Solar batteries: What you should know

Solar battery storage is an easy way to store electricity that you can then use later as required, rather than sending unused power back to the grid. This gives you a reliable cache of solar-generated power to fall back on during the night or on dark and cloudy days.

Ultimately, solar energy storage systems work on the same principle as other rechargeable batteries.

The different types of solar batteries include lead-acid batteries, lithium-ion batteries and liquid ‘flow’ batteries. Which solar battery is appropriate for your solar system will depend on your budget and energy needs.

• Lead-acid batteries. One of the older and more common types of solar batteries, lead-acid batteries are cheaper than most on the market. However, they’re also slow to charge, require regular maintenance, are bulkier than other batteries and don’t last as long.
• Lithium-ion batteries. In recent years, lithium-ion batteries have begun to overtake lead-acid batteries due to their longer lifespan and greater storage capacity in comparison to their size. While still more expensive than lead-acid batteries, they have recently become more affordable.
• Liquid ‘flow’ batteries. Flow batteries (also known as redox flow batteries) use liquids to store energy. They’re easily maintained, fire resistant and the longest-lasting type of solar battery, but they’re the most expensive and don’t generally store as much energy as lithium-ion batteries.¹

Solar batteries work by capturing and storing the surplus electricity generated by your solar panels during the day. The batteries use an inverter to turn raw power generated from solar panels (a direct current) into electricity that can be used in your home (an alternating current).² The inverter then directs any unused excess energy into your batteries during the day.

When the sun goes down and the solar panels stop producing power, your inverter will ‘turn around’ and energy can be drawn from your solar batteries to power your appliances as you need it. Inverters typically only need to be replaced every 10 to 15 years.¹

Once your batteries are fully charged, you can send excess power to the grid. Your inverter will flip to sending additional power to the local grid until you adjust the settings and draw on your own battery power. Otherwise, this excess power could be ‘lost’. Depending on your solar system and batteries, you might be able to adjust your settings in real time to control a few things. For example, you might want to change:

• Where the generated solar energy is sent (either to your home battery storage or to the local grid).
• The solar energy usage from your batteries during the day – it can be useful to set a cap on your daytime solar energy usage to ensure you have enough to last through the night.

There are numerous benefits to investing in a solar battery storage system such as the ability to harness more solar energy and lower your environmental impact. A solar battery storage system can be a big investment, so it’s important to weigh up the following benefits to decide if it’s right for you:

• Harness more solar energy. By storing solar energy, you can harness even more solar power from the sun through your solar photovoltaic (PV) system. This means you have greater energy independence and need less electricity from the energy grid, which can help you reduce your power bills.
• Off-grid systems can work during blackouts. If your solar battery inverter is off-grid, you can potentially use the backup power stored in your battery during a blackout or other power outage.
• Take advantage of solar feed-in tariffs. Solar feed-in tariffs are the rate credited to you by your retailer for the electricity you generate from your solar panels and feed to the grid (which is tracked by a solar smart meter). This means homeowners and businesses can receive electricity bill credits even with a solar battery by sending excess solar power back to the grid. Additionally, if you’re in New South Wales or South Australia, the two-way charge fee (known as the sun tax) means a battery may help you avoid solar export charges during the day and attract better solar feed-in tariffs at night.³
• Lower your environmental impact. Solar energy is a growing source of renewable energy that helps reduce Australia’s carbon footprint. It’s a form of clean energy that allows us to move away from those sources that release large amounts of greenhouse gas emissions such as fossil fuels. By investing in a solar battery storage system, you can reduce your individual environmental impact.
• Option to join a Virtual Power Plant (VPP). If you have a solar battery, you may have eligibility to join a VPP and join a network of connected solar batteries. This means your battery may be drawn on by the VPP during peak demand times to help stabilise the grid. By joining a VPP, you could receive incentives such as a discount on your electricity bills.

Whether solar batteries are worth it will depend on your individual circumstances, your budget, the size of your system and how much electricity your household uses. However, in general, solar storage batteries can help you get more out of your solar panels and lower your energy bills – but there are costs to consider.

In Australia, a home solar system can pay itself off in 7 to 9 years, or even as quickly as 3 to 5 years if you receive a solar photovoltaic (PV) rebate from your state or territory government to help reduce costs.⁴ If you also purchase a solar battery, your payback period will increase; however, a new battery with a new solar system will have a lesser payback period compared to adding a new battery to an existing system.⁵

The cost of solar battery systems and battery installation for Australian households and small businesses will vary based on the type of battery and its size. However, on average, solar batteries cost $10,000 to $13,000 for a typical Australian home.⁶
Thanks to the government’s Cheaper Home Batteries Program, the upfront price of batteries can be significantly reduced by 30% if they are small-scale battery systems of between 5 kilowatt-hours (kWh) and 100 kWh.⁷

As a battery owner, you should also check for potential rebates on your solar power system in your state or territory and potential interest-free loans to help reduce upfront costs.

In Australia, most solar battery home systems will last about 7 to 15 years.⁸ However, different solar batteries will last for different lengths of time, depending on factors such as the type of battery, your local climate conditions, your usage rates and where it’s installed.

While solar batteries do eventually die, proper maintenance and use can help prevent your system from needing a replacement battery before its expected life cycle ends.

Most Australian households use a 5 kilowatt-hour (kWh) to 13 kWh solar battery.⁹ But when deciding on the right solar battery size, it’s important to choose one that matches the output of your solar panels and the amount of power your home uses – not just the biggest battery that you can get. Small homes or single-person households may only require a small solar battery, while someone with a large family or someone who is looking to become less reliant on the electricity grid would require a larger battery capacity.

You should contact a professional solar installer to assess what system size and type of solar battery bank best suits your energy goals.

Yes, most solar batteries for houses and businesses have a warranty. A solar battery warranty can last for a few years, although the length of time may differ between manufacturers. It’s important you understand what’s covered by your warranty and what you need to do so your solar inverter and battery last as long as possible.

Yes, it is possible to go off-grid by using a solar battery system at your home – but the process is difficult. To go off-grid, you will need to ensure that:

• The solar panels are generating enough power to meet your needs.
• You have the right size solar system.
• You have the relevant inverter capability to store multiple batteries.
• You can store enough power for periods without any sun (e.g. rainy days) via your batteries.
• A back-up source of power is available (e.g. a diesel fuelled generator).

If you don’t have the above, you’ll likely still require a connection to the local energy grid so you can draw electricity from it in case you run out of solar power from your batteries.