Wondering if solar panels still generate electricity on cold, cloudy or rainy winter days? We answer the top questions about using solar panels in winter.
Solar Batteries
How do solar batteries work and are they worth it?
Solar batteries: what they are, how they work, and how much money can they save you.
Solar panels have become a familiar sight on rooftops across Australia, helping households generate renewable electricity and reduce power bills. But solar panels alone only produce electricity during daylight hours. For many households, most energy is used in the evening - when the sun has already set.
This is where solar batteries come in. By storing excess solar energy generated during the day, a solar battery allows you to use your own renewable electricity at night or during cloudy periods. As energy prices rise and feed-in tariffs fall, more Australians are considering battery storage as a way to maximise the value of their solar systems.
But how exactly do solar batteries work, and are they worth the investment? Here's what homeowners should know before installing one.
More: What to consider when upgrading your solar power system
What is a solar battery?
A solar battery is an energy storage system designed to store excess electricity generated by rooftop solar panels. It allows the household to use that electricity at a time when the solar system is not producing enough (for example, in poor weather) or at night.
Depending on the type of battery, you could also use stored energy during a grid outage or blackout, or even to power an electric vehicle.
How do solar batteries work?
A solar battery works as part of a broader home energy system that includes solar panels, an inverter and your household electrical circuits.
Here's how the process typically works.
- Solar panels generate electricity - your rooftop solar panels convert sunlight into direct current (DC) electricity throughout the day. The more sunlight they receive, the more electricity they generate.
- The inverter converts electricity - the system's inverter converts the DC electricity produced by solar panels into usable alternating current (AC) electricity, which most household appliances run on.
- Your home uses solar power first - the solar energy generated during the day is used to power lighting, appliances, air conditioners and electronics.
- Excess electricity charges the battery - if your solar panels produce more electricity than your home is using, the surplus energy charges the solar battery rather than being exported to the grid.
- Stored electricity powers your home later - when solar panels stop generating electricity (typically in the evening or overnight), your home can draw power from the battery instead of the grid.
If the solar battery fully discharges (that is, runs out of power), your household will automatically switch back to using electricity from the grid.
More: How does home solar power work? Solar panels & batteries explained
A solar battery can power your home overnight with energy stored from your solar panels.
Do solar batteries work during blackouts?
With blackout protection, you could keep your lights on in the event of a power outage using the electricity stored in your battery.
There are two types of blackout protection:
- Whole-of-home backup batteries power everything in the house during a blackout, but will drain quicker – especially if you continue to use power guzzlers such as air conditioners.
- Essential load backup helps your battery charge last longer by isolating certain circuits to power the essentials only, such as lighting and fridges.
Not all systems automatically include this feature. If blackout protection is important to you, make sure you discuss this with an accredited solar installer when working out the right solar battery solution for your needs.
More: Do solar batteries work during a blackout?
How long do solar batteries last?
Solar batteries degrade gradually over time, meaning they store slightly less energy each year.
Most modern lithium-ion batteries:
- last around 10 to 15 years
- are rated for around 6,000 charge cycles (full charge and discharge of the battery)
- include warranties of approximately 10 years.
Even after the warranty period, many batteries continue to function, but with reduced capacity.
Solar batteries are sized in kilowatt-hours (kWh) to represent how much electricity they can store.
What size solar battery do I need?
Solar batteries are sized in kilowatt-hours (kWh), which represents how much electricity they can store.
Batteries usually have a storage capacity rating and a useable capacity rating:
- Storage capacity (nominal capacity) - the total energy the battery can physically store
- Usable capacity - the portion of that energy you can actually use in practice.
The difference exists to protect the battery's lifespan and safety. When considering a solar battery, the useable capacity will help you determine what size battery is best suited to your useage.
Your ideal battery size depends on several factors, including:
- household electricity consumption
- size of your solar panel system
- energy usage patterns
- your budget.
What type of solar battery should I get?
There are several different battery technologies used in residential solar systems.
Lithium-ion batteries
Most modern home batteries use lithium-ion technology, similar to the batteries used in electric vehicles and smartphones.
Advantages include a high energy density, long lifespan, high efficiency, and compact size. Many current home batteries use lithium iron phosphate (LFP) chemistry, which is known for its safety and durability.
For most residential systems they are the best option, so many installers (like RACV Solar) only offer li-ion batteries.
More: Guide to Tesla batteries for solar
Lead-acid batteries
Lead-acid batteries were among the earliest technologies used in off-grid solar systems. Until recently, most home batteries were flooded lead-acid; they have since been replaced by sealed lead acid (SLA) batteries for additional safety.
They are typically cheaper upfront, but are bulkier with a shorter lifespan and lower efficiency. Because of these drawbacks, they are mostly used in off-grid solar systems.
Flow batteries
Flow batteries store energy in liquid electrolytes contained in separate tanks.
They offer advantages such as a long lifespan, deep discharge capability, high safety level and easy maintenance. However, they are currently rare in residential settings due to higher costs and limited availability.
An accredited installer can help you decide which battery is right for your household.
How much do solar batteries cost?
The cost of solar batteries varies depending on the size, brand and installation complexity.
In Australia, homeowners typically pay around $1,000 to $1,200 per kWh of battery storage installed, although prices are gradually falling. For example, a 5kWh battery may cost roughly $5,000-$6,000.
Prices are generally lower when the battery is installed at the same time as a new solar panel system rather than retrofitted later.
Solar batteries can also help households save on energy bills.
Will I get a rebate on my solar battery?
You can reduce the upfront cost of installing an eligible solar battery by around 30 per cent with the government's Cheaper Home Batteries Program. The solar battery must:
- use a CEC-approved battery
- have a battery capacity between 5 kWh and 100 kWh (rebate applies to the first 50 kWh)
- be installed by an SAA-approved installer like RACV Solar
- be installed between 6 April 2025 and 2030.
Are solar batteries worth it?
Whether a solar battery is worth the investment depends on several factors, including electricity prices, solar generation and household usage patterns.
Solar batteries tend to be most worthwhile if you:
- have a large solar system that generates surplus electricity
- use significant power in the evening
- want backup power during outages
- plan to stay in your home long enough to recoup the investment.
Lower electricity bills
A battery allows you to use more of your own solar power rather than buying electricity from the grid.
This is particularly valuable because grid electricity can cost 30–45 cents per kWh, while many solar feed-in tariffs pay only 2–8 cents per kWh for exported energy. So, by storing energy instead of exporting it, households can capture more value from their solar system.
Greater energy independence
With a solar battery, your home becomes less reliant on the electricity grid. This can provide greater protection against rising electricity prices, power outages, and peak electricity demand periods.
Environmental benefits
Solar batteries help maximise renewable energy usage by storing clean electricity that would otherwise be exported or wasted. This can reduce reliance on fossil fuel-generated electricity from the grid.
Potential participation in Virtual Power Plants
Some battery owners can join Virtual Power Plants (VPPs), where network operators coordinate many household batteries to support the electricity grid. Participants may even receive financial incentives for allowing their battery to supply energy during peak demand.
