What is a home battery?

Once upon a time, household batteries were just what you reached for to revive your TV remote or put a stop to those pesky smoke alarm beeps. Today though, they’re an important part of a much bigger picture – the transition to a more sustainable future. Now that more than 4 million households and small businesses in Australia have installed rooftop solar, home solar batteries are becoming increasingly popular. Here’s what you need to know before adding a home battery to your solar plans or upgrading your existing system.

What is a battery?

Also known as a battery energy storage system (BESS), a home battery captures electrical energy so you can use it later. You could say it’s the energy equivalent of a piggy bank that takes care of your spare change until you need it. Picture an upscaled version of the power bank that recharges your phone when you’re out and about, or solar powered lights that hold onto energy from the sun to use later when it’s dark.

What are the benefits of a home power storage battery?

Having a home battery increases your energy independence, because you won’t have to rely as much on the main electricity grid. For example, it might mean you have a backup source of power in a blackout. Even better, it may save you money because you can conserve energy that you’ve generated for free (or bought from the grid at cheaper times of day) then use it during the peak times when prices are higher. That way excess solar energy you don’t use during the day won’t be going to waste.

Another good reason to invest in a battery is to access the financial benefits of being part of a Virtual Power Plant (VPP). These small-scale networks are formed from household solar systems and batteries, connected and coordinated remotely through smart technology. VPP operators can effectively manage supply and demand to create a more stable grid than traditional power plants.

Find out more about the Akai Energy Solar Power System or Tesla Powerwall 3.

How does charging and discharging work?

Charging and discharging are the processes home batteries use to store and release energy. Solar panels often generate more energy than your home can use immediately, so this is converted and chemically stored in the battery during the charging phase. Once the battery is full, the excess energy feeds back into the grid. But at times when the solar panels can’t generate enough – like when it’s cloudy or dark outside – the battery enters its discharging phase.

This is when the stored energy is released and converted back into electricity to power your home.

Do you need solar panels to get a home battery?

As a renewable energy policy, government financial incentives specify installing a battery with new solar panels or adding a battery to an existing solar system. That doesn’t mean you can’t benefit from a standalone home battery. If your energy plan includes time-of-use tariffs, you could charge the battery from the grid during off-peak hours and then discharge at peak times to save on your energy spend. Plus, there’s the advantage of blackout protection. But for the biggest bill savings and environmental wins, you’re going to want solar panels and a battery.

Understanding solar battery capacity

Electricity consumption is measured in kilowatt-hours (kWh). This is the amount of energy a one-kilowatt appliance uses up in one hour. So, if a battery has a capacity of 10kWh, it could ideally power a 10kW appliance for an hour, or a 1kW one for 10 hours (for example, appliances such as dishwashers, microwaves and washing machines each need about 1.5kW of power). But the true capacity of a battery is limited by its Depth of Discharge (DoD) – how much of the energy can be safely used without causing damage.

This varies depending on battery type – DoD is much higher for lithium-ion batteries (usually 80 per cent or higher) than for older-style lead-acid batteries (30–50 per cent).