Smart Coupling: How to Add a Battery Without Wasting Your Existing Solar

Got solar already and thinking about a battery? Your installer will usually offer one of two setups: AC coupling or DC coupling. There's a third option that gets the best of both, and it's called smart coupling.

Here's how each one works, and why smart coupling is often the smartest way to add a battery to an older solar system.

First, why you can't just plug a battery into your old inverter

Most older solar systems use an on-grid (string) inverter. It turns your panels' power into electricity your home can use, but it has no way to charge or run a battery. To add a battery, you need extra equipment. How that equipment connects is what "coupling" means.

Option 1: AC coupling

AC coupling keeps your old solar inverter and adds a battery with its own separate inverter. Both connect to your switchboard.

The upside: you keep your existing solar setup, and it's usually simple to install.

The catch: in a blackout, your old solar inverter is required to switch off for safety. So during an outage you're running on whatever is left in the battery, with no solar topping it up. On a long outage, the battery eventually runs flat, even on a sunny day.

Option 2: DC coupling

DC coupling replaces your old solar inverter with a new hybrid inverter that runs both your panels and your battery.

The upside: it's efficient, and your panels can keep charging the battery during a blackout.

The catch: your old inverter gets thrown out, even if it's still working. On larger or older systems, your existing panels may not suit the new inverter, which can mean extra cost or a smaller system.

Option 3: Smart coupling

Smart coupling combines both. We install a new hybrid inverter and battery, and connect your existing solar inverter to the hybrid inverter's smart port, rather than straight to the grid.

That changes what happens in a blackout. When the grid goes down, the hybrid inverter creates its own mini grid for your home. Your old solar inverter sees that mini grid and keeps running. So both your old panels and any new panels keep powering your home and charging your battery, even during an outage.

When the battery is full and your home doesn't need more power, the hybrid inverter tells the old inverter to throttle back, so nothing is overloaded.

Why smart coupling makes sense for older solar

• Nothing goes to waste. Your existing panels and inverter stay in use, instead of being removed.
• More solar in a blackout. Your old panels keep charging the battery during outages, so your backup lasts longer.
• Room to grow. You can add new panels to the hybrid inverter while keeping the old ones.
• A bigger inverter where it counts. A hybrid inverter of 8kW or more lets you run more appliances at once, and soak up more of a free power window if your plan has one.

Is smart coupling right for your home?

It depends on your existing inverter, its age and condition, your switchboard and how much backup you want. Not every old inverter is suitable, so we check it at your free assessment before recommending the right setup.

Thinking about a battery for your existing solar? Call Aussie Solar Batteries on 1800 975 270, or send us a photo of your inverter and your latest power bill, and we'll tell you whether smart coupling suits your home.

Frequently asked questions