Understanding solar battery sizes

Investing in solar battery storage is a smart step towards maximising the benefits of solar energy and cutting down on your electricity bills. However, selecting the right size solar battery for your property can be a bit tricky. The size of the battery you choose plays a crucial role in optimising both performance and cost-efficiency.

To make this decision easier, we’ve outlined a simple process to help you determine the ideal battery size for your home. Key factors to consider include your average energy consumption, the capacity and output of your existing solar system, and your budget. It’s also important to factor in the number of people and appliances in your household and think about whether these will increase over time.

What to think about when choosing your solar battery size

There’s no universal answer for the perfect solar battery size. Your energy needs, the size of your solar system, your reasons for getting a battery, your budget, and even your location all play a part in the decision.

Let’s break it down.

Your budget

Budget is the first thing to consider when thinking about solar batteries. While they can save you money over time, the upfront cost is still something to think about. Luckily, many places in Australia offer rebates to help lower the cost of installing solar batteries. Be sure to check your state’s policies to see if you’re eligible.

Your location

Where you live plays a big role in the size of the solar battery you need. Environmental factors can affect how well your solar system – and your battery – work. For example, if you live in a place with constant shade, your panels might not generate enough power to make a solar battery worthwhile.

While having solar panels and a solar battery sounds like a great idea, it’s not always necessary. The efficiency of your solar panels depends on factors like your location, the direction they face, and the local climate. These all impact how well your system works and whether a battery is a good investment.

Your energy usage

How much energy you use daily will have a big impact on the size of battery you need. If you have high energy demands during weekends, for example, storing up energy through the week can help reduce your reliance on the grid.

In Australia, households typically use between 8kWh (for a single person) to 20kWh (for a larger household). How much power you need depends on the size of your home and how much you rely on energy-hungry devices like air conditioning or heating systems.

Homes with solar power use about one-third of their electricity during the day, while the rest comes from the grid, typically in the evening when demand is higher. This is what you’ll want to base your battery size on.

To estimate your energy needs, look at your energy bill or, if you have a smart meter, check your consumption more accurately.

Your reasons for adding a battery

Why do you want a solar battery? This will help guide your choice. Not everyone with a solar system needs a battery. Some people just want to use as much of the energy they generate as possible. If you’re aiming to save money and don’t mind using some grid power, a smaller battery could work.

If you’re keen to reduce reliance on the grid, or even go off-grid entirely, you’ll need a larger battery. A solar battery can also be a backup power source during blackouts, but unless power outages are frequent in your area, you might not need a big one.

The size of your solar system

The size of your solar system is a major factor in choosing the right battery size. Your battery can only store the energy your solar array generates, so the bigger your system, the more energy you can store.

When people ask if a solar battery is worth it, one key consideration is the size of their solar system. Larger systems typically need larger batteries to maximise storage. The table below contains very rough solar self-consumption ratio estimates for a range of popular solar system sizes and energy consumption levels. 

Why solar battery size is important

Choosing the right solar battery size is crucial if you want to get the most out of your solar system. While it’s just one factor to consider, it can make a big difference.

If your battery is too small, you might not have enough energy stored for when the sun isn’t shining, forcing you to rely on grid power. On the flip side, if your battery is too big, you could end up with unused storage, meaning you pay more upfront without any extra benefit.

What is the average solar battery system size in Australia?

In Australia, a typical solar setup combines an 8kW solar panel system with a 10kWh battery. This combination strikes a good balance between energy production and storage, helping you reduce your reliance on the grid and cut electricity costs.

Need more storage? Upgrading to a 15kWh battery can give you extra capacity to handle higher energy use at night or provide backup power during outages.

Top tip: Solar batteries are modular, so you can start with a smaller battery and add more storage later if necessary.

How to calculate what size solar battery you need

To calculate your average daily energy use, simply divide your monthly electricity bill by 30 to get the average for each day. You can also use an online solar battery calculator to help figure out the right battery size for your needs, based on your solar panel system and roof size.

Start by estimating your daily energy consumption. If you have an energy monitor, you can use that. Otherwise, check your monthly bill and divide it by the number of days in the month.

Here’s how it looks:

Average daily consumption = monthly bill ÷ 30 days

Once you know your average daily consumption, you can use a solar battery calculator to determine the ideal size for your solar system and battery. These calculators take into account your daily energy use, solar system size, and roof space to recommend the best battery size for reducing your reliance on the grid.

How many solar batteries does your system need?

Most homes typically use 2 to 3 solar batteries, but the number of batteries you need depends on your energy usage, the reason you want a battery, and the size of your solar system.

The type of battery you choose also affects how many you need. There are two main types: lead-acid and lithium-ion.

DoD stands for Depth of Discharge, which is the amount of energy used from the battery. You don’t want to fully discharge your battery, as this can shorten its lifespan. Different battery types have different DoD levels, which impacts how much energy they can store and how long they last.

Lead-acid batteries have a DoD of 50%, while lithium-ion batteries have a DoD of 80%. This means that with a higher DoD, lithium-ion batteries store more energy, so you'll need fewer of them compared to lead-acid batteries.

Ready to upgrade your solar battery?

While Compare Energy doesn't sell solar batteries, we can certainly recommend solar energy plans in your area that connect you to the right options for optimising your energy bills. Give our team a call on 1300 790 106 and we'll talk you through the switch to solar energy.