AC vs. DC-coupled Solar Batteries: Which is Better?⚡2025
Posted 20 Mar
Posted 20 Mar
As Australia shifts in its renewable energy transition, demand is getting higher for solar battery storage for homes and businesses looking to take control of their energy.
When researching battery options, you may have heard of 'AC-Coupled system', or 'DC-coupled battery', but what does this actually mean and which one is right for your property?
In this article, we quickly explain what DC and AC-coupled batteries are, their functionalities, features, and what homes and businesses are best-suited. Whether you're on a research-streak, or about to invest in a battery, this should help you make more informed decisions.
Understanding the difference between alternating current (AC) and direct current (DC) is easier than you might think. We actually made an article around this if you'd like to know more.
Essentially, both AC and DC refer to how the current flows in an electrical current. DC flows in one direction and is used in battery storage, where AC is dynamic and switches directions which is used in your home in power outlets etc.
If you own a solar system, that will be generating a direct current (DC), which is then converted by the inverter to alternating current (AC) to be used by home appliances.
AC and DC-coupling refers to where and how the battery is connected to your solar system. 'Coupling' is another word for connected. AC-'connected' battery storage.
For example, a DC-coupled system is connected to the inverter directly which inverts the energy for it, whereas AC-coupled batteries are independent and can inverter its own energy.
Depending on your property's existing requirements, budget, and goals, installers may opt for an AC-coupled or DC-coupled to best suit your home or business.
| 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 | |
AC-coupled battery systems are units that operate independently of solar generation with its own inversion capabilities.
Generally, solar systems in an AC-coupled setup produces its own power, directly feeding the house with renewable energy, and any excess is either fed into the battery or grid exports for NSW's feed-in-tariff. The battery in this situation is responsible for its own AC and DC inversion for storage and use in the home.
Following the diagram, the existing grid-type, non-hybrid solar inverter is designed to convert that solar generation from solar's DC to the home's required AC. Excess solar energy can be sent to the AC-coupled battery, which the built-in inverter converts the AC back to DC for storage.
Because of the increased amount of conversions between AC and DC, the AC-coupled battery is slightly less-efficient but it typically chosen for existing solar systems with existing solar inverters which aren't usually battery-ready (non-hybrid). If your inverter is non-hybrid, this means the battery cannot be directly connected to the inverter, eliminating the possibility for DC-coupling.
AC-coupled batteries are configured to be integrated and operational independent of your solar system, which is better-suited for retrofitting and broader compatibility.
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 an AC-coupled 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.
DC-coupled battery storage refers to how a battery system can be directly integrated with your solar system through a battery-ready, hybrid inverter like the Fronius Symo GEN24 which manages both the solar and battery system simultaneously.
Depending on how the DC-coupled battery system is configured, the hybrid inverter can decide between sending non-converted DC energy to charge the battery, or inverter it to AC to power home appliances. This makes it more efficient as there are fewer conversions occurring.
Installing a DC-coupled battery is generally recommended for properties that are also looking at getting a new solar system installed too. This ensures that the solar system is fully-integrated with the DC-coupled battery which is great for areas with frequent blackouts, as the solar will continue to recharge the battery.
Higher Energy Efficiency: Due to the fewer conversions between AC and DC, there are fewer power losses which means that DC-coupled have efficiency advantages.
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 properties, DC-coupled battery storage is chosen because of seamless integration with off-grid solar inverters like Selectronic SP PRO's, which manages both solar and battery in the one unit.
Whilst it's not a dealbreaker, knowing you're getting the absolute most efficiency out of your solar system is always ideal.
Determining on whether an AC-coupled or DC-coupled battery will come down to your unique situation and requirements
As both AC-coupled and DC-coupled batteries are designed for different purposes, there isn't a better option for all homes and businesses.
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.
Both AC and DC-coupled batteries will have their own unique costs including installation labour requirements desired brands and models, capacities, as well as rectification and additional components required.
Each property will have its own set of requirements which indicate varied costs of installation an AC and DC-coupled battery system.
The good news is that you can get free quoting, as well as free consultation and proposals to help you find the best solution possible.
It can be hard to find information on what batteries are AC-coupled and DC-coupled, so we've listed the batteries we install below and their coupling. To have DC-coupling available for your property, you will need a hybrid inverter (more in this later).
With 13.5kWh of energy capacity, Tesla Powerwall 2 is designed to be AC-coupled for homes in NSW. Tesla Powerwall 2 has a built-in inverter which can invert DC and AC.
Also offering 13.5kWh of energy capacity, Tesla Powerwall 3 can be both AC-coupled and DC-coupled. With a built-in solar inverter, Tesla Powerwall 3 doesn't need an external inverter.
Sungrow's SBH series provides an energy capacity range from 20kWh to 40kWh on a single stack which can also be either installed as an AC or DC-coupled battery system.
With modular and expandable energy storage options from 8.1kWh to 21.7kWh, BYD Battery-Box can be AC-coupled and DC-coupled to homes in Australia.
AC-coupled batteries like Tesla Powerwall 2 have their own built-in solar inverter to convert between AC and DC on its own.
Because the battery storage is not reliant on the inverter, the unit must be able to convert its own energy to be used for storage of home consumption.
Newer battery storage like Tesla Powerwall 3 offer both AC and DC-coupling solutions to enable a wide variety of flexibility in solar and battery configurations.
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 for a reduction in 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.
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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