So, you’ve got solar panels or you’re planning to install them. Great move! But the next big question on your mind might be: What battery size do we actually need at home? That’s something many Aussie homeowners are asking—especially now that battery rebates are making it more affordable than ever to store solar energy for nighttime use or backup power.

Let’s break this down together in a practical, no-nonsense way.

Why Battery Size Matters

Choosing the right battery size isn’t just about throwing in the biggest unit you can afford. It’s about matching your home’s energy habits with a storage system that fits like a glove. Too small, and you won’t store enough to cover your evening and overnight needs. Too big, and you might waste money on capacity you never use.

So how do we figure out the sweet spot?

We need to look at a few key things:

• How much energy you actually use
• When you use that energy
• How much solar you’re generating
• What you want the battery to do—save money, provide backup, or go fully off-grid

Typical Energy Usage in Aussie Homes

Let’s start with the basics. The average Australian household uses anywhere between 15 to 25 kilowatt-hours (kWh) of electricity per day. But that’s just an average. Small homes or units might only use 8–12 kWh per day, while large families with pools, air conditioners, and EVs could be clocking 30–40 kWh or more.

To get an accurate picture, have a look at your electricity bills from the past year. They’ll usually show your average daily consumption.

Also consider when you’re using that electricity. If you’re home during the day, you might use your solar power directly. But if you’re out most of the day and the bulk of your usage happens in the evening, that’s when battery storage becomes valuable.

What Most Households Are Installing

From what we’re seeing in the market—and from installers across Australia—most families are opting for batteries between 8 kWh and 13 kWh. It’s that middle ground that tends to give you solid solar savings without going overboard on upfront cost.

Let’s break it down by household size:

• 1–2 person homes using 8–15 kWh/day: A 5–7 kWh battery is usually enough to shift your solar power into the evening hours.
• 3–4 person homes using 16–25 kWh/day: A 10–13 kWh battery will likely cover most of your night-time usage and can even power the home during short blackouts.
• Larger households or those with electric vehicles, pools, or big heating/cooling loads may need 15 kWh or more to get real benefit.

This isn’t just guesswork—these numbers line up with how real families are using and storing their solar energy.

How to Choose the Right Size for Your Goals

Let’s say you’re not sure what you want the battery for—are you chasing savings, looking for blackout protection, or dreaming of being fully off-grid?

Here’s how battery sizing ties into each goal:

1. For Savings Only:

If your aim is to reduce power bills, you want a battery that soaks up your excess solar during the day and gives it back in the evening. The trick is to match your battery to your excess solar generation. There’s no point in buying a 13 kWh battery if your system only overproduces by 5 kWh daily.

2. For Backup Power:

A slightly bigger battery is a good idea here. Aim for enough capacity to run your essential appliances (fridge, lights, Wi-Fi, a few power points) for several hours. This usually means a minimum of 10 kWh, especially if you want to get through overnight blackouts.

3. For Going Off-Grid or Near It:

This is where things get serious. You’ll need 15 to 25+ kWh of storage, possibly more, and often a backup generator. This kind of setup suits regional and remote homes, or people really committed to energy independence. But it does come with higher upfront costs.

The Cost Side of Things

Battery prices in Australia are still on the higher end, but they’re dropping—especially with rebates coming in.

As of mid-2025:

• Expect to pay around $1,000 to $1,200 per kilowatt-hour installed.
• A decent 10 kWh battery system will cost you about $10,000–$12,000 before rebates.
• The new Federal Battery Rebate, starting July 1st, 2025, will knock off roughly 30% of that cost—about $370/kWh, up to 50 kWh.
• Some states, like NSW and Victoria, also offer extra rebates or VPP incentives, so it’s worth checking what’s available in your area.

This means a 10 kWh battery could end up costing you closer to $7,000 after rebates—much more manageable than just a few years ago.

What Else Affects Battery Size?

There’s more to consider than just capacity. Here are a few tips:

Match with your solar system size.

Got a 6.6 kW solar system? Then you’re probably generating 25–30 kWh/day in summer. A 10–13 kWh battery makes sense here, assuming you don’t use most of your power during the day.

Look at your inverter.

Some hybrid inverters have limits on how much battery they can handle. Others can be upgraded. You’ll want to make sure your battery choice plays nicely with the rest of your system.

Think about the power output.

Battery storage (kWh) tells you how much energy is stored, but the inverter’s power rating (kW) tells you how fast you can use it. For example, if your battery outputs 5 kW max, that’s enough to run a kettle, lights, and fridge—but maybe not your air con at the same time.

Leave room to expand.

Some battery systems are modular. That means you can start with 5–7 kWh today and add more capacity later. It’s a smart way to scale up as your needs grow.

So, What’s the Sweet Spot?

For most Aussie families, a 10 to 13 kWh battery hits the mark. It’s big enough to make the most of your solar generation, gives you good backup capacity during outages, and doesn’t break the bank—especially with rebates starting soon.

That said, every home is different. Here’s a quick rule of thumb:

Battery Size = (Daily Energy Use) x 25% + 2 kWh buffer

So if you use 20 kWh a day, that gives you a starting point of 7 kWh—but if you want blackout protection, going up to 10–12 kWh would be smarter.