AC vs. DC-coupled Solar Batteries: Which is Better?⚡2025
Posted 20 Mar
Posted 20 Mar
If you’re someone who has ever looked into getting a battery for your home or business, you’ve probably heard the phrase “AC-coupled” or “DC-coupled” battery storage. What does this actually mean to someone who is not an electrician?
Well you’ve come to the right place. Let’s understand what in the world these installers are talking about and help you make better decisions into choosing the right battery setup for your property.
Firstly, if you haven’t already, go check out our AC vs. DC article to understand what they are more in-depth.
When your solar system creates energy, it is in the form of Direct Current (DC). However, your home and its appliances run on Alternating Current (AC), so solar can’t just directly power your home as it needs to be converted. In comes your inverter, which is responsible for converting the DC power from the solar and inverting it to AC power to be used.
When a battery comes into the mix, there are different configurations that installers opt for, based on your property’s requirements and budget that affect where and how the battery is integrated into your system. Installers may opt for a battery in an AC-coupled configuration for advantages like better compatibility, or a DC-coupled configuration for higher overall efficiency.
Here are the key differences between AC and DC-coupled batteries.
| AC-Coupled Battery | DC-Coupled Battery | |
| Recommended for | Retrofitting existing systems | New solar systems |
| Efficiency | Less efficient with multiple conversions between AC and DC | More efficient with limited AC and DC conversions. |
| Complexity | This will depend on site conditions | |
| Inverter required | Battery Inverter | Hybrid Inverter |
| Design | Design may require a battery-ready inverter or related equipment like a backup gateway. | Design may require new, additional or replacement of solar depending on existing system setup. |
| Cost | This will depend on site conditions | |
Using the diagram as a reference, the solar system is its own system, producing solar and powering the home and feeding excess into the grid. In this configuration, a battery is integrated by AC-coupling a battery with a built-in inverter which is responsible for its own DC and AC conversion.
The existing grid-type inverter (non-hybrid) is designed to take that solar energy and convert it to AC for home usage, and does not supply the battery with DC power. Instead, the battery is fed excess energy in the form of AC, which the built-in inverter, converts it to DC to be stored and back to AC when the home needs it.
This configuration is typically chosen for existing solar systems as an inverter already exists which is usually a ‘non-hybrid’ or ‘not battery ready’ which means a battery cannot be directly integrated like a DC-coupled system. AC-coupled systems allow batteries to be integrated and operational, independent of your solar system for easier installation and broader compatibility for retrofitting.
Better for Retrofitting: For homes with existing solar systems, AC-coupled are generally better options than DC-coupled batteries due to compatibility requirements.
Flexibility: With the ability to retrofit to a range of solar systems of all ages, AC-coupled batteries also offer flexible installation location options, as well as a broader range of compatible inverters.
Independence: As solar and battery systems are separate in an AC-coupled design, your battery can be charged from both solar and from the grid.
Reduced energy efficiency: Because the energy is converted between AC and DC more times than a DC-coupled battery, it means the system will be less efficient. However, when it comes to day to day performance, this efficiency loss is minimal and shouldn’t be a deciding factor when analysing the costs of an AC-coupled battery.
Complexity: Even though a retrofit is generally easier to install, the overall system can become quite complex as there are more components involved.
Backup Power Limitations: It is also important to note that some AC-coupled batteries lose the ability to charge via solar during grid outages. Most solar inverters need a stable grid connection to remain operational.
Unlike AC-coupled systems, DC-coupled systems are directly integrated with solar systems’ hybrid ‘battery-ready’ inverters like the Fronius Symo GEN24, which can manage solar and battery energy in the one unit.
Based on the system’s settings, the hybrid inverter can decide whether to send the DC energy to charge the battery without conversion or alternatively convert it to AC to supply the home or feed into the grid.
DC-coupled systems are generally preferred for properties with no existing solar, or homes that are getting system replacements as the solar must be connected to a hybrid inverter and meet Australian standards and accreditation.
DC coupled batteries are also ideal for locations with frequent daytime power outages as the system will continue to produce solar and replenish the battery.
Higher Energy Efficiency: Because there are fewer conversions between AC and DC occurring, there are fewer power losses which means that DC-coupled systems are better for efficiency.
Recommended for Off-grid setups: Due to the minimal loss in energy conversions, off-grid systems could reduce losses and maximise production and storage.
Only Option for Off-Grid Setups: DC-coupled battery systems are directly compatible with off-grid inverters, allowing
properties to generate, store, and consume their own electricity.
Requires a Hybrid Inverter: Because DC-coupled systems require a hybrid inverter (or ‘battery-ready inverter’) to control solar, charging, and grid energy all in one unit, these can increase the cost of the total system.
Adaptability: Installing a DC-coupled battery system requires the property’s solar array to meet all current Australian standards and certifications for hybrid inverter connection. This means that older PV arrays may need to be replaced for compatibility purposes.
For off-grid solar systems, DC-coupled configurations are chosen for a few reasons.
They not only provide better energy efficiency with limited conversions, but they are also designed to work seamlessly with off-grid inverters like Selectronic SP PRO’s where they manage both solar and battery in one unit for simplicity.
Because both AC and DC-coupled systems are designed for different purposes, there isn’t a better option for homes across Australia. Finding the right configuration will come down to your property, requirements, and budget.
For homes with existing solar, it may be more cost-effective to retrofit an AC-coupled battery to your solar system.
For homes getting a new solar system, a DC-coupled system might make more sense for longevity and future compatibility.
If you’re looking at getting a battery for your property and are unsure whether an AC or DC-coupled battery would be better, we offer free quoting to help people like you get transparent quoting and consultation.
Determining whether an AC or DC-coupled system is better cost-wise is specific to your property and requirements. The cost of an AC or DC-coupled battery comes down to a few factors like the chosen brands, installation and rectification requirements, and the system’s proximity to your switchboard.
The price differences between DC and AC-coupling battery systems comes down to the design and installation requirements of your property rather than comparing return-on-investments.
Tesla Powerwall 3: AC and DC-coupled
Sungrow SBH: AC and DC-coupled
BYD Battery Box: AC
and DC coupled
What’s the purpose of a Battery Inverter?
Certain batteries are designed for AC-coupling and includes a separate inverter to be used to convert the energy between AC and DC. Battery options like Tesla Powerwall 2 were specifically designed for AC-coupled systems, to be integrated into existing systems.
However, newer battery options like Tesla Powerwall 3 and Sungrow batteries have the ability to be both AC and DC-coupled for the ultimate flexibility. (Sungrow and BYD batteries are generally more popular for DC-coupled systems).
Hybrid Inverters, otherwise known as ‘battery-ready inverters’, are designed for controlling both traditional solar DC and AC inversion and battery storage inversion in the one unit.
With the ability to operate in both on and off-grid situations, a hybrid inverter is capable of seamless transitioning from solar/grid energy to stored battery energy.
Whilst hybrid inverters have fewer compatible battery options, they are generally preferred for backup energy solutions for regular grid outage prone areas due to their seamless transitioning and high energy efficiency.
Deciding whether to get a traditional grid-tied inverter, or a battery-ready hybrid inverter will depend on a few factors like budget, energy requirements, and goals.
If you’re looking at getting battery storage along with your solar system installation or a little after, a hybrid inverter might be the option to choose as you reduce system complexity.
For those who are just looking into solar energy and are not interested in battery storage for the near future, a grid-tied inverter will do the job. Traditional inverters are generally cheaper than their battery-ready counterparts.
If you’re unsure on what components you’ll need for your requirements, let us design the optimal system for your energy goals.
Whilst it initially sounds daunting when you hear ‘AC-coupled 10kW solar and battery system’, with the context of this article, it’s not so bad! Whether you’re an existing solar owner or are looking at getting a system for your property, finding the right solution can be crucial in achieving the goals you require.
Articles like this are designed to better help you make the right decisions when it comes to your energy. For free quoting and consultation, we’d love to have a chat with you and discuss the optimal solution for your requirements.
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