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"Coupling" describes where a battery sits in your solar system's conversion chain. This explainer covers how each architecture works and the mechanics behind the efficiency trade-off. Weighing up which to buy? Our AC vs DC coupled battery comparison puts the two head-to-head for Perth homes.
Quick answer
DC-coupled batteries store solar before it is converted, so a single conversion step delivers about 95% round-trip efficiency, and they suit new solar-plus-battery installations. AC-coupled batteries connect after your existing solar inverter at about 90% round-trip efficiency, which makes them the retrofit-friendly choice because your current inverter stays in place. For most households the practical difference is a few percent in savings, so existing equipment often matters more than the coupling type.
Solar panels generate DC (direct current) electricity. Your home uses AC (alternating current). The question is: where does your battery sit in this conversion process?
Battery connects before the inverter
Battery connects after the inverter
DC-coupled batteries connect directly to your solar panels through a hybrid inverter. Solar energy flows as DC from panels → battery → inverter → home. There's only one conversion step (DC to AC).
AC-coupled batteries connect to your home's AC circuit, after the solar inverter. Solar energy converts DC→AC at the solar inverter, then AC→DC to charge the battery, then DC→AC again when discharging. Multiple conversions each way.
Single conversion step minimises losses
Multiple conversions result in higher losses
The efficiency difference is real but relatively small. For most households, the practical impact is a few percent difference in savings. Other factors like existing infrastructure often matter more.
Backup power note
Whether a system provides backup power during a blackout depends on the complete system design, not on the coupling type alone. Both AC and DC coupling can support backup power; the implementation differs. Discuss your backup requirements specifically with your installer.
If you installed solar in the last 5-10 years, you likely have a quality string inverter with remaining warranty. AC-coupling lets you add a battery while keeping your existing setup intact. DC-coupling would typically require replacing your inverter.
Synergy's VPP programs work with both AC and DC coupled systems. Eligibility depends on the specific battery and system configuration, not the coupling type. Confirm your specific setup is eligible with your installer.
For the full side-by-side on costs, which battery brands use each type, and the WA retrofit path, compare AC and DC coupled batteries.
"Is AC or DC coupling better for my existing setup?"
They should assess your current inverter and recommend based on your situation.
"What's the practical efficiency difference for my usage?"
The real-world impact depends on how you use energy.
"What happens if I want to expand the system later?"
Understand how each option affects future flexibility.
"How does backup power work with this configuration?"
If backup matters to you, understand the specific implementation.
Answer six questions about your home and energy use, and we'll rank batteries by ROI and fit — including guidance on whether AC or DC coupling suits your setup.
Explore your optionsAS/NZS 5139 clearance rules, garage vs outdoor walls, and what installers check on-site.
A step-by-step method covering evening usage and seasonal AC demand.
Activation events credit 70¢/kWh on top of DEBS exports, and signing up is a WA rebate condition.
Answer a few questions and see systems and installers that fit your home.