If you’re shopping for a solar battery, you’re probably wondering how big a battery you need. A solar consultant might be telling you one thing, while another is telling you something else. It’s enough to throw your hands up in frustration.
At PSC Energy, we understand what you’re going through. Figuring out the best battery size is what we do for our customers. It can be a bit of a learning curve but don’t worry, we’re here to lay it out for you.
In this article, you’ll learn about the following:
- How Do You Get the Most Solar Power?
- Energy Priorities in Your Solar Panel System
- Do You Want to Join a Virtual Power Plant (VPP)?
- How to Choose the Right Solar Battery Size
- Backup Power: How Much Is Enough?
By the end of this article, you’ll understand what you need to consider when sizing a solar battery.
How Do You Get the Most Solar Power?
Did you know that rooftop solar panel adoption in Australia has now topped 30%? It’s a huge achievement and a testament to how much Australians love clean, renewable energy.
Solar power is not only great for the planet but also for your wallet. With so many people embracing solar, we’re seeing some impressive results like homes generating more energy than they need during the day.
But with all this success comes a new challenge. When demand for energy drops during peak solar hours, it leads to a situation that’s raised concerns. We’re talking about the so-called “sun tax.” If you’ve heard the term, you know it’s got solar homeowners (and the entire solar industry) buzzing.
The sun tax is just two-way pricing from energy distributors to limit solar energy exported from homes to the grid during the day.
The sun tax is a symptom of a problem that can be fixed easily with solar batteries.
Here’s the good news: PSC Energy is installing battery storage systems. Thanks to support from the New South Wales Peak Demand Reduction Scheme and the Federal Cheaper Home Batteries Program, these systems are more affordable and accessible than ever.
But the big question remains: What size battery is right for your solar setup? Let’s break it down by understanding how battery storage works and why maximizing self-consumption is key.
If you’re interested in learning a bit more about the solar battery rebate, you might want to check out the following article titled, Everything You Need to Know About the Home Battery Rebate for NSW.
Energy Priorities in Your Solar Panel System
Before we get into answering the titular question, we need to talk about how to use your home-grown electrons.
The way battery storage works is simple: it’s focused on making the most of your solar energy. Batteries are designed to prioritise using your homegrown electricity first, so you rely less on power from the grid. Here’s how it works:
- Solar Power Comes First: Whenever the sun is shining, your solar panels power your home directly. Appliances, lights, and anything else running in your house will pull from the solar panels first. Once the home loads are supplied, then excess energy can be tucked into a battery for use later.
- Excess Energy Goes to Your Battery: Once your home’s needs are met, any leftover solar energy is stored in your battery for later use. They will discharge during the day if needed. This is to avoid pulling from the grid.
- Grid Power as a Last Resort: If your panels aren’t producing (think nighttime or cloudy weather) and your battery is drained, then – and only then – will your home pull energy from the grid.
It’s important to note that it’s possible for your home to be pulling energy from the grid, your battery, and solar panels all at the same time to meet the demand of your home. We want to set you up to take as much as possible from the solar and the battery before resorting to the grid.
If you have a system with a battery, you’re set up to get the most out of your solar investment while keeping your energy costs low.
What About Feed-in Tariffs?
When the solar is pumping, that extra energy is sold to the grid because the first two energy priorities are met. Your home is supplied, and the battery is charged to 100%.
So, what happens when your panels are generating more electricity than your home can use, or your battery can store?
That’s where feed-in tariffs (FiTs) come in.
Once your battery is 100% charged, any extra energy gets sent to the grid, and you’re paid a small rate for contributing. It’s not a huge payout, but every little bit helps shorten your payback period.
Because FiT rates decreased over the years in Sydney, many homeowners are finding that battery storage is a great option for saving money. Instead of sending all that extra energy to the grid, you’re able to store it and use it for later.
If you’re interested in learning how you can turn your solar battery into a source of passive income, you might want to check out the following article titled, Variable Feed-in Rates and VPPs in NSW.
Ready to go solar? Click here.
Do You Want to Join a Virtual Power Plant (VPP)?
Of course, with Virtual Power Plants and other cool technology coming to Australia, it means we’re using batteries in different ways and not necessarily for maximum self-consumption.
A VPP works by pooling the energy stored in batteries from multiple homes into one big virtual resource. This collective energy can be used to support the grid during high-demand periods or even sold back to energy providers.
For homeowners, participating in a VPP can mean extra income.
Platforms like Amber Energy let you sell your stored power at premium prices during times of high demand. You’re making money and you’re also helping stabilize the grid. It’s a great way to get more out of your battery system.
Beyond energy trading, batteries also provide peace of mind as backup power sources. If you live in a rural area or a place prone to blackouts, a battery system can keep your lights on, your fridge running, and your internet connected when the grid goes down.
You’ve got to ask yourself: what would you be willing to pay for energy when the grid is down?
You can use your battery for different tasks at the same time. It can be programmed for maximum self-consumption while also being connected to a VPP.
Managing your battery and how you want it to behave is controlled by you. Use the Enphase Enlighten App or the Tesla App to program your battery.
If you’re interested in learning a bit more about VPPs, you might want to check out the following article titled, What is a Virtual Power Plant (VPP)?
How to Choose the Right Solar Battery Size
But we still haven’t answered the question: what size battery should I buy for my home?
The answer is: it depends.
It depends on:
- How much backup power you want.
- How many solar panels you have on your roof.
- How well your solar system is working.
- And what your needs are once the sun goes down.
For example, let’s look at a 10kW solar system in Sydney:
- On average, this system generates about 39kWh of energy per day.
- In summer, production can climb to 60kWh on sunny days.
- In winter, production may drop to around 18-20kWh daily.
As you can see, in the summertime, when there’s more sun, you’ll find that you have a lot more excess than in wintertime.
The Importance of Customising Your System:
On the days when 60kWh are produced, the home may only be consuming 20 to 30kWh, which means you’ll have an excess of 20 to 30kWh of energy to be able to store. This is great.
However, in winter, what you might find is that the same 20 to 30 excess kilowatt-hours that you had in summer may only be 10 to 15kWh in wintertime.
If someone sold you 30kWh of battery storage to bolt onto a 10kW system, you can bet your bottom dollar that, in winter, particularly on those cloudy days, you would not charge those batteries to 100%.
It’s important to match your system to your battery backup. Oversizing your battery system to accommodate summer production only is a recipe for disappointment. In the wintertime, that is.
We customise every system we install because every household is different.
If you’re home during the day and using energy for things like air conditioning or appliances, you might not need much battery storage. You’re already using your solar energy.
But if your house is empty during the day and your energy use spikes at night, a larger battery might be the way to go.
It will be different from one family to another. It all depends on your energy habits.
Please Note: If you’re a family that already has solar on your home and you’re lucky enough to have energy use monitoring (like Enphase systems have), you’ll be able to easily and quickly work out the size of the battery that you need for your home.
You can do this by seeing how much excess energy you sell to the grid. The goal is to take that excess energy, store it, and keep it for nighttime use.
Adapting to the Seasons
Your energy needs aren’t the same all year round, and neither is your solar production. That’s why batteries are so valuable. They let you adjust settings based on the season.
During summer, you can focus on storing and using excess solar energy. In winter, you might prioritise conserving power for essential loads during the long, dark nights.
Battery Storage Guidelines:
Your battery’s kWh should be about double your system’s kW size. At PSC Energy, we recommend pairing 5kW of solar panels with 10kWh of battery storage as a general rule of thumb. It’s pretty simple math, as you can see.
For instance, a Tesla Powerwall 3, which has a storage capacity of 13.5kWh, requires approximately 6.6kW of solar panels to charge effectively.
Scaling up, a 27kWh battery (two Powerwalls) would need about 13-14kW of solar capacity to operate efficiently throughout the year.
Of course, the average system we install is around 10 – 11kW. A 6.6kW system will struggle to keep up with your evolving energy needs. This is only an example, not a recommendation.
If you’d like to learn more about Tesla products, we recommend you check out the following article titled, Tesla Powerwall 3 Review: An In-Depth Look at Tesla’s New Solar Battery.
Power up your savings. Click here.
Backup Power: How Much Is Enough?
One of the biggest perks of battery storage is having backup power during outages. But how much backup do you really need?
If you have a 10kWh battery and want to reserve half of it for emergencies, that leaves you with 5kWh for daily use. Is that enough to meet your needs? It quickly becomes a 5kWh battery if you’re saving half of it for backup.
It’s possible that a 15kWh battery be a better fit. If you have a 15kWh battery, you can program 10kWh for daily use with 5kWh for backup. Striking the right balance between backup power and daily usage is critical to optimising the system’s value.
Some advanced batteries, like the Tesla Powerwall 3 and Enphase systems, come with smart features like Storm Watch. This technology detects severe weather and charges your battery ahead of time, so you’re prepared for blackouts. It’s an added layer of security so your home stays powered when you need it most.
Because of features like this, it’s possible to prioritise self-consumption or trade energy on a VPP until a likely blackout approaches. When it’s likely, the battery’s in-built intelligence will charge up and prepare for the storm.
What to Expect During Blackouts
It’s important to set realistic expectations for your battery system during blackouts.
For single-phase homes, a battery can often back up the entire house. Because all loads are on a single-phase, everything can be backed up.
But for three-phase homes, the system might only support specific loads, like your fridge, WiFi, and some lighting. You’ll only be able to back up a third of your home’s electrical needs.
Think about what’s most important for you and your family during an outage. Is it keeping the fridge running? Staying connected online? Or just having lights on? By identifying your priorities, you can work with your installer to ensure your battery system meets your needs. It’s a matter of choosing which phase to backup.
If you’re interested in learning a bit more about the benefits of solar batteries, you might want to start with the following article titled, 7 Benefits of Adding a Battery to Your Solar System.
Let’s talk solar savings. Click here.
With Battery Storage, It’s Easy Sunny
Consulting with a professional energy specialist is essential to ensure your solar and battery setup is optimized for year-round performance. With the right guidance, homeowners can unlock the full potential of their solar investment, reaping both financial and environmental benefits for years to come.
Choosing the right solar battery for your home is about more than just capacity. It’s about understanding your energy habits and planning to meet those needs. By customising a system to your unique needs, you can enjoy lower energy bills, greater independence from the grid, and the peace of mind that comes with having reliable backup power.
At PSC Energy, we consult with you to understand your energy needs and goals. We design every custom system for your energy success. With the right guidance, you’ll unlock the full potential of your solar investment and enjoy the benefits for years to come.
If you’re interested in learning a bit more about the battery market, you might want to check out the following article titled, Best Home Solar Batteries for 2025.
