Adding a Battery to Your Existing Solar Panels: DC vs. AC Coupling – Pros and Cons

In this setup, your system remains AC-coupled:

• The grid-tied inverter converts PV electricity into AC,
• The energy flows into your home for immediate use,
• Any excess AC is then sent to the hybrid inverter, which converts it back into DC to charge the battery,
• At night, the battery discharges to power household loads.

✅ Pros:

• No need to remove your existing inverter
• Easier installation
• Saves about AUD 500 in installation costs

❌ Cons:



• Lower efficiency due to multiple energy conversions, with around 5–10% energy loss
• During a grid outage, the grid-tied inverter shuts down, so only the battery powers the backup loads. Once the battery is drained, the system stops entirely—no PV generation or charging.

⚡ Option 2: Remove Grid-Tied Inverter and Connect PV Directly to Storage Inverter (DC Coupling)

This approach is called DC-coupling:

• The PV panels connect directly to the hybrid storage inverter,
• Energy is supplied to loads, and any excess DC power goes straight to the battery (no double conversion),
• In the event of a grid outage, the PV continues to generate, the battery continues to charge and discharge, and backup loads stay powered—a true off-grid-capable system.

✅ Pros:

• Full backup capability during outages: PV, battery, and loads keep running
• High overall efficiency: DC-to-DC charging without conversion losses, up to 98% efficiency

❌ Cons:

• If the existing PV wiring is too short or poorly routed, the installer may need to rewire and reconnect, adding around AUD 500 to installation costs

❓So… DC Couple or AC Couple?

It comes down to your priorities:

• Want a quicker install and lower upfront cost? → AC couple
• Want higher efficiency and real backup functionality? → DC couple

Which one fits your home better?