AC Coupling 2025: Complete Guide 6 Hybrid Inverter Configurations

AC Coupling: the flexible solution for adding storage

With the rise of solar energy storage in Belgium and France, the AC coupling technique is emerging as a flexible solution for adding batteries to an existing photovoltaic installation. Unlike DC coupling, where the panels are connected to the batteries via a single hybrid inverter, AC Coupling involves connecting a charger-inverter (hybrid) on the AC side in parallel with an existing PV inverter.

In practice, the panel array remains connected to its original grid inverter (Fronius, SMA, Huawei, micro-inverters...), and the hybrid inverter with batteries is connected to the electrical panel in AC parallel. This architecture allows you to keep your initial PV installation unchanged on the DC side, while adding storage and energy autonomy.

“AC coupling offers universal compatibility: all your inverters working together via the home grid, with intelligent energy management for storage, backup, and financial optimization.” – Wattuneed Technical Department

This comprehensive guide explores the 6 possible configurations and scenarios for AC Coupling in 2025, their advantages, technical challenges, and solutions to optimize your self-consumption. Whether you have a single-phase or three-phase system, a grid with or without neutral, a mix of inverters from different brands (Deye, Sofar, Fronius, SMA...), this guide will help you master AC coupling professionally.

Configuration 1: Simple AC Coupling grid-tie inverter + hybrid inverter

The first configuration is the most common and easiest to implement: adding a hybrid inverter to an existing photovoltaic inverter. If you already have a grid-tied inverter (called grid-tie or string inverter) for your panels, you can add a hybrid inverter (or charger-inverter) connected to a battery pack.

Operating principle of simple AC coupling

The two inverters operate in parallel on the home grid:

• The PV inverter injects solar energy in AC and powers the home's instantaneous consumption
• The hybrid inverter draws this AC surplus to charge the battery via AC→DC conversion
• In the evening or as needed, the hybrid reinjects the stored energy (DC→AC) to power the house
• All synchronized while maintaining the internal grid at 230V 50Hz

This solution is ideal for retrofitting an existing solar installation as it avoids touching the DC wiring of the panels. You get the best of both worlds: the high efficiency of the dedicated PV inverter (98-99%), and the flexibility of the hybrid inverter for storage and backup.

Advantages of simple AC coupling

• Quick installation: AC connection only, no modification on the panel DC side
• Universal compatibility: Works with all PV inverters on the market
• PV inverter preserved: Warranty and operation unchanged
• Scalability: Battery capacity can be adjusted as needed
• Backup possible: The hybrid inverter can power essential loads off-grid

In practice, the hybrid monitors the voltage/frequency of the internal grid and charges the battery as soon as a solar surplus is detected. However, you must ensure that the hybrid inverter supports the required charging power and configure good coordination between the two inverters. 🔗 See Deye AC Coupling features

Configuration 2: Multi-inverter AC Coupling (multiple PV + one hybrid)

It is not uncommon to have several PV inverters in service, for example two string inverters on different orientations, or a cluster of micro-inverters on a complex roof. AC Coupling offers great inter-brand compatibility: a Sofar hybrid inverter can recover energy from Enphase micro-inverters, or a Deye hybrid can collaborate with a Huawei inverter.

Multi-inverter coordination principles

As long as all are connected to the same AC panel, the principle remains the same. The hybrid inverter will "see" the sum of PV productions and modulate the battery charge accordingly. The key is coordination and regulation to avoid conflicts.