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Can You Add a Battery to an Existing Solar System?

You’ve had solar panels on your roof for a few years now. Your energy bills have gone down, and you feel good about your environmental footprint. But lately, you’ve been wondering: Could I be saving more?

With feed-in tariffs shrinking and energy prices creeping up, adding a battery to your existing solar system might be the smartest upgrade you make this year. Whether you're motivated by savings, self-sufficiency, or the occasional blackout, this guide walks you through everything you need to know about solar battery storage.

Key Takeaways:

  • Adding a battery to your solar system helps you make the most of your solar energy.
    Instead of exporting excess solar to the grid for a low feed-in tariff, a battery stores it so you can use it in the evening when electricity prices are higher, maximising your savings and self-consumption.

  • The new federal battery rebate can cover up to 30% of your battery costs, making 2025 a great time to upgrade.
    With discounts of up to $3,500 for a 10 kWh battery (and more for larger systems), the subsidy significantly reduces the upfront cost, and could be stacked with some local or council-based incentives if available.

  • Retrofitting a battery is usually straightforward and comes with long-term benefits beyond bill savings.
    Most existing solar systems can be upgraded with a battery, especially those installed more recently. Beyond financial payback, batteries offer blackout protection, enhance home value, and help you future-proof your home for electric vehicles and smarter energy use.

What Exactly Does a Battery Do in a Solar Setup?

When your solar panels generate electricity, you typically have two choices: use the energy immediately or export it to the grid. But when you add a battery to your solar system, you unlock a valuable third option: storing that energy for later use. 

During the day, any excess solar power your system produces charges the battery. Then, at night or during cloudy periods when your panels aren’t generating much power, your home can draw electricity from the battery instead of relying on the grid. 

If your battery includes blackout protection, it can even power your home during outages, keeping the lights on when the grid goes down. By storing and using your own solar energy, you gain greater energy independence and boost your long-term savings.

contemporary home at sunset with rooftop solar panels

When Does It Make Sense to Add a Battery to Your Solar System?

Adding a battery to your solar system is a significant investment, but for many Australian households, it can dramatically boost energy savings, resilience, and independence. While batteries aren’t the right fit for everyone, there are clear scenarios where they make a strong case. Here's when it really makes sense and why:

Your Feed-in Tariff Is Low or Ending

In the early days of solar, some states offered generous feed-in tariffs like Victoria’s Premium Feed-in Tariff (PFiT), which paid up to 66c per kWh of exported solar. But that scheme officially ended on 1 November 2024. Today, most households only earn 5c–10c per kWh when exporting solar to the grid, while paying 30c–45c per kWh to buy electricity back. That’s a huge gap.

Why add a battery:

Rather than exporting your valuable excess solar for a few cents and buying it back later at a premium, a battery lets you store that energy for your own use. This dramatically reduces your electricity bills and makes your solar system far more efficient and financially rewarding.

You’re on a Time-of-Use (TOU) Tariff

If you’re on a TOU tariff, your electricity costs vary depending on the time of day, typically cheapest overnight and most expensive between 4 pm and 9 pm. That means using grid electricity during peak hours can be costly.

Why add a battery:

A battery allows you to shift your energy usage—charging up when power is cheap (or when your solar is generating) and discharging when prices spike. Some advanced batteries, like Tesla Powerwall 3 or Heartbeat, can even predict peak pricing and discharge intelligently to maximise savings.

You Use Most of Your Power at Night

Solar panels generate energy during the day, but what if no one’s home to use it? If you’re working 9 to 5, most of that solar is exported to the grid, and you're forced to buy electricity at peak rates once the sun goes down.

Who does this benefit:

  • Working families who aren’t home during the day

  • Shift workers or night owls

  • EV owners charging overnight

  • Homes using electric heating, cooling, or hot water during evenings

Why add a battery:

A battery captures your unused daytime solar and stores it for use when it matters most, at night. Instead of selling cheap and buying expensive, you use your own clean energy when you need it most.

You Want Blackout Protection

Blackouts are becoming more common due to extreme weather, aging infrastructure, and rising grid instability. If you live in a bushfire-prone area, or just want peace of mind, backup power is increasingly essential.

Why add a battery:

A battery with blackout protection can power key appliances during an outage, keeping your lights on, your fridge running, your devices charged, and even supporting medical equipment. Just be sure to choose a battery with backup functionality, and have your installer configure it to power the circuits that matter most.

You Plan to Stay in Your Home Long-Term

Solar batteries are best suited for homeowners who intend to stay put for several years. Like solar panels, they’re a long-term investment that grows in value the longer you remain in the home.

Why add a battery:

  • Most batteries pay for themselves in 7–10 years

  • Warranties typically cover 10 years of use

  • Staying long-term allows you to fully capitalise on energy savings, especially as electricity prices continue to rise

How Much Does It Cost to Add a Battery to a Solar System?

While battery prices have steadily declined over the past decade, adding a battery to your home solar system is still a major financial decision. The total cost depends on the battery model, storage capacity (kWh), brand, and installation complexity.

Battery Size (kWh)Estimated Total CostExample brands
3 kWhStarts from $4,500 Enphase IQ Battery 3T, Sungrow SBR
5 kWhStarts from $7,500 BYD, Sungrow SBR, LG RESU
6.5 kWhStarts from $9,750 LG RESU, Huawei LUNA2000
10 kWhStarts from $15,000 Tesla Powerwall, Sungrow, BYD
13 kWhStarts from $19,500Tesla Powerwall, SolarEdge Home
15kWhStarts from $22,500SolarEdge Home, Sungrow SBR
18-20 kWhStarts from $27,000 to $30,000Tesla Powerwall (stacked), BYD

What Affects the Total Cost?

Several additional factors can influence the final cost of adding a battery, especially in retrofit scenarios:

  • Switchboard Upgrades

    Older homes may require switchboard upgrades to meet current electrical standards or to safely integrate battery systems.

  • Backup Circuit Installation

    If you want your battery to power critical appliances during a blackout, backup circuits need to be installed. This typically involves isolating selected circuits (e.g. fridge, lighting, Wi-Fi) and configuring the system accordingly.

  • Energy Monitoring Software

    Some battery systems come with integrated apps, while others require optional add-ons for advanced monitoring, automation, or time-of-use optimisation.

How Much Can You Save With A Battery?

Adding a battery isn’t just about peace of mind or energy independence. It can lead to real, long-term savings. While every household is different, here’s a typical example that shows how the maths stacks up.

Let’s run a typical scenario:

  • You have a 6.6kW solar system

  • You’re on a Time-of-Use tariff

  • You use about 18kWh/day, mostly in the evening

  • You add a 13.5kWh Tesla Powerwall 3

Without a battery:

  • You export 60% of your solar for ~5c/kWh

  • You buy power at night for ~35c/kWh

With a battery:

  • You store and use your solar

  • You buy less from the grid only when needed

Estimated savings: ~$1,200–$1,800/year

Payback period: ~7–10 years (faster if prices rise or rebates apply)

Rebates & Incentives for Adding a Battery

Thanks to a new federal solar battery rebate that launched in July 2025, adding a battery to your home or business just got a whole lot more affordable.

Under the program, eligible households, small businesses, and community groups can save up to 30% off the cost of a battery system. That’s a potential rebate of $3,500 for a 10 kWh battery or as much as $17,500 for a 50 kWh battery.

The subsidy applies to systems sized between 5 kWh and 50 kWh. Batteries must be installed with either a new or existing solar system, and they must be VPP-ready, though joining a VPP is optional.

The rebate is also available for multiple properties, making it a great option for landlords or business owners expanding their solar setup. Like the existing federal solar rebate, this new battery subsidy will decrease over time, so acting early means bigger savings.

You may also be able to stack this federal rebate with state-based or local council incentives, depending on where you live. A Clean Energy Council-accredited installer can help you confirm your eligibility for the following:

StateRebate and Loan ProgramsStatusDescription
NSWHousehold Energy Saving UpgradesClosing on 30 June 2025The NSW Government offers a discount when you install a solar battery with your solar system or add one to an existing setup. The discount is applied directly by accredited installers and helps reduce the upfront cost of installing a battery. The NSW battery discount will no longer be available after 30 June 2025. It cannot be combined with the new federal Cheaper Home Batteries Program, which begins on 1 July 2025. However, the NSW's Virtual Power Plant (VPP) incentive will nearly double and can be combined with the federal rebate. If you already have a battery or install one under the new federal program, you may still be eligible for the NSW VPP incentive.
Local Council IncentiveActiveLocal councils, such as Randwick and North Sydney Councils, offer rebates that support solar battery installations for residents, businesses, and apartment blocks within the local area. Some rebates cover up to 10% of the installation cost.
ACTSustainable Household SchemeActiveThis program offers eligible homeowners loans between $2,000 and $15,000 to help cover the cost of installing solar batteries and other energy-efficient home upgrades. From 1 July 2025, new loans will have a 3% fixed interest rate for most households, while concession-card holders will continue to have access to interest-free loans. Loans can be repaid for up to 10 years with no upfront fees.
WAResidential Battery SchemeActiveThe WA Residential Battery Scheme, launching by July 2025, offers eligible Western Australian homeowners rebates of up to $5,000 (for Synergy customers) or $7,500 (for Horizon Power customers). Interest-free loans up to $10,000 are available for low- to middle-income households. The scheme supports the installation of new batteries that can participate in Virtual Power Plants (VPPs).
TASEnergy Save Loan SchemeActiveThe Tasmanian Government's Energy Saver Loan Scheme offers interest-free loans between $500 and $10,000 to eligible homeowners, landlords, small businesses, and not-for-profit organisations. These loans can finance energy-efficient upgrades, including battery storage systems, with repayment terms ranging from one to three years. Brighte administers the scheme and aims to make sustainable energy solutions more accessible across Tasmania.

Can I Add a Battery to My Existing Solar System?

In most cases, you can retrofit a battery to an existing solar setup. However, there are a few important technical and practical factors to consider to ensure a smooth and cost-effective installation.

1. Your Inverter Type

Not all inverters are battery-ready. If you have a non-hybrid inverter, you may need to either:

  • Replace your existing inverter with a hybrid inverter that supports both solar panels and battery charging/discharging; or

  • Install a separate battery inverter, which is often the case with all-in-one systems like the Tesla Powerwall (which includes its own battery inverter).

A qualified installer can inspect your current system and recommend the most compatible and cost-effective solution.

3. The Size of Your Existing Solar System

If your system is relatively small (e.g. less than 3 kW), it might not generate enough excess energy to charge a battery consistently, especially during winter or cloudy periods. In these cases, a battery might not deliver a strong return on investment unless you also expand your solar array.

2. Space and Capacity on Your Switchboard

Battery systems may require new safety equipment, isolators, circuit breakers, or smart meters. Your existing switchboard must have enough space to accommodate these components, and in some cases, additional wiring or upgrades to your main switchboard may be necessary.

4. Your Energy Consumption Pattern

Batteries work best when they’re able to store excess solar energy that would otherwise be exported to the grid. If your household uses most of its electricity during the day (when solar is generated), there may be less surplus energy to store. On the other hand, if you tend to use more power at night—or want blackout protection—adding a battery could still be a worthwhile investment.

Bonus Tip: If you’re upgrading your system or planning future electrification (e.g. adding an EV, heat pump, or induction cooking), consider scaling your solar and battery setup accordingly so it meets your future energy needs, not just today’s usage.

Which Battery Should You Choose?

Not all home batteries are created equal, and the right one for your needs depends on your energy usage, solar setup, and long-term goals. Here’s what to consider when comparing options:

FeatureWhat It Means
Capacity (kWh)The total amount of energy your battery can store. Larger systems store more solar.
Power OutputHow much energy the battery can deliver at once. Important for running appliances during outages.
WarrantyLook for batteries with at least 10 years of warranty or guaranteed >70% capacity retention after 10 years.
Backup SupportSome batteries can power your home during a blackout; others can’t. Always confirm blackout capabilities.
Smart FeaturesIncludes app-based control, forecast-based charging, energy optimisation, and VPP-readiness.

Pro Tip: Think beyond just storing power. If you want your battery to optimise your home’s energy use, support blackout protection, and participate in Virtual Power Plants, look for a battery that offers advanced energy management features.

Our Recommendation: The 1KOMMA5° Battery

If you're looking to retrofit a battery to your existing solar system, the 1KOMMA5° Home Battery is purpose-built for the job. Designed with flexibility, durability, and intelligence in mind, it’s one of the best retrofit-compatible batteries available in Australia today.

  • Engineered in Germany, Ready for Australian Homes

    Designed and tested in our Berlin tech lab, the 1KOMMA5° Battery has been engineered for performance and reliability in Australia’s demanding climate.
    Its IP65-rated LFP (lithium iron phosphate) chemistry offers safe, stable, and long-lasting performance, making it a perfect match for homes looking to upgrade their solar setup with confidence.

  • Retrofit-Friendly, Stackable Design

    Already have solar? No problem. The modular design of the 1KOMMA5° Battery makes it ideal for retrofit installations.
    With flexible sizing from 8.2 kWh to 37.8 kWh and charging power up to 20.16 kW, you can start small and expand later—without overhauling your existing solar system. Whether you're topping up a smaller solar array or future-proofing a growing household, it adapts to your needs.

modern house connected to a grid

  • Microcycling for VPP Participation

    Retrofitting isn’t just about storing energy. It’s about using it wisely.
    The 1KOMMA5° Battery is optimised for microcycling (frequent small charge and discharge cycles), making it VPP-ready. That means you can take part in emerging virtual power plant programs and earn rewards, without changing your current solar setup.

  • Seamless Blackout Protection

    When the grid goes down, your battery steps up.
    With built-in backup functionality, the 1KOMMA5° Battery can power essential appliances during an outage, adding resilience to your home without needing a full system redesign.

  • 12-Year Warranty

    Retrofitting should be a long-term upgrade, not a short-term fix. That’s why the 1KOMMA5° Battery comes with a 12-year product warranty, giving you confidence that your investment will deliver reliable performance for years to come.

  • Heartbeat AI-Ready

    Already have solar but want smarter energy control? The 1KOMMA5° Battery is ready for Heartbeat AI, our intelligent energy manager launching soon.
    It will automatically analyse your household usage, solar generation, weather forecasts, and electricity market signals to optimise when and how your battery is used so you can get even more from your system without lifting a finger.

The Long-Term Benefits of Adding a Battery

modern house connected to a grid

Installing a battery isn’t just a short-term way to reduce your power bills. It’s a future-proof investment in your home’s energy resilience and value. Here’s how it pays off:

  • Protection from Rising Power Prices
    Store your excess solar and avoid buying expensive grid electricity during peak times.

  • Blackout Protection
    Keep your essential appliances running during outages (when paired with a battery that supports backup).

  • EV-Ready Home
    Batteries help smooth out your energy load, making EV charging at home more affordable and sustainable.

  • Reduced Grid Reliance
    Use more of your own solar and rely less on fossil fuel-generated electricity.

  • Improved Property Value & Energy Rating
    Homes with solar and battery systems are increasingly attractive to buyers seeking lower energy costs and sustainability.

What Happens During A Battery Retrofit Installation?

Retrofit battery installations are typically completed in 1 to 2 days, depending on your home’s electrical setup and whether it's a new install or retrofit. If you choose 1KOMMA5° for your battery and installation, here’s the level of service you can expect:

  1. Pre-Installation Site Inspection
    A qualified 1KOMMA5° electrician will assess your existing solar system, electricity usage, switchboard capacity, and the best location for your battery (wall or ground-mounted).

  2. Installation Day

    Our accredited technicians take care of the full installation process, including:

    • Securely mounting the battery unit

    • Connecting it to your solar inverter or main switchboard

    • Installing or upgrading safety switches and protections

    • Thorough system testing and commissioning

  3. Monitoring and Setup
    To wrap up the process, we will guide you through the battery monitoring app, where you can track real-time charge levels, energy use, solar production, and grid interaction.

1KOMMA5° solar experts take care of every step, from planning and product selection to installation and support. Moreover, we offer access to trusted, best-value and premium solar products. If you're looking for a battery that adapts as your energy needs change, the 1KOMMA5° Battery is one of the most retrofit-friendly options available.

Why Choose 1KOMMA5° for Your Battery Retrofit?

Retrofitting a battery to your solar system is a big step, but with 1KOMMA5°, it doesn’t have to be complicated. As Australia’s one-stop-shop for New Energy solutions, we’re here to guide you from A to Z. Whether you're just starting your energy journey or ready to maximise your existing system, we’ve got the expertise, tools, and support to get you there.

Here’s why thousands of Australians have chosen 1KOMMA5°:

  • Australia’s Complete New Energy Solution
    From solar panels to batteries, EV chargers and heat pumps. We offer a fully integrated approach that helps you achieve true energy independence, now and into the future.

  • Tailored Design & Product Advice
    Our team creates custom solutions based on your energy usage, home setup, and future goals. We don’t push products, we recommend what works best for you.

  • Trusted Nationwide Installer
    With local teams across QLD, NSW, VIC, ACT, and SA, we’re a Top 5 National Installer backed by deep regional knowledge and hands-on expertise.

  • 1K5° Care: Support That Lasts
    Enjoy peace of mind with our exclusive 1K5° Care program:
    • 30-Year Workmanship Guarantee
    • Annual Energy Plan for ongoing savings
    • Fast Australian-based support
    • 90-Day System Health Check

Conclusion: Should You Retrofit a Battery to Your Solar System?

If you’ve already invested in solar, you’re halfway there. A battery doesn’t just help you store power. It helps you use your solar when it actually matters: at night, during peak pricing, or when the grid goes down. That’s where the real savings and peace of mind come in.

Retrofitting a battery makes even more sense now, with the new federal rebate covering up to 30% of the cost. You don’t need to rebuild your system. You don’t need to be tech-savvy. You just need a system that works harder for you, and that’s exactly what a battery does.

This isn’t about jumping on a trend. It’s about making your home more future-proof, more self-reliant, and frankly, a lot smarter.

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