, and maybe even several days of poor solar production.
That usually means 20kWh to 40kWh or more, plus a backup generator just in case.
Some regional properties in WA or remote parts of QLD use setups like:
- 10kW solar system
- 30kWh battery bank
- Diesel backup generator
The goal for off-grid isn’t just about saving money—it’s about reliability. If your battery runs out, there’s no grid to lean on.
So sizing needs to cover your daily use and then some. For grid-connected homes, you’re just filling the gaps.
For off-grid, your battery is the entire supply.
Real Examples of Solar Battery Sizing in Australian Homes
Here’s a look at how Aussie homes are actually sizing their solar batteries—real setups, real results.
Small family in Sydney – 5kWh battery
- 2 adults, 1 child in a three-bedroom home.
- Daily energy use: around 10kWh.
- Solar system: 5kW panels.
- Battery: 5kWh BYD unit.
- Goal: cover evening use and reduce peak-hour costs.
- Result: Battery charges fully most days and lasts until late at night. Power bills dropped by over 40%.
Large household in Melbourne – 13.5kWh battery
- 2 adults, 3 teenagers. Multiple TVs, gaming consoles, and laundry runs.
- Daily use: 25kWh+.
- Solar system: 6.6kW panels.
- Battery: Tesla Powerwall (13.5kWh).
- Goal: heavy reliance on solar, reduce grid usage, blackout support.
- Result: Significant energy savings. Battery handles most of the evening load and keeps internet/fridge running during outages.
Regional off-grid home in WA – 20kWh+ battery
- Located outside Albany. No grid connection.
- Couple running a small home business.
- Daily use: 15–20kWh depending on season.
- Solar system: 10kW panels.
- Battery: 24kWh lead-acid bank with backup diesel generator.
- Goal: complete independence from the grid.
- Result: Reliable power through most of the year. Generator kicks in for backup during storms or long cloudy stretches.
These examples show how battery size really depends on lifestyle, location, and whether you’re on or off the grid.
Cost vs Size: What’s the Sweet Spot?
When you’re looking at battery size, cost per kilowatt-hour (kWh) is a good way to compare value.
Smaller batteries often cost more per kWh, while bigger ones offer better bang for your buck—but only if you can use the full capacity.
Here’s a rough idea of average battery prices in Australia:
| Battery Size | Approx. Cost (AUD) | Cost per kWh (AUD) |
| 5kWh | $5,000–$6,000 | $1,000–$1,200 |
| 10kWh | $9,000–$11,000 | $900–$1,100 |
| 13.5kWh (Powerwall) | $14,000–$16,000 | $1,050–$1,185 |
A 10kWh battery often hits the sweet spot.
It’s big enough to cover evening usage in most homes but not so big that you’re paying for storage you rarely fill.
ROI depends on how much solar you can store and use during expensive times.
Using stored energy at night or during peak tariffs makes a big difference over time.
Some Aussies are also joining Virtual Power Plant (VPP) programs.
You let your battery share energy with the grid when needed and get paid for it.
This, plus energy arbitrage—buying energy when it’s cheap, using or selling it when it’s expensive—can help speed up your payback period.
If your battery’s right-sized and smartly used, it can pay itself off in 7–10 years, sometimes faster with rebates or VPP incentives.
Australian Government Rebates for Solar Batteries
Based on the latest info from SolarQuotes, several Australian states and territories offer rebates, grants, or loans to help with the cost of installing a home solar battery.
The deals vary depending on where you live, but they can make a pretty big difference to your out-of-pocket costs.
Here’s a quick breakdown of what’s available:
- Victoria (Solar Homes Program): Households can apply for a solar battery rebate of up to AUD $2,950. To be eligible, you need to already have solar panels installed and meet other income and property requirements.
- South Australia (Home Battery Scheme): While this rebate officially closed in 2022, many people still benefit through Virtual Power Plant (VPP) programs that offer subsidised batteries.
- Australian Capital Territory (Next Gen Energy Storage Program): Rebates are still available through this program—up to AUD $3,500, or AUD $825 per kilowatt-hour of battery capacity, whichever is less. You need to use an approved installer and live in the ACT.
- New South Wales (Empowering Homes): This scheme has ended, but interest-free loans for solar and batteries were previously offered. Check with local councils—some still run their own programs or pilot trials.
- Northern Territory (Home and Business Battery Scheme): This has also closed, but again, check local councils or regional updates for new funding rounds.
Some federal incentives may still apply indirectly, like through the Small-scale Renewable Energy Scheme (SRES), which reduces the cost of installing solar panels—but it doesn’t cover batteries directly.
If you’re thinking about getting a solar battery, it’s worth checking what’s still active in your area, as rebate programs can change quickly or reopen depending on budget cycles.
Battery Lifespan and Performance by Size
Battery lifespan is measured in cycles—one full charge and discharge counts as one cycle.
Most modern solar batteries are rated for around 6,000 to 10,000 cycles, depending on the brand and how deeply they’re discharged each time.
That’s where Depth of Discharge (DoD) comes in. If you regularly drain your battery all the way, it wears out faster.
A battery with 90% DoD is more durable than one that only allows 50%. Bigger batteries tend to last longer in real-world use because they cycle less often.
For example, if you only use 5kWh per night but you’ve got a 13.5kWh battery, it doesn’t have to work as hard or go through deep discharges.
That means slower wear and better long-term performance.
Most lithium-ion batteries used in Aussie homes come with 10-year warranties, but actual performance can vary based on usage.
Higher-quality batteries like the Tesla Powerwall or Sonnen often hold up better over time compared to cheaper models.
Choosing the right size helps spread the load and keep your battery in good shape for years.
Key Takeaway
Getting the right solar battery size doesn’t have to be confusing.
Just look at how much power you use each day, how much your solar panels produce, and when you actually need that energy.
Most Aussie homes fall somewhere between 5kWh and 13.5kWh, but off-grid setups usually need more to stay fully powered without the safety net of the grid.
Bigger isn’t always better—it’s about finding a size that fits your lifestyle and keeps your battery working efficiently for years.
Think about what matters most: saving money, backup during blackouts, or just using more of your own solar energy.
If you’re still unsure or want help designing a system that actually works for your home, that’s what we do at Off Grid WA.
We’ve helped heaps of households across Australia get the right battery size and setup for their needs.
Check us out at 👉 offgridwa.com.au and let’s build something that powers your home properly.
Frequently Asked Questions
What happens if my battery is too small?
Explain limitations and reduced savings.
Can I add more batteries later?
Yes, but not always simple. Compatibility matters.
What size battery is best for blackout protection?
At least 10kWh for short outages. More if running heavy appliances.
Do I need a solar battery if I’m home during the day?
Depends. Might save less, but still helpful during outages or high tariffs.
How long do solar batteries last in Australia?
Typically 10–15 years, depending on use and climate.
