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With more and more homes and businesses looking into battery options with available rebates and incentives, finding the right battery can be a hard venture, with many variables like energy capacity, brands, and models. One aspect in finding the right battery for your home considers whether the battery is AC or DC-coupled, but what does this actually mean, and what's right for your property?
In its simplest form, AC-coupling is when a battery is connected to the AC side of your system, after the inverter. DC-coupling is before the inverter on the DC side.
AC vs. DC-coupling refers to where and how the battery is connected to your solar system. 'Coupling' is another word for connected - AC or DC-'connected' battery storage.
Because DC-coupled battery systems are connected on the DC side of the inverter, it relies on the inverter to convert the DC energy to AC for home consumption. AC-coupled batteries on the other hand have already 'gone through' the inverter, and from DC is converted back to AC via the battery's built-in inverter, independent of the main inverter.
Both DC & AC-coupling are chosen depending on elements like budget, goals, and existing system requirements of 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 | Normal Inverter with battery compatibility | 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 operate independently of solar and inverter generation with its own AC to DC conversion capabilities. Depending on the solar and battery configuration, the solar system generally acts as its own system, providing home AC energy through the inverter, and feeding it into the grid. An AC-coupled system will add to this by storing any excess solar energy that the inverter sends to it.
An AC-coupled battery doesn't need a hybrid inverter, as the built-in inverter is responsible for converting its own energy which means it is better for retrofits and broader compatibility unlike DC-coupled battery systems.
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.
Advantages |
Disadvantages |
|
AC-Coupled Battery Systems |
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. |
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 Systems |
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. |
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. |
Determining on whether an AC-coupled or DC-coupled battery will come down to your unique situation and requirements.
If your home has existing solar without a hybrid solar inverter, an AC-coupled battery may be better suited for you. If you're installing an entirely new solar system, investing in a hybrid DC-coupled battery system is the way to go.
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 highly-recommend contacting your local solar battery installers to determine the right solution for you.
Understanding the difference between alternating current (AC) and direct current (DC) is easier than you might think.
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.
Your solar system and battery both use DC, where your home appliances run on AC electricity, so there needs to be a conversion somewhere to accommodate.
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 also have its own set of requirements which indicate varied costs of installation an AC and DC-coupled battery system.
Most solar and battery storage installers will provide free consultation and quoting to better help you find the best system for you and your property.
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.
The difference between traditional grid-tied and hybrid inverters consists of features and future potential with the ability to upgrade in the future.
Hybrid inverters, otherwise known as ‘battery-ready inverters’, are designed for controlling both traditional solar DC and AC inversion, as well as battery storage inversion all in the one unit.
With the ability to operate in both on and off-grid situations, a hybrid inverter is capable of seamless transitions from grid energy to solar or stored battery energy during outages.
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.
Not every home solar battery will have its own built-in inverter to convert AC and DC. AC-coupled batteries like Tesla Powerwall 2 have their own built-in inverter to have the ability to be retrofitted and AC-coupled to existing solar systems.
Because AC-coupled battery storage is not reliant on the solar 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.
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.
Whether you're an existing solar owner or someone who is looking into getting their first solar system installed, it is definitely recommended to research and determine whether a battery is a good investment for your energy.
Choosing from both DC and AC-coupled systems can both bring benefits to ensure you get a good return on your investment, as well as reliability and future upgrade capabilities.
If you're seriously considering what kind of battery to get, we offer free consultation and quoting for homes and businesses in the Newcastle and Maitland region, with SAA-approved solar and battery designers and installers here ready to help find the optimal, compliant energy system.
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