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8.25kW SE Home Hub Inverter with 9.7kWh SE Battery and SE Backup Interface and Essential Circuit Sub Board installed for a 3D Energy customer on a concrete wall under the house

How to Add a Battery to an Existing Solar Power System

If you’re looking to boost your energy storage capacity, adding a battery to your existing solar panel system is an excellent option to consider. It can provide several benefits, such as backup power during grid outages, reduced reliance on the grid utilising the battery storage for overnight self-consumption, increased efficiency and reliability of your solar system, and a reduced carbon footprint.

This blog post will offer you a detailed guide on how to add a battery to your current solar system setup. We’ll also cover essential factors to consider when making this decision, including the benefits that adding a battery can provide. By understanding the process of adding a battery, you can make an informed decision that aligns with your energy needs and goals.

Why Would You Need to Add a Battery to Your Solar Power System?

Investing in a battery energy storage system is a smart choice for homeowners looking to reduce the costly imported grid power at night time, have peace of mind that even during a grid outage that your house will still have power supply to your essential circuits and increase the value of their home asset.

With a sufficient amount of stored energy, a solar battery can power your home for hours or even days, depending on your energy usage and PV capacity.

By adding a battery to your existing solar PV system, you are storing the solar energy produced during daylight hours ready for self-consumption overnight and additional capacity to help power more appliances and devices for extended periods without having to import grid power.

This means you can enjoy a reliable source of electricity even during outages or emergencies.

Benefits of Adding an Additional Battery or Battery Storage Modules

Adding additional batteries or additional battery storage modules to your existing solar & storage system can provide several benefits, including:

Increased stored energy: Adding additional battery capacity to your solar system provides more stored energy for longer backup power during outages, giving you peace of mind.

Reduced reliance on the grid: Adding additional battery capacity to your solar system reduces reliance on the grid, increasing self-consumption and saving you money on your electricity bills.

Increased efficiency and reliability: Adding additional battery capacity to your solar system can increase the efficiency and reliability of your system. With more stored energy, you’ll be able to power your home for longer periods of time, reducing the need for grid electricity.

Reduced carbon footprint: Adding additional battery capacity reduces your carbon footprint and contributes to a more sustainable future by reducing reliance on the grid and using stored solar energy. Lithium-ion technology, used in many solar batteries, is environmentally friendly and easy to recycle.

DC Coupled vs. AC Coupled Battery Storage Systems

When considering adding another battery to your solar system, it’s essential to understand the difference between DC coupled and AC coupled battery storage systems.

DC coupled storage systems involve connecting the battery directly to the DC side of the multi-mode “hybrid” inverter, which allows for charging and discharging the battery with minimal energy loss. This results in greater energy storage for your money. The other benefit of DC coupled storage systems is that when the grid is down and sun is shining on the solar panels then the solar system continues to operate and supply power to your essential circuits and also continues to charge the battery. The battery is then discharged at night and this scenario can continue for many days with the inverter in “off grid” backup mode. As soon as the grid is detected once again by the hybrid inverter’s energy meter then it automatically changes back to normal operation mode. DC coupled storage systems require the correct type of hybrid inverter paired with the correct type of battery to function.

In contrast, AC coupled battery storage systems are connected directly to the switchboard and rely on the solar power from the existing grid connected solar system to charge the battery. In some cases with AC coupled storage systems, the storage inverter cannot control or make the existing grid connected inverter operate when there’s a grid outage resulting in no backup supply. 

While AC coupled storage systems are less efficient due to more energy loss during the multiple conversion steps involved, it’s still a cost-effective and straightforward option, as it’s sometimes less expensive and depending on the existing inverter it’s sometimes easier to install or add to an existing solar system.

Ultimately, the decision of which coupling type to choose depends on your personal preference and 3D Energy can provide assistance with this. To help make this decision easier, we’ve compiled a list of pros and cons for each option:

DC Coupled Storage Systems:


  • More efficient than AC coupled systems
  • Less energy conversion losses during charging and discharging
  • Allows for more precise battery monitoring and control through the one hybrid inverter
  • Suitable for larger battery systems
  • One hybrid inverter can be installed with the solar array and battery connected to it
  • Easy to not exceed maximum permissible inverter size limits where only one hybrid inverter is installed
  • Able to claim more STC rebate with a larger solar PV array upon installation
  • One hybrid inverter can have solar panels and battery connected to it
  • Great for new installations


  • More technically complex and requires specialised expertise in designing the system


AC Coupled Storage System:


  • Easy to retrofit to an existing solar system as long as there’s a large enough array with surplus solar power to charge the battery
  • Suitable for smaller battery systems where overnight consumption is reasonably small


  • Less efficient, greater amount of energy conversions compared with a DC coupled system, more power loss during charging. 
  • Less precise self-consumption, battery and solar production monitoring using multiple monitoring systems from different manufacturers
  • Sometimes unable to control the existing inverter to operate during grid outages for backup supply due to inverters from different manufacturers
  • Local Distribution Network Service Provider’s have total inverter capacity size limits set (existing solar + new battery storage inverters must not exceed the total inverter capacity limit on each site).   

Rebates and Incentives

Unfortunately there are currently no rebates from both the Queensland or Federal Governments to install a battery storage system, with the Federal Government rebate currently only applying to solar PV systems. 

However, during the recent 2023 Federal Government Budget announcement, Australia’s clean energy future is amongst the 2023-2024 Budget winners. Rooftop solar and household batteries will get a big boost, with over $1.6 billion in support to small businesses, households, landlords and social housing for energy upgrades, encouraging energy efficiency and electrification. Rooftop solar and household batteries are eligible under these new programs with new policies to be introduced so watch this space.

How to Add a Battery to an Existing Solar System

When it comes to the actual installation of your battery, we recommend getting in contact with 3D Energy who are Accredited Clean Energy Council Electricians holding Accreditations such as Solar PV Design & Install with the Storage Endorsement. This will ensure your battery is installed correctly to manufacturers specifications, is compliant with industry standards, operates correctly and safely.

For your interest, however, we have prepared a short step-by-step guide on how 3D Energy Accredited Electricians will go about designing and installing your new battery onto your existing solar panel system.

  1. Determine loads: You should identify the loads in the house or business so a suitable battery storage system can be designed. Loads such as ducted air conditioning, EV charging, electric hot water units, pool pumps and pool heating draw large amounts of power and if possible they should be run during daylight hours when the solar system is operating but we all understand that air conditioning units can run outside of these desired times for comfort.
  2. Existing solar system: We will need to know what make and model the inverter is and the solar PV system size connected to this inverter to determine network inverter size limits.
  3. Electricity bill: Analysing the information contained in the electricity bill is crucial to designing a suitable storage system. When you have an existing solar system (without it access to online monitoring) we can calculate an approximate daily amount of surplus solar power being fed to the grid which can be redirected into charging a new battery or if you don’t have an existing solar system then it’s possible to design a large enough DC coupled solar PV & Battery Storage System to cater for all existing and future loads
  4. Back up function: Essential circuits (lighting, power & small air con units) can be transferred to the back up supply of the inverter. This involves reconfiguring wiring or adding a new backup switchboard for these circuits        
  5. Install a Hybrid inverter or AC coupled storage inverter system: To add a battery to your current solar power system, you will either need to replace your existing grid connected inverter with a hybrid inverter that can manage both your solar panels and your battery or install a separate AC coupled storage inverter system. 
  6. Choose the right battery: Next, you will need to choose the best storage battery for your needs and ensure that it’s compatible and supported to work with the chosen hybrid inverter. Lithium-ion batteries are the most commonly used for household storage systems because they have a longer lifespan, require little maintenance, and are more efficient than other types of batteries.
  7. Install the battery: Once you have selected your battery, you can connect it to the hybrid inverter and it is charged using DC solar power. The hybrid inverter will then convert the DC power into AC power (from both the solar panels and battery), which can be used to power your home or business.
  8. Monitor your system: It is important to monitor your battery energy storage system to ensure it is functioning properly. Check the battery charge level regularly to ensure it is charging and discharging as expected. Additionally, make sure to keep the battery clean and free of debris to prevent any damage or malfunction.

Install your new solar battery today

By adding another battery to your existing solar battery storage system, you can ensure that your home or business will continue to have access to electricity during outages or emergencies. With an increased storage capacity, you can power more appliances and devices for extended periods, giving you peace of mind and the assurance that you won’t be left in the dark.

Moreover, adding another battery to your solar battery storage system not only increases backup power during outages but also helps reduce reliance on the grid, resulting in lower electricity bills. By using more stored solar energy, less electricity from the grid is consumed, leading to a decrease in the amount charged for the electricity used. This way, you can save money on your energy bills and make your investment in solar energy even more cost-effective over time.

Here at 3D Energy, we are dedicated to providing homeowners and businesses in Brisbane with high-quality solar battery storage systems. Our experienced and knowledgeable team can help you choose the best solar battery for your existing solar system and provide expert installation services.

As a trusted and reliable partner in the solar energy industry, we take pride in our local presence and commitment to supporting the local community. Our personalised solutions and ongoing support ensure that you get the most out of your solar energy system. So, if you’re considering adding a battery to your existing solar system, reach out to us for a free consultation. Our team of experts will guide you through the process and provide you with reliable and efficient solar power for years to come.

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